# New Casemix Classification as an Alternative Method for Budget Allocation in Thai Oral Healthcare Service: A Pilot Study

Authors: Thunthita Wisaijohn; Atiphan Pimkhaokham; Phenkhae Lapying; Chumpot Itthichaisri; Supasit Pannarunothai; Isao Igarashi; Koichi Kawabuchi
Journal: International Journal of Dentistry
 (2010)

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## Abstract

This study aimed to develop a new casemix classification system as an alternative method for the budget allocation of oral healthcare service (OHCS). Initially, the International Statistical of Diseases and Related Health Problem, 10th revision, Thai Modification (ICD-10-TM) related to OHCS was used for developing the software “Grouper”. This model was designed to allow the translation of dental procedures into eight-digit codes. Multiple regression analysis was used to analyze the relationship between the factors used for developing the model and the resource consumption. Furthermore, the coefficient of variance, reduction in variance, and relative weight (RW) were applied to test the validity. The results demonstrated that 1,624 OHCS classifications, according to the diagnoses and the procedures performed, showed high homogeneity within groups and heterogeneity between groups. Moreover, the RW of the OHCS could be used to predict and control the production costs. In conclusion, this new OHCS casemix classification has a potential use in a global decision making.


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## Body

## 1. Introduction

There are many insurance systems worldwide for Universal Healthcare Coverage. In Thailand, health insurance systems are categorized into three major schemes: the Civil Servant Medical Benefit Scheme (CSMBS), the Social Security Scheme (SSS), and the Universal Coverage Scheme (UCS) or the “30 baht (in 2002, 43.0 Baht/US$ copayment) for all diseases” (UCS was implemented in May 2001 and introduced nationwide in April 2002) [1]. In 2006, the UCS abolished the 30 baht copayment per visit and made the UCS free [2]. In the past, the health budget was allocated by the characteristics of each healthcare provider, the number of doctors, and the number of patient beds. Thus, healthcare resources were not equitably allocated between the health insurance systems [3]. In 2001, the revamping of the health insurance system was initiated to restructure the methodology and the system allocating healthcare resources by the Health Systems Research Institute [4, 5]. One key difference between the insurance schemes is that the UCS separated the provider budget between the inpatient and the outpatient for exclusive capitation. Under this paradigm, the outpatient budget was allocated on the basis of the capitation rate, while the inpatient budget was allocated on the basis of Diagnosis Related Group (DRG) within a global budget [1].Under the UCS, the budget for the oral healthcare service (OHCS), based on the benefit package, is part of the outpatient and Promotion/Prevention budget, to share financial risks among OHCS and general health services. While the budgets for all capital investment budgets are allocated by the Ministry of Public Health (MOPH) regional regulators’ judgment, the OHCS, unfortunately, is usually the last priority. Therefore, the efficiency of the allocation is doubted, mainly the methodology and reliability aspect, as follows: (1) Since the Universal Healthcare Coverage policy was established in the year 2001, the demands for government-funded OHCS have increased significantly. In particular, the demand for dental substitution, which is highly expensive, has increased [6]. The per capita budget for all healthcare service in the fiscal year of 2003 was the same amount as the previous year, approximately 1,202 baht (43.0 Baht/US$) [7, 8] and became 2,202 Baht (34.34 Baht/US$) in 2009. (2) Current budget allocation has not been categorized for OHCS separately, and there have been few cost studies of OHCS. The information on the cost of these service activities is scarce, leading to a shortage of information for making management decisions. Thus, cost studies of OHCS are important and necessary for the evaluation of healthcare managerial efficiency and resource allocation, as well as for generating the appropriate parameters to use in making policies for healthcare service improvement in the context of budgetary constraints [9, 10].Casemix is a generic term for the patients’ classification system, including inpatient and outpatient status, budgeting allocation, and payment [11]. Successful outcomes from the adoption of a casemix system have been shown in many countries [12–14]. The best-known classification system used in a casemix funding model is the DRG. The DRG classifies acute inpatient episodes into a discrete number of manageable categories, depending on their clinical condition and resource consumption, assigned by a grouper program based on their demographics, clinical information (diagnosis (Dx) and procedure (Proc) codes), and comorbidity. The DRG method has been well evaluated for classifying inpatient treatment [15, 16]. In Thailand, the initial DRG was implemented in 1999 and several successive versions have been developed. Pannarunothai’s studies on DRG development in Thailand recommended that casemix systems should be used in the budget allocation for the healthcare service system [11, 17].In Thailand, most people are covered by the aforementioned insurance schemes, although the budget allocations and payment systems are different between the schemes. DRG is currently employed as an allocation method only for inpatient healthcare budgets and not for all healthcare budgets. However, the DRG system has limitations in reflecting the OHCS cost. The future development of the appropriate inpatient and outpatient casemix for OHCS is important and necessary for economic healthcare management [17].For the above-described reasons, the development of a new casemix classification in OHCS is desirable. This study aimed to develop and examine the feasibility of a new casemix classification system as an alternative method for budget allocation in Thai OHCS. These three schemes were each adapted, on the basis of DRG, as an alternative method to inpatient and outpatient-related OHCS for budget allocation [11, 18, 19]. This system might, in time, be applied in other countries healthcare system for OHCS resource allocation as well.


## 2. Materials and Methods

This study was conducted utilizing the electronic data of individual patients treated from April 2008 to March 2009 at three selected tertiary hospitals that met the study’s inclusion criteria. The study protocol was approved by the Ethics Committee of the participating hospitals. The inclusion criteria were the use of the International Classification of Diseases, 10th edition (ICD-10) and International Classification of Disease, 9th edition, Clinical Modification (ICD-9-CM) for the clinical records [20, 21] and the systematic keeping of a database record that was based on a global coding of the clinical records. These databases contained information on inpatient and outpatient care utilization, including demographic data (date of birth (DOB), age, and gender), clinical information (Dx, Proc), and resource consumption (hospital charge, admission date, discharge date and type, length of stay (LOS), and health insurance). The five main methods used to develop a new casemix classification as an alternative method for budget allocation of OHCS in this study were coding, classification, costing, calibration, and payment.


### 2.1. Coding

The coding process was divided into two parts.Part I
The development of the new casemix classification for OHCS began with the adoption of the ICD-10, ICD-9-CM, Current Dental Terminology 2007 (CDT) [22], International Statistical of Diseases and Related Health Problem, 10th revision, Thai Modification (ICD-10-TM) [23, 24], Thai DRG version 4 [25], and International Refined DRG (IR-DRG) [26]. The study designed the analysis method in two steps. Step one, the ICD-10-TM for Dx and Proc codes related to OHCS were retrieved by a researcher and approved by five dentists with more than ten years of clinical experience and specialists in OHCS. Step two, these codes were then mapped to ICD-10 for Dx and ICD-9-CM for Proc by Program Map version 1.0, copyright of Thai health coding center, Cluster for Health Information Division, Bureau of Policy and Strategy, MOPH, Thailand. These selected codes were used as inclusion lists of principal diagnoses (PDx) and procedures (Proc).Part II
The electronic data of individual patients from the three selected tertiary hospitals were checked based on the inclusion lists of PDx and Proc (Figure1).Figure 1
Diagram presents the steps one and two.


### 2.2. Classification

To develop a new casemix classification system for Thai OHCS, a specially designed computer software program called “Grouper” was used. Grouper was able to allocate each episode to a DRG according to the clinical information and other relevant data. This program used clinical and demographic data as the input and produced a corresponding DRG as the output [27].The OHCS casemix classification model (Grouper) consisted of one procedure in one visit that classified cases into two main groups: the oral and maxillofacial surgery (OMFS) group, designated M, and the tooth and periodontium group, designated D. Multiple procedures in one visit were designated as P. The variables used for the OHCS grouping were included (1) PDx, (2) secondary diagnosis (SDx), (3) Proc (which were classified by the level of complexity by the same expert group), (4) anatomy group by body regions related to ICD-10-TM (Table1), (5) root operation related to ICD-10-TM (Table 2), (6) general anesthesia (GA), and (7) complication and comorbidity (CC), using the Charlson index. This classification system was developed to allow the translation of dental procedures into eight-digit codes as summarized in Figures 2, 3, 4, and 5.Table 1
Examples of both groups (M and D), split into procedure clusters using the anatomy group by body region.
OMFS groups (anatomical body region)Code MScalpInclude: scalp and subgaleal soft tissuesM01SkullM02Cranial nerves X, Trigeminal nerveM03Cranial nerves X1, Accessory nerveM04Cranial nerve XII, Hypoglossal nerveM05Cranial nervesM06FaceM07MaxillaM08MandibleM09Tooth and periodontium group (anatomical body region)Code DOral examinationD01Radiographs/Diagnostic imagingD02Preventive dentistryD03Oral hygiene instructions and counselingD04Tooth restorationD05Endodontic treatmentD06M: oral and maxillofacial surgery (OMFS) corrects a wide spectrum of diseases, injuries, and defects in the head, neck, face, jaws, and the hard and soft tissues of the oral and maxillofacial region.D: tooth and periodontium: periodontium refers to the specialized tissues that surround and support the teeth (small, calcified, whitish structures found in the jaws (or mouth)) maintaining them in the maxilla and mandible.Table 2
Examples of the procedure clusters, split into subgroups of procedure clusters using a root operation.
OMFS groups (root operation)Code MScalpInclude: scalp and subgaleal soft tissuesM01Diagnostic procedures and non-operative proceduresM0101Operative proceduresM0102Miscellaneous proceduresM0104Other procedures and operationsM0199Tooth and periodontium (root operation)Code DOral examinationD01Oral  examination proceduresD0121Radiographs/Diagnostic imagingD02Intraoral filmD0222Extraoral filmD0223OthersD0299M: oral and maxillofacial surgery (OMFS).D: tooth and periodontium.Figure 2
Diagram presents the casemix classification model of OHCS (one procedure in one visit) as represented in eight-digit codes.Figure 3
Diagram demonstrates the overviews of the Thai oral healthcare service (OHCS) casemix classification model of one procedure in one visit. M = oral and maxillofacial surgery (OMFS), W = with, W/O = without, GA = general anesthesia, CC = complication and comorbidity.Figure 4
Diagram presents the casemix classification model of OHCS (multiple procedures in one visit) as represented in eight-digit codes.Figure 5
Diagram demonstrates overviews of the Thai oral healthcare service (OHCS) casemix classification model of multiple procedures in one visit (P). M = oral and maxillofacial surgery (OMFS), W = with, W/O = without, GA = general anesthesia, CC = complication and comorbidity.


### 2.3. Costs

Initially, multiple regression analysis was used to study the relationship between the factors used for developing the codes and resource consumption. This analysis was employed to explore the relationship between the cost of P, D, and M (dependent variables) and several independent variables including, GA, CC, number of procedures in one visit, Proc (separated by the level of complexity), and LOS. Cross-validation was used to test the validation of the casemix in a separate set of data. Cross-validation showed the quality of the prediction equation between the structure data and the data for validation. The higher confidence obtained from the cross-validation, the more suitable the estimation of the population prediction equation.


### 2.4. Calibration

Three statistical analyses, the coefficient of variation (CV), the reduction in variance (RIV), and the relative weight (RW), were applied to verify the minimum variation within each group, the maximum variation among groups, and the assignment of a payment weight for the new casemix classification, respectively.The CV is calculated as the standard deviation divided by the arithmetic mean. The CV value demonstrates the homogeneity of the cases within each group. A high CV indicates wide variation within each group. The accepted standard for CV is that each class should have a CV of less than 1.0 [15]. The expected end results using the new grouper program are groups of cases that are clinically similar and/or homogeneous with respect to resource use.The RIV statistic is commonly used to assess the overall performance of the grouping method by comparing the variances of cost before and after grouping. The RIV was also related to the amount of variation within the data that requires explanation. A higher RIV reflected better performance of the grouping.The RW is a measure of the resources used: it compares the average resource used in each group with the average resource used in all cases. In this study, statistical outliers beyond three standard deviations of the average cost for each OHCS classification were eliminated [28–30]. The RW was computed based on the cost data. It was defined in our study as the mean cost in each group divided by the mean costs of all patients. The cost in this study focused only on the cost of surgery, including general and local anesthesia, medical devices and instruments, and medical supplies. The staff cost was not included in this study because it was not paid on a per case basis. In Thailand, all staff salary is paid by the government and is dependent on the degree of education and the years of experience. Furthermore, the standard of staff cost has not been well established in Thailand.


### 2.5. Payment

A payment calculation was necessary to establish the prospective payment system. The payment was calculated using the RW of the OHCS classification multiplied by the current reimbursement rate (average base rate) in each group.


## 2.1. Coding

The coding process was divided into two parts.Part I
The development of the new casemix classification for OHCS began with the adoption of the ICD-10, ICD-9-CM, Current Dental Terminology 2007 (CDT) [22], International Statistical of Diseases and Related Health Problem, 10th revision, Thai Modification (ICD-10-TM) [23, 24], Thai DRG version 4 [25], and International Refined DRG (IR-DRG) [26]. The study designed the analysis method in two steps. Step one, the ICD-10-TM for Dx and Proc codes related to OHCS were retrieved by a researcher and approved by five dentists with more than ten years of clinical experience and specialists in OHCS. Step two, these codes were then mapped to ICD-10 for Dx and ICD-9-CM for Proc by Program Map version 1.0, copyright of Thai health coding center, Cluster for Health Information Division, Bureau of Policy and Strategy, MOPH, Thailand. These selected codes were used as inclusion lists of principal diagnoses (PDx) and procedures (Proc).Part II
The electronic data of individual patients from the three selected tertiary hospitals were checked based on the inclusion lists of PDx and Proc (Figure1).Figure 1
Diagram presents the steps one and two.


## 2.2. Classification

To develop a new casemix classification system for Thai OHCS, a specially designed computer software program called “Grouper” was used. Grouper was able to allocate each episode to a DRG according to the clinical information and other relevant data. This program used clinical and demographic data as the input and produced a corresponding DRG as the output [27].The OHCS casemix classification model (Grouper) consisted of one procedure in one visit that classified cases into two main groups: the oral and maxillofacial surgery (OMFS) group, designated M, and the tooth and periodontium group, designated D. Multiple procedures in one visit were designated as P. The variables used for the OHCS grouping were included (1) PDx, (2) secondary diagnosis (SDx), (3) Proc (which were classified by the level of complexity by the same expert group), (4) anatomy group by body regions related to ICD-10-TM (Table1), (5) root operation related to ICD-10-TM (Table 2), (6) general anesthesia (GA), and (7) complication and comorbidity (CC), using the Charlson index. This classification system was developed to allow the translation of dental procedures into eight-digit codes as summarized in Figures 2, 3, 4, and 5.Table 1
Examples of both groups (M and D), split into procedure clusters using the anatomy group by body region.
OMFS groups (anatomical body region)Code MScalpInclude: scalp and subgaleal soft tissuesM01SkullM02Cranial nerves X, Trigeminal nerveM03Cranial nerves X1, Accessory nerveM04Cranial nerve XII, Hypoglossal nerveM05Cranial nervesM06FaceM07MaxillaM08MandibleM09Tooth and periodontium group (anatomical body region)Code DOral examinationD01Radiographs/Diagnostic imagingD02Preventive dentistryD03Oral hygiene instructions and counselingD04Tooth restorationD05Endodontic treatmentD06M: oral and maxillofacial surgery (OMFS) corrects a wide spectrum of diseases, injuries, and defects in the head, neck, face, jaws, and the hard and soft tissues of the oral and maxillofacial region.D: tooth and periodontium: periodontium refers to the specialized tissues that surround and support the teeth (small, calcified, whitish structures found in the jaws (or mouth)) maintaining them in the maxilla and mandible.Table 2
Examples of the procedure clusters, split into subgroups of procedure clusters using a root operation.
OMFS groups (root operation)Code MScalpInclude: scalp and subgaleal soft tissuesM01Diagnostic procedures and non-operative proceduresM0101Operative proceduresM0102Miscellaneous proceduresM0104Other procedures and operationsM0199Tooth and periodontium (root operation)Code DOral examinationD01Oral  examination proceduresD0121Radiographs/Diagnostic imagingD02Intraoral filmD0222Extraoral filmD0223OthersD0299M: oral and maxillofacial surgery (OMFS).D: tooth and periodontium.Figure 2
Diagram presents the casemix classification model of OHCS (one procedure in one visit) as represented in eight-digit codes.Figure 3
Diagram demonstrates the overviews of the Thai oral healthcare service (OHCS) casemix classification model of one procedure in one visit. M = oral and maxillofacial surgery (OMFS), W = with, W/O = without, GA = general anesthesia, CC = complication and comorbidity.Figure 4
Diagram presents the casemix classification model of OHCS (multiple procedures in one visit) as represented in eight-digit codes.Figure 5
Diagram demonstrates overviews of the Thai oral healthcare service (OHCS) casemix classification model of multiple procedures in one visit (P). M = oral and maxillofacial surgery (OMFS), W = with, W/O = without, GA = general anesthesia, CC = complication and comorbidity.


## 2.3. Costs

Initially, multiple regression analysis was used to study the relationship between the factors used for developing the codes and resource consumption. This analysis was employed to explore the relationship between the cost of P, D, and M (dependent variables) and several independent variables including, GA, CC, number of procedures in one visit, Proc (separated by the level of complexity), and LOS. Cross-validation was used to test the validation of the casemix in a separate set of data. Cross-validation showed the quality of the prediction equation between the structure data and the data for validation. The higher confidence obtained from the cross-validation, the more suitable the estimation of the population prediction equation.


## 2.4. Calibration

Three statistical analyses, the coefficient of variation (CV), the reduction in variance (RIV), and the relative weight (RW), were applied to verify the minimum variation within each group, the maximum variation among groups, and the assignment of a payment weight for the new casemix classification, respectively.The CV is calculated as the standard deviation divided by the arithmetic mean. The CV value demonstrates the homogeneity of the cases within each group. A high CV indicates wide variation within each group. The accepted standard for CV is that each class should have a CV of less than 1.0 [15]. The expected end results using the new grouper program are groups of cases that are clinically similar and/or homogeneous with respect to resource use.The RIV statistic is commonly used to assess the overall performance of the grouping method by comparing the variances of cost before and after grouping. The RIV was also related to the amount of variation within the data that requires explanation. A higher RIV reflected better performance of the grouping.The RW is a measure of the resources used: it compares the average resource used in each group with the average resource used in all cases. In this study, statistical outliers beyond three standard deviations of the average cost for each OHCS classification were eliminated [28–30]. The RW was computed based on the cost data. It was defined in our study as the mean cost in each group divided by the mean costs of all patients. The cost in this study focused only on the cost of surgery, including general and local anesthesia, medical devices and instruments, and medical supplies. The staff cost was not included in this study because it was not paid on a per case basis. In Thailand, all staff salary is paid by the government and is dependent on the degree of education and the years of experience. Furthermore, the standard of staff cost has not been well established in Thailand.


## 2.5. Payment

A payment calculation was necessary to establish the prospective payment system. The payment was calculated using the RW of the OHCS classification multiplied by the current reimbursement rate (average base rate) in each group.


## 3. Results

### 3.1. Coding

Part I (Steps One and Two)
The ICD-10-TM, consisting of 813 diagnoses and 1,090 procedures related to OHCS, were retrieved and mapped to ICD-10 and ICD-9-CM, respectively.Part II
The electronic data of individual patients from three selected tertiary hospitals were checked by an inclusion list of PDx and Proc. There were 16,165 (84.64%) cases out of 19,098 initial cases (cases with incomplete data were eliminated) that met the inclusion criteria. The number of inpatient and outpatient cases were 2,709 (16.8%) and 13,456 (83.2%), respectively. The demographic details, clinical information and health insurance showed that the majority of the patients were female (8,723 cases; 54.0%), non-GA (13,911 cases; 86.05%), non-CC (15,708 cases; 97.17%), and CSMBS (6,368 cases; 39.4%).


### 3.2. Classification

The new OHCS casemix classification model (Grouper) consisted of two major procedure categories, M and D, 62 procedure clusters (Table1), 165 subgroups of procedure clusters (Table 2), and 1,624 OHCS classifications according to the treatment procedures (Annex Table 5). Each OHCS classification described a cluster of patients with related diagnoses, requiring a similar examination and incurring similar treatment costs.  There were 16,165 patients who were grouped into OHCS classifications by the grouper software. After the grouping process, only 307 OHCS classifications were achieved to cover these procedure codes. This result was likely limited by the OHCS data, as the amount available in this pilot study was not sufficient to support the OHCS grouper.


### 3.3. Costs

For predicting costs, regression analysis was employed. Table3 presents the determination of the cost of P, D, and M. Because cost did not present a normal distribution, a normal logarithmic transformation was undertaken. The predicted cost of P, D, and M had R2values of 0.892, 0.132, and 0.122, respectively, and the probability of the F-test statistic was 0.000. The results showed that the GA, CC, number of procedures in one visit, Proc (divided by the level of complexity), and LOS were associated with the costs of P, D, and M.Table 3
Multiple regressions of the cost of multiple procedures (P), the cost of OMFS (M), and the cost of tooth and periodontium (D).
Cost of multiple procedures (P)Cost of OMFS (M)Cost of tooth and periodontium (D)95% CI95% CI95% CIOdds-ratioLower-upperP-valueOdds-ratioLower-upperP-valueOdds-ratioLower-upperP-valueGenderMale (reference)Female0.970.89–1.13.9731.141.02–1.19.0090.950.88–1.03.243Age0–22 (reference)23–401.040.89–1.22.6711.561.39–1.74<.0011.020.91–1.15.63341–540.880.75–1.03.1211.171.05–1.31.040.820.73–0.92.00154 +0.850.73–0.99.0391.171.15–1.30.030.790.71–0.88<.001GANon-GA (reference)GA295.78162.41–538.67<.0011.571.49–1.66<.0012386.74891.84–6387.39<.001Number of procedures1 (reference)29.558.72–12.45.0331.021.01–1.03<.0011.021.01–1.02<.00132.721.35–4.56<.0011.211.16–1.28<.0011.191.14–1.23<.00148.686.78–11.34<.0011.161.12–1.20<.0011.161.13–1.27<.001CCNon-CC (reference)CC3.252.31–4.57<.0011.171.10–1.31<.00115.7611.25–21.96<.001Complexity1 (reference)2-33.812.31–4.57<.0011.911.89–1.92<.0011.911.89–1.92<.001LOSLE21 (reference)GE220.150.06–0.33<.0011.531.38–1.73<.0010.020.05–0.08<.001Adjusted cost of multiple procedures (P)R2=0.892, cost of OMFS (M) R2=0.122, and cost of tooth and periodontium (D) R2=0.132GA = general anesthesia, Number of procedures = total procedures in one visit, CC = complication and comorbidityComplexity = level of complexity (1 = simple procedure, 2 = complex procedure, 3 = multidisciplinary or complicated procedure)LOS = length of stay (LE21 = less than and equal to 21, GE22 = more than 21).


### 3.4. Calibration

To ensure that the OHCS classifications reflected resource homogeneity within groups and heterogeneity between groups, the CV and RIV, respectively, were used for analysis.The lowest CVs relative to the outpatient groups for P, D, and M were 0.02 (P2110200), 0.01 (D0843200), and 0.19 (M4004100), respectively, while the highest CVs relative to these groups for P, D, and M were 0.87 (P2020500), 0.99 (D0736200), and 0.83 (M4310101), respectively. The lowest CVs relative to the inpatient groups for P, D, and M were 0.31 (P2200511), 0 (the number of cases was less than five), and 0.22 (M4004100), respectively, while the inpatients’ highest CVs for P, D, and M were 0.98 (P2200410), 0 (the number of cases was less than five), and 0.99 (M3002110), respectively. Moreover, all OHCS classifications had a CV on cost of less than one (Table4, Annex Table 5).Table 4
Summary of the statistical analysis of the coefficient of variation (CV), reduction in variance (RIV), and relative weight (RW).
OHCSN (cases)CVRIVRWInpatientOutpatientInpatientOutpatientInpatientOutpatientInpatientOutpatientP3657,8320.31–0.980.02–0.8716%27%0.13–2.030.51–3.59D32,619N/A0.01–0.99N/A87%N/A0.14–21.33M2,3413,0050.22–0.990.19–0.8322%65%0.02–3.460.30–7.88P = multiple procedures in one visit, D = tooth and periodontium, M = oral and maxillofacial surgery (OMFS)CV = coefficient of variation, RIV = reduction in variance, RW = relative weight, N/A = not applicable.Table 5
Demonstrates examples of the oral healthcare service (OHCS) groupers.
Description of oral healthcare service (OHCS) classificationsWithout GAWithout GAWith GAWith GAwithout CCwith CCwithout CCwith CCSkull, Operative procedures, level 3M0202300M0202301M0202310M0202311Face, Operative procedures, level 1M0702100M0702101M0702110M0702111Maxilla, Operative procedures, level 1M0802100M0802101M0802110M0802111Maxilla, Operative procedures, level 2M0802200M0802201M0802210M0802211Maxilla, Operative procedures, level 3M0802300M0802301M0802310M0802311Mandible, Diagnostic procedures and nonoperative procedures, level 1M0901100M0901101M0901110M0901111Mandible, Diagnostic procedures and nonoperative procedures, level 2M0901200M0901201M0901210M0901211Mandible, Diagnostic procedures and nonoperative procedures, level 3M0901300M0901301M0901310M0901311Mandible, Operative procedures, level 1M0902100M0902101M0902110M0902111Mandible, Operative procedures, level 2M0902200M0902201M0902210M0902211Mandible, Operative procedures, level 3M0902300M0902301M0902310M0902311Facial bone, Operative procedures, level 2M1002200M1002201M1002210M1002211Facial bone, Operative procedures, level 3M1002300M1002301M1002310M1002311Nose, Repair or reconstruction, level 1M1906100M1906101M1906110M1906111Nose, Other procedures and operations, level 1M1999100M1999101M1999110M1999111Nasal cavity, Removal and replacement of nasal packing and Control of epistaxis level 1M2009100M2009101M2009110M2009111Nasal cavity, Other procedures and operations, level 1M2099100M2099101M2099110M2099111Nasal cavity, Other procedures and operations, level 2M2099200M2099201M2099210M2099211Nasal septum, Repair or reconstruction, level 3M2206300M2206301M2206310M2206311Frontal nasal sinuses, Repair or reconstruction, level 1M2306100M2306101M2306110M2306111Frontal nasal sinuses, Repair or reconstruction, level 2M2306200M2306201M2306210M2306211Frontal nasal sinuses, Repair or reconstruction, level 3M2306300M2306301M2306310M2306311Paranasal sinuses, Incision and Excision or destruction, level 1M2504100M2504101M2504110M2504111Parotid salivary gland, Incision and Excision or destruction, level 1M2604100M2604101M2604110M2604111Parotid salivary gland, Incision and Excision or destruction, level 2M2604200M2604201M2604210M2604211Salivary gland and duct, Incision and Excision or destruction, level 1M2804100M2804101M2804110M2804111Salivary gland and duct, Incision and Excision or destruction, level 2M2804200M2804201M2804210M2804211Neck, Diagnostic procedures and nonoperative procedures, level 1M2901100M2901101M2901110M2901111Neck, Diagnostic procedures and nonoperative procedures, level 2M2901200M2901201M2901210M2901211Neck skin, Diagnostic procedures and nonoperative procedures, level 1M3001100M3001101M3001110M3001111Neck skin, Operative procedures, level 1M3002100M3002101M3002110M3002111Neck skin, Operative procedures, level 2M3002200M3002201M3002210M3002211Neck skin, Operative procedures, level 3M3002300M3002301M3002310M3002311Carotid artery, Operative procedures, level 1M3202100M3202101M3202110M3202111Carotid artery, Operative procedures, level 2M3202200M3202201M3202210M3202211Cervical lymph nodes, Diagnostic procedures and nonoperative procedures, level 1M3301100M3301101M3301110M3301111Cervical lymph nodes, Diagnostic procedures and nonoperative procedures, level 2M3301200M3301201M3301210M3301211Thyroglossal reminant, Incision and Excision or destruction, level 1M3504100M3504101M3504110M3504111Thyroglossal reminant, Incision and Excision or destruction, level 2M3504200M3504201M3504210M3504211Lip, Incision and Excision or destruction, level 1M3604100M3604101M3604110M3604111Lip, Incision and Excision or destruction, level 2M3604200M3604201M3604210M3604211Lip, Repair or reconstruction, level 1M3606100M3606101M3606110M3606111Lip, Repair or reconstruction, level 2M3606200M3606201M3606210M3606211Floor of mouth, Incision and Excision or destruction, level 1M3804100M3804101M3804110M3804111Mouth, Diagnostic procedures and nonoperative procedures, level 1M3901100M3901101M3901110M3901111Mouth, Miscellaneous procedures, level 1M3903100M3903101M3903110M3903111Mouth, Incision and Excision or destruction, level 1M3904100M3904101M3904110M3904111Mouth, Incision and Excision or destruction, level 2M3904200M3904201M3904210M3904211Mouth, Repair or reconstruction, level 1M3906100M3906101M3906110M3906111Tongue, Incision and Excision or destruction, level 1M4004100M4004101M4004110M4004111Deciduous teeth, General procedures, level 1M4210100M4210101M4210110M4210111Permanent teeth, General procedures, level 1M4310100M4310101M4310110M4310111Permanent teeth, General procedures, level 2M4310200M4310201M4310210M4310211Soft palate, Repair or reconstruction, level 1M4606100M4606101M4606110M4606111Soft palate, Repair or reconstruction, level 2M4606200M4606201M4606210M4606211Uvula, Repair or reconstruction, level 1M4706100M4706101M4706110M4706111Uvula, Repair or reconstruction, level 2M4706200M4706201M4706210M4706211Uvula, Other procedures and operations on oral cavity, level 1M4799100M4799101M4799110M4799111Uvula, Other procedures and operations on oral cavity, level 2M4799200M4799201M4799210M4799211Uvula, Other procedures and operations on oral cavity, level 3M4799300M4799301M4799310M4799311Oral examination, Oral  examination procedures, level 1D0121100D0121101D0121110D0121111Radiographs/Diagnostic imaging, Intraoral film, level 1D0222100D0222101D0222110D0222111Radiographs/Diagnostic imaging, Extraoral film, level 1D0223100D0223101D0223110D0223111Preventive Dentistry, Preventive Dentistry procedures, level 1D0324100D0324101D0324110D0324111Tooth Restoration, Amalgam restorations (including polishing), level 1D0526100D0526101D0526110D0526111Tooth Restoration, Resin-based composite restorations, level 1D0527100D0527101D0527110D0527111Tooth Restoration, Resin-based composite restorations, level 2D0527200D0527201D0527210D0527211Tooth Restoration, Crown-single restorations only, level 1D0530100D0530101D0530110D0530111Tooth Restoration, Crown-single restorations only, level 2D0530200D0530201D0530210D0530211Endodontic Treatment, Endodontic Treatment procedures, level 2D0631200D0631201D0631210D0631211Endodontic Treatment, Endodontic therapy on permanent teeth, level 1D0633100D0633101D0633110D0633111Endodontic Treatment, Endodontic therapy on permanent teeth, level 2D0633200D0633201D0633210D0633211Endodontic Treatment, Apicoectomy/Periradicular services, level 2D0634200D0634201D0634210D0634211Periodontal Treatment, Periodontal Treatment procedures, level 1D0735100D0735101D0735110D0735111Periodontal Treatment, Surgical services (Including usual postoperative care), level 1D0736100D0736101D0736110D0736111Periodontal Treatment, Surgical services (Including usual postoperative care), level 2D0736200D0736201D0736210D0736211Prosthodontics, Prosthodontics (Removable), level 1D0837100D0837101D0837110D0837111Prosthodontics, Prosthodontics (Removable), level 2D0837200D0837201D0837210D0837211Prosthodontics, Fixed partial denture retainers-crown, level 2D0838200D0838201D0838210D0838211Prosthodontics, Other fixed partial denture service, level 2D0841200D0841201D0841210D0841211Implant services, Implant services procedures, level 2D0943200D0943201D0943210D0943211Orthodontic treatment, Other orthodontic service, level 1D1049100D1049101D1049110D1049111Oral health problems, Other and unspecified management of oral health problems procedures, level 1D1251100D1251101D1251110D1251111Two procedures in one visit, M and M, complexity level 3 and level 3P2200100P2200101P2200110P2200111Two procedures in one visit, D and D, complexity level 2 and level 2P2020400P2020401P2020410P2020411Two procedures in one visit, D and D, complexity level 2 and level 1P2020500P2020501P2020510P2020511Two procedures in one visit, D and D, complexity level 1 and level 1P2020600P2020601P2020610P2020611Two procedures in one visit, M and D, complexity level 3 and level 2P2110200P2110201P2110210P2110211Two procedures in one visit, M and D, complexity level 2 and level 2P2110500P2110501P2110510P2110511Two procedures in one visit, M and D, complexity level 2 and level 1P2110600P2110601P2110610P2110611Two procedures in one visit, M and D, complexity level 1 and level 2P2110800P2110801P2110810P2110811Two procedures in one visit, M and D, complexity level 1 and level 1P2110900P2110901P2110910P2110911Two procedures in one visit, M and M, complexity level 3 and level 3P2200100P2200101P2200110P2200111Two procedures in one visit, M and M, complexity level 3 and level 2P2200200P2200201P2200210P2200211Two procedures in one visit, M and M, complexity level 3 and level 1P2200300P2200301P2200310P2200311Two procedures in one visit, M and M, complexity level 2 and level 2P2200400P2200401P2200410P2200411Two procedures in one visit, M and M, complexity level 2 and level 1P2200500P2200501P2200510P2200511Two procedures in one visit, M and M, complexity level 1 and level 1P2200600P2200601P2200610P2200611Three procedures in one visit, D, D, and D, complexity level 2 and level 2 and level 1P3030800P3030801P3030810P3030811Three procedures in one visit, D, D, and D, complexity level 2 and level 1 and level 1P3030900P3030901P3030910P3030911Three procedures in one visit, D, D, and D, complexity level 1 and level 1 and level 1P3031000P3031001P3031010P3031011Three procedures in one visit, M, D, and D, complexity level 2 and level 2 and level 2P3121000P3121001P3121010P3121011Three procedures in one visit, M, D, and D, complexity level 2 and level 1 and level 1P3121200P3121201P3121210P3121211Three procedures in one visit, M, D, and D, complexity level 1 and level 2 and level 1P3121700P3121701P3121710P3121711Three procedures in one visit, M, D, and D, complexity level 1 and level 1 and level 1P3121800P3121801P3121810P3121811Three procedures in one visit, M, M, and D, complexity level 2 and level 1 and level 1P3211500P3211501P3211510P3211511Three procedures in one visit, M, M, and D, complexity level 1 and level 1 and level 1P3211800P3211801P3211810P3211811Three procedures in one visit, M, M, and M, complexity level 3 and level 2 and level 2P3300400P3300401P3300410P3300411Three procedures in one visit, M, M, and M, complexity level 3 and level 2 and level 1P3300500P3300501P3300510P3300511Three procedures in one visit, M, M, and M, complexity level 3 and level 1 and level 1P3300600P3300601P3300610P3300611Three procedures in one visit, M, M, and M, complexity level 2 and level 2 and level 1P3300800P3300801P3300810P3300811Three procedures in one visit, M, M, and M, complexity level 2 and level 1 and level 1P3300900P3300901P3300910P3300911Three procedures in one visit, M, M, and M, complexity level 1 and level 1 and level 1P3301000P3301001P3301010P3301011Four procedures in one visit, D, D, D, and D, complexity level 2 and level 2 and level 1 and level 1P4041300P4041301P4041310P4041311Four procedures in one visit, D, D, D, and D, complexity level 2 and level 1 and level 1 and level 1P4041400P4041401P4041410P4041411Four procedures in one visit, D, D, D, and D, complexity level 1 and level 1 and level 1 and level 1P4041500P4041501P4041510P4041511Four procedures in one visit, M, D, D, and D, complexity level 2 and level 1 and level 1 and level 1P4132000P4132001P4132010P4132011Four procedures in one visit, M, D, D, and D, complexity level 1 and level 2 and level 1 and level 1P4132900P4132901P4132910P4132911Four procedures in one visit, M, D, D, and D, complexity level 1 and level 1 and level 1 and level 1P4133000P4133001P4133010P4133011Four procedures in one visit, M, M, D, and D, complexity level 2 and level 1 and level 1 and level 1P4223000P4223001P4223010P4223011Four procedures in one visit, M, M, D, and D, complexity level 1 and level 1 and level 1 and level 1P4223600P4223601P4223610P4223611M = oral and maxillofacial surgery (OMFS), D = tooth and periodontium, P = multiple procedures in one visit, GA = general anesthesia, CC= complication and comorbidity.The RIVs relative to the outpatient groups for P, D, and M were 27, 87, and 65 %, respectively, while the inpatient groups’ RIVs for P, D, and M were 16, 0 (number of cases less than five) and 22 %, respectively. The results showed that 100 % of the OHCS classifications had a higher RIV (RIV greater than 0) on cost (Table4). Both the CV and RIV analysis demonstrated the superior performance of the grouper software.The lowest RWs in the outpatient groups for P, D, and M were 0.51 (P3121800), 0.14 (D0222100), and 0.30 (M1999101), respectively, while the highest RWs of the outpatient groups were 3.59 (P3121000), 21.33 (D0843200), and 7.88 (M3002200), respectively. The lowest RWs relative to the inpatient groups for P, D, and M were 0.13 (P2200600), 0 (the number of cases was less than five) and 0.02 (M1999100), respectively, while the inpatients’ highest RWs were 2.03 (P3300510), 0 (the number of cases was less than five), and 3.46 (M3202210), respectively (Table4, Annex Table 5). A high RW indicated a higher case complexity and more resources required for treatment than for low RW cases. Moreover, RW was the most important result of the calibration because it was the determinant for the payment to healthcare providers.


### 3.5. Payment

This study calculated the base rate characteristics by splitting cases into three main treatment groups consisting of P, D, and M and two patient groups consisting of inpatient and outpatient. The results showed that the highest base rate among the three main treatment groups relative to the outpatient groups and the inpatient groups were D and P, respectively.


## 3.1. Coding

Part I (Steps One and Two)
The ICD-10-TM, consisting of 813 diagnoses and 1,090 procedures related to OHCS, were retrieved and mapped to ICD-10 and ICD-9-CM, respectively.Part II
The electronic data of individual patients from three selected tertiary hospitals were checked by an inclusion list of PDx and Proc. There were 16,165 (84.64%) cases out of 19,098 initial cases (cases with incomplete data were eliminated) that met the inclusion criteria. The number of inpatient and outpatient cases were 2,709 (16.8%) and 13,456 (83.2%), respectively. The demographic details, clinical information and health insurance showed that the majority of the patients were female (8,723 cases; 54.0%), non-GA (13,911 cases; 86.05%), non-CC (15,708 cases; 97.17%), and CSMBS (6,368 cases; 39.4%).


## 3.2. Classification

The new OHCS casemix classification model (Grouper) consisted of two major procedure categories, M and D, 62 procedure clusters (Table1), 165 subgroups of procedure clusters (Table 2), and 1,624 OHCS classifications according to the treatment procedures (Annex Table 5). Each OHCS classification described a cluster of patients with related diagnoses, requiring a similar examination and incurring similar treatment costs.  There were 16,165 patients who were grouped into OHCS classifications by the grouper software. After the grouping process, only 307 OHCS classifications were achieved to cover these procedure codes. This result was likely limited by the OHCS data, as the amount available in this pilot study was not sufficient to support the OHCS grouper.


## 3.3. Costs

For predicting costs, regression analysis was employed. Table3 presents the determination of the cost of P, D, and M. Because cost did not present a normal distribution, a normal logarithmic transformation was undertaken. The predicted cost of P, D, and M had R2values of 0.892, 0.132, and 0.122, respectively, and the probability of the F-test statistic was 0.000. The results showed that the GA, CC, number of procedures in one visit, Proc (divided by the level of complexity), and LOS were associated with the costs of P, D, and M.Table 3
Multiple regressions of the cost of multiple procedures (P), the cost of OMFS (M), and the cost of tooth and periodontium (D).
Cost of multiple procedures (P)Cost of OMFS (M)Cost of tooth and periodontium (D)95% CI95% CI95% CIOdds-ratioLower-upperP-valueOdds-ratioLower-upperP-valueOdds-ratioLower-upperP-valueGenderMale (reference)Female0.970.89–1.13.9731.141.02–1.19.0090.950.88–1.03.243Age0–22 (reference)23–401.040.89–1.22.6711.561.39–1.74<.0011.020.91–1.15.63341–540.880.75–1.03.1211.171.05–1.31.040.820.73–0.92.00154 +0.850.73–0.99.0391.171.15–1.30.030.790.71–0.88<.001GANon-GA (reference)GA295.78162.41–538.67<.0011.571.49–1.66<.0012386.74891.84–6387.39<.001Number of procedures1 (reference)29.558.72–12.45.0331.021.01–1.03<.0011.021.01–1.02<.00132.721.35–4.56<.0011.211.16–1.28<.0011.191.14–1.23<.00148.686.78–11.34<.0011.161.12–1.20<.0011.161.13–1.27<.001CCNon-CC (reference)CC3.252.31–4.57<.0011.171.10–1.31<.00115.7611.25–21.96<.001Complexity1 (reference)2-33.812.31–4.57<.0011.911.89–1.92<.0011.911.89–1.92<.001LOSLE21 (reference)GE220.150.06–0.33<.0011.531.38–1.73<.0010.020.05–0.08<.001Adjusted cost of multiple procedures (P)R2=0.892, cost of OMFS (M) R2=0.122, and cost of tooth and periodontium (D) R2=0.132GA = general anesthesia, Number of procedures = total procedures in one visit, CC = complication and comorbidityComplexity = level of complexity (1 = simple procedure, 2 = complex procedure, 3 = multidisciplinary or complicated procedure)LOS = length of stay (LE21 = less than and equal to 21, GE22 = more than 21).


## 3.4. Calibration

To ensure that the OHCS classifications reflected resource homogeneity within groups and heterogeneity between groups, the CV and RIV, respectively, were used for analysis.The lowest CVs relative to the outpatient groups for P, D, and M were 0.02 (P2110200), 0.01 (D0843200), and 0.19 (M4004100), respectively, while the highest CVs relative to these groups for P, D, and M were 0.87 (P2020500), 0.99 (D0736200), and 0.83 (M4310101), respectively. The lowest CVs relative to the inpatient groups for P, D, and M were 0.31 (P2200511), 0 (the number of cases was less than five), and 0.22 (M4004100), respectively, while the inpatients’ highest CVs for P, D, and M were 0.98 (P2200410), 0 (the number of cases was less than five), and 0.99 (M3002110), respectively. Moreover, all OHCS classifications had a CV on cost of less than one (Table4, Annex Table 5).Table 4
Summary of the statistical analysis of the coefficient of variation (CV), reduction in variance (RIV), and relative weight (RW).
OHCSN (cases)CVRIVRWInpatientOutpatientInpatientOutpatientInpatientOutpatientInpatientOutpatientP3657,8320.31–0.980.02–0.8716%27%0.13–2.030.51–3.59D32,619N/A0.01–0.99N/A87%N/A0.14–21.33M2,3413,0050.22–0.990.19–0.8322%65%0.02–3.460.30–7.88P = multiple procedures in one visit, D = tooth and periodontium, M = oral and maxillofacial surgery (OMFS)CV = coefficient of variation, RIV = reduction in variance, RW = relative weight, N/A = not applicable.Table 5
Demonstrates examples of the oral healthcare service (OHCS) groupers.
Description of oral healthcare service (OHCS) classificationsWithout GAWithout GAWith GAWith GAwithout CCwith CCwithout CCwith CCSkull, Operative procedures, level 3M0202300M0202301M0202310M0202311Face, Operative procedures, level 1M0702100M0702101M0702110M0702111Maxilla, Operative procedures, level 1M0802100M0802101M0802110M0802111Maxilla, Operative procedures, level 2M0802200M0802201M0802210M0802211Maxilla, Operative procedures, level 3M0802300M0802301M0802310M0802311Mandible, Diagnostic procedures and nonoperative procedures, level 1M0901100M0901101M0901110M0901111Mandible, Diagnostic procedures and nonoperative procedures, level 2M0901200M0901201M0901210M0901211Mandible, Diagnostic procedures and nonoperative procedures, level 3M0901300M0901301M0901310M0901311Mandible, Operative procedures, level 1M0902100M0902101M0902110M0902111Mandible, Operative procedures, level 2M0902200M0902201M0902210M0902211Mandible, Operative procedures, level 3M0902300M0902301M0902310M0902311Facial bone, Operative procedures, level 2M1002200M1002201M1002210M1002211Facial bone, Operative procedures, level 3M1002300M1002301M1002310M1002311Nose, Repair or reconstruction, level 1M1906100M1906101M1906110M1906111Nose, Other procedures and operations, level 1M1999100M1999101M1999110M1999111Nasal cavity, Removal and replacement of nasal packing and Control of epistaxis level 1M2009100M2009101M2009110M2009111Nasal cavity, Other procedures and operations, level 1M2099100M2099101M2099110M2099111Nasal cavity, Other procedures and operations, level 2M2099200M2099201M2099210M2099211Nasal septum, Repair or reconstruction, level 3M2206300M2206301M2206310M2206311Frontal nasal sinuses, Repair or reconstruction, level 1M2306100M2306101M2306110M2306111Frontal nasal sinuses, Repair or reconstruction, level 2M2306200M2306201M2306210M2306211Frontal nasal sinuses, Repair or reconstruction, level 3M2306300M2306301M2306310M2306311Paranasal sinuses, Incision and Excision or destruction, level 1M2504100M2504101M2504110M2504111Parotid salivary gland, Incision and Excision or destruction, level 1M2604100M2604101M2604110M2604111Parotid salivary gland, Incision and Excision or destruction, level 2M2604200M2604201M2604210M2604211Salivary gland and duct, Incision and Excision or destruction, level 1M2804100M2804101M2804110M2804111Salivary gland and duct, Incision and Excision or destruction, level 2M2804200M2804201M2804210M2804211Neck, Diagnostic procedures and nonoperative procedures, level 1M2901100M2901101M2901110M2901111Neck, Diagnostic procedures and nonoperative procedures, level 2M2901200M2901201M2901210M2901211Neck skin, Diagnostic procedures and nonoperative procedures, level 1M3001100M3001101M3001110M3001111Neck skin, Operative procedures, level 1M3002100M3002101M3002110M3002111Neck skin, Operative procedures, level 2M3002200M3002201M3002210M3002211Neck skin, Operative procedures, level 3M3002300M3002301M3002310M3002311Carotid artery, Operative procedures, level 1M3202100M3202101M3202110M3202111Carotid artery, Operative procedures, level 2M3202200M3202201M3202210M3202211Cervical lymph nodes, Diagnostic procedures and nonoperative procedures, level 1M3301100M3301101M3301110M3301111Cervical lymph nodes, Diagnostic procedures and nonoperative procedures, level 2M3301200M3301201M3301210M3301211Thyroglossal reminant, Incision and Excision or destruction, level 1M3504100M3504101M3504110M3504111Thyroglossal reminant, Incision and Excision or destruction, level 2M3504200M3504201M3504210M3504211Lip, Incision and Excision or destruction, level 1M3604100M3604101M3604110M3604111Lip, Incision and Excision or destruction, level 2M3604200M3604201M3604210M3604211Lip, Repair or reconstruction, level 1M3606100M3606101M3606110M3606111Lip, Repair or reconstruction, level 2M3606200M3606201M3606210M3606211Floor of mouth, Incision and Excision or destruction, level 1M3804100M3804101M3804110M3804111Mouth, Diagnostic procedures and nonoperative procedures, level 1M3901100M3901101M3901110M3901111Mouth, Miscellaneous procedures, level 1M3903100M3903101M3903110M3903111Mouth, Incision and Excision or destruction, level 1M3904100M3904101M3904110M3904111Mouth, Incision and Excision or destruction, level 2M3904200M3904201M3904210M3904211Mouth, Repair or reconstruction, level 1M3906100M3906101M3906110M3906111Tongue, Incision and Excision or destruction, level 1M4004100M4004101M4004110M4004111Deciduous teeth, General procedures, level 1M4210100M4210101M4210110M4210111Permanent teeth, General procedures, level 1M4310100M4310101M4310110M4310111Permanent teeth, General procedures, level 2M4310200M4310201M4310210M4310211Soft palate, Repair or reconstruction, level 1M4606100M4606101M4606110M4606111Soft palate, Repair or reconstruction, level 2M4606200M4606201M4606210M4606211Uvula, Repair or reconstruction, level 1M4706100M4706101M4706110M4706111Uvula, Repair or reconstruction, level 2M4706200M4706201M4706210M4706211Uvula, Other procedures and operations on oral cavity, level 1M4799100M4799101M4799110M4799111Uvula, Other procedures and operations on oral cavity, level 2M4799200M4799201M4799210M4799211Uvula, Other procedures and operations on oral cavity, level 3M4799300M4799301M4799310M4799311Oral examination, Oral  examination procedures, level 1D0121100D0121101D0121110D0121111Radiographs/Diagnostic imaging, Intraoral film, level 1D0222100D0222101D0222110D0222111Radiographs/Diagnostic imaging, Extraoral film, level 1D0223100D0223101D0223110D0223111Preventive Dentistry, Preventive Dentistry procedures, level 1D0324100D0324101D0324110D0324111Tooth Restoration, Amalgam restorations (including polishing), level 1D0526100D0526101D0526110D0526111Tooth Restoration, Resin-based composite restorations, level 1D0527100D0527101D0527110D0527111Tooth Restoration, Resin-based composite restorations, level 2D0527200D0527201D0527210D0527211Tooth Restoration, Crown-single restorations only, level 1D0530100D0530101D0530110D0530111Tooth Restoration, Crown-single restorations only, level 2D0530200D0530201D0530210D0530211Endodontic Treatment, Endodontic Treatment procedures, level 2D0631200D0631201D0631210D0631211Endodontic Treatment, Endodontic therapy on permanent teeth, level 1D0633100D0633101D0633110D0633111Endodontic Treatment, Endodontic therapy on permanent teeth, level 2D0633200D0633201D0633210D0633211Endodontic Treatment, Apicoectomy/Periradicular services, level 2D0634200D0634201D0634210D0634211Periodontal Treatment, Periodontal Treatment procedures, level 1D0735100D0735101D0735110D0735111Periodontal Treatment, Surgical services (Including usual postoperative care), level 1D0736100D0736101D0736110D0736111Periodontal Treatment, Surgical services (Including usual postoperative care), level 2D0736200D0736201D0736210D0736211Prosthodontics, Prosthodontics (Removable), level 1D0837100D0837101D0837110D0837111Prosthodontics, Prosthodontics (Removable), level 2D0837200D0837201D0837210D0837211Prosthodontics, Fixed partial denture retainers-crown, level 2D0838200D0838201D0838210D0838211Prosthodontics, Other fixed partial denture service, level 2D0841200D0841201D0841210D0841211Implant services, Implant services procedures, level 2D0943200D0943201D0943210D0943211Orthodontic treatment, Other orthodontic service, level 1D1049100D1049101D1049110D1049111Oral health problems, Other and unspecified management of oral health problems procedures, level 1D1251100D1251101D1251110D1251111Two procedures in one visit, M and M, complexity level 3 and level 3P2200100P2200101P2200110P2200111Two procedures in one visit, D and D, complexity level 2 and level 2P2020400P2020401P2020410P2020411Two procedures in one visit, D and D, complexity level 2 and level 1P2020500P2020501P2020510P2020511Two procedures in one visit, D and D, complexity level 1 and level 1P2020600P2020601P2020610P2020611Two procedures in one visit, M and D, complexity level 3 and level 2P2110200P2110201P2110210P2110211Two procedures in one visit, M and D, complexity level 2 and level 2P2110500P2110501P2110510P2110511Two procedures in one visit, M and D, complexity level 2 and level 1P2110600P2110601P2110610P2110611Two procedures in one visit, M and D, complexity level 1 and level 2P2110800P2110801P2110810P2110811Two procedures in one visit, M and D, complexity level 1 and level 1P2110900P2110901P2110910P2110911Two procedures in one visit, M and M, complexity level 3 and level 3P2200100P2200101P2200110P2200111Two procedures in one visit, M and M, complexity level 3 and level 2P2200200P2200201P2200210P2200211Two procedures in one visit, M and M, complexity level 3 and level 1P2200300P2200301P2200310P2200311Two procedures in one visit, M and M, complexity level 2 and level 2P2200400P2200401P2200410P2200411Two procedures in one visit, M and M, complexity level 2 and level 1P2200500P2200501P2200510P2200511Two procedures in one visit, M and M, complexity level 1 and level 1P2200600P2200601P2200610P2200611Three procedures in one visit, D, D, and D, complexity level 2 and level 2 and level 1P3030800P3030801P3030810P3030811Three procedures in one visit, D, D, and D, complexity level 2 and level 1 and level 1P3030900P3030901P3030910P3030911Three procedures in one visit, D, D, and D, complexity level 1 and level 1 and level 1P3031000P3031001P3031010P3031011Three procedures in one visit, M, D, and D, complexity level 2 and level 2 and level 2P3121000P3121001P3121010P3121011Three procedures in one visit, M, D, and D, complexity level 2 and level 1 and level 1P3121200P3121201P3121210P3121211Three procedures in one visit, M, D, and D, complexity level 1 and level 2 and level 1P3121700P3121701P3121710P3121711Three procedures in one visit, M, D, and D, complexity level 1 and level 1 and level 1P3121800P3121801P3121810P3121811Three procedures in one visit, M, M, and D, complexity level 2 and level 1 and level 1P3211500P3211501P3211510P3211511Three procedures in one visit, M, M, and D, complexity level 1 and level 1 and level 1P3211800P3211801P3211810P3211811Three procedures in one visit, M, M, and M, complexity level 3 and level 2 and level 2P3300400P3300401P3300410P3300411Three procedures in one visit, M, M, and M, complexity level 3 and level 2 and level 1P3300500P3300501P3300510P3300511Three procedures in one visit, M, M, and M, complexity level 3 and level 1 and level 1P3300600P3300601P3300610P3300611Three procedures in one visit, M, M, and M, complexity level 2 and level 2 and level 1P3300800P3300801P3300810P3300811Three procedures in one visit, M, M, and M, complexity level 2 and level 1 and level 1P3300900P3300901P3300910P3300911Three procedures in one visit, M, M, and M, complexity level 1 and level 1 and level 1P3301000P3301001P3301010P3301011Four procedures in one visit, D, D, D, and D, complexity level 2 and level 2 and level 1 and level 1P4041300P4041301P4041310P4041311Four procedures in one visit, D, D, D, and D, complexity level 2 and level 1 and level 1 and level 1P4041400P4041401P4041410P4041411Four procedures in one visit, D, D, D, and D, complexity level 1 and level 1 and level 1 and level 1P4041500P4041501P4041510P4041511Four procedures in one visit, M, D, D, and D, complexity level 2 and level 1 and level 1 and level 1P4132000P4132001P4132010P4132011Four procedures in one visit, M, D, D, and D, complexity level 1 and level 2 and level 1 and level 1P4132900P4132901P4132910P4132911Four procedures in one visit, M, D, D, and D, complexity level 1 and level 1 and level 1 and level 1P4133000P4133001P4133010P4133011Four procedures in one visit, M, M, D, and D, complexity level 2 and level 1 and level 1 and level 1P4223000P4223001P4223010P4223011Four procedures in one visit, M, M, D, and D, complexity level 1 and level 1 and level 1 and level 1P4223600P4223601P4223610P4223611M = oral and maxillofacial surgery (OMFS), D = tooth and periodontium, P = multiple procedures in one visit, GA = general anesthesia, CC= complication and comorbidity.The RIVs relative to the outpatient groups for P, D, and M were 27, 87, and 65 %, respectively, while the inpatient groups’ RIVs for P, D, and M were 16, 0 (number of cases less than five) and 22 %, respectively. The results showed that 100 % of the OHCS classifications had a higher RIV (RIV greater than 0) on cost (Table4). Both the CV and RIV analysis demonstrated the superior performance of the grouper software.The lowest RWs in the outpatient groups for P, D, and M were 0.51 (P3121800), 0.14 (D0222100), and 0.30 (M1999101), respectively, while the highest RWs of the outpatient groups were 3.59 (P3121000), 21.33 (D0843200), and 7.88 (M3002200), respectively. The lowest RWs relative to the inpatient groups for P, D, and M were 0.13 (P2200600), 0 (the number of cases was less than five) and 0.02 (M1999100), respectively, while the inpatients’ highest RWs were 2.03 (P3300510), 0 (the number of cases was less than five), and 3.46 (M3202210), respectively (Table4, Annex Table 5). A high RW indicated a higher case complexity and more resources required for treatment than for low RW cases. Moreover, RW was the most important result of the calibration because it was the determinant for the payment to healthcare providers.


## 3.5. Payment

This study calculated the base rate characteristics by splitting cases into three main treatment groups consisting of P, D, and M and two patient groups consisting of inpatient and outpatient. The results showed that the highest base rate among the three main treatment groups relative to the outpatient groups and the inpatient groups were D and P, respectively.


## 4. Discussion

This is a study of the preliminary development of a new casemix classification system related to ICD-10-TM in Thai OHCS. The results indicated that the new casemix system was reliable and could possibly be utilized as a first version. However, many points need to be discussed.


### 4.1. Coding

In Thailand, the healthcare system has implemented ICD-10 for Dx and ICD-9-CM for Proc for many years. Recently, ICD-10-TM has been implemented to provide more details in the OHCS coding by modifying it with International Classification of Disease to Dentistry and Stomatology (ICD-DA) for Dx and CDT for Proc. The most recent modification of the codes was finished in 2003 [23, 24].  Thus, the ICD-10-TM provides an advantage in terms of accuracy and comprehensive coverage for Dx and Proc. It is unique, but similar to the CDT and matched with Proc one by one while ICD-9-CM has many Proc for each code. These differences indicate that ICD-10-TM was suitable, although challenging, for this study.


### 4.2. Classification

The development of the new casemix classification for OHCS concentrated on practical application of the IR-DRG that was instituted by 3M Health Information System. IR-DRG was able to classify inpatient and outpatient status and was also useful for appraising the potential for replacement on both short stay and ambulatory treatments [31]. Taking this fact into consideration, the new casemix classification was classified by the nature of the patients’ procedures rather than by their diagnoses. This classification system was developed to allow the translation of dental procedures into eight-digit codes using various variables to obtain a homogenous resource group.


### 4.3. Costs

There are a variety of methods for estimating the provider’s cost. However, each method has limitations.  The cost of OHCS varies depending upon several factors: the characteristics of the OHCS, the scope and complexity of the treatment, the specialty and experience of physician, the high investment cost, and the location of the practice. It was difficult to measure the total submitted charges for cases in each OHCS classification. Therefore, the cost in this study was calculated based on the use of the patient payment to estimate the provider's cost.It was expected that this method would be suitable to calibrate the OHCS classification in this study. However, a future study using a resource-based relative value scale (RBRVS) would be recommended. Because RBRVS is a schema that is used to calculate what medical providers should be paid, it assigns a relative value unit (RVUs) to each physician service that is based on three items: the physician, the practice expense, and the malpractice expense. This schema is currently used by Medicare in the United States and by nearly all Health Maintenance Organizations (HMOs) [32–34]. In 2009, Relative Value Studies Incorporated (RVSI) of Denver, Colorado developed Relative Values for Dentists (RVD), a RBRVS for dentistry that is currently indexed to the Current Dental Terminology (CDT) and supplemented by additional coding as recommended by practicing dentists [35].


### 4.4. Calibration and Payment

Because of the wide range of costs among the set of P, D, M, inpatient, and outpatient categories, the weight should reflect the relative cost of providing care and the health resources required in each DRG. A CV of less than one and a higher RIV would be expected in the new OHCS classification. Thus, the RIV, RW, and base rate characteristics were split into three main treatment groups consisting of P, D, and M and two patient groups consisting of inpatient and outpatient for the following reasons.(i)
The higher RIV reflects the better performance of the grouping. However, P had the lowest RIV in both inpatient and outpatient groups because P included multiple procedures in one visit, and in some cases P had M and D in one visit. P also had more data and variation than did the other groups. The RIV of M of the inpatient group was lower than the RIV of M of the outpatient group because all inpatient procedures were major surgeries with GA, complex, and costly procedures. D had the highest RIV in the outpatient group because all procedures in the outpatient group were minor surgeries, tooth and periodontium treatment, without GA.(ii)
The procedures of each group were different according to the anatomy group, root operation, and total procedures in one visit.(iii)
Elementary procedures in the OHCS were wildly different in each group. The OHCS was mostly focused on handiwork. OHCS was intensively skilled, time-consuming labor with a high investment cost for the equipment, instruments, and materials [36].Taken together, this new OHCS grouper has been potentially implemented in Thailand. However, in some countries that use ICD-10 for Dx, ICD-9-CM for Proc and DRG for budget allocation, this information of the mapping process could be used as a guideline to further develop their own systems. Moreover, the benefits of the DRG grouper for OHCS could be used for expenditure estimation, resource allocation, payment, and oral healthcare finance focus.


### 4.5. Limitation

The problems related to the implementation of a new casemix classification for OHCS are elaborated as follows.(i)
Although computerized information systems are widely used in Thailand, only a few hospitals provided good clinical data that were ready to use [11]. This was an important issue for OHCS information because ICD-10 and ICD-9-CM were not commonly used for recording with the same standardization. This problem was likely due to the limited data from OHCS in Thailand, which could not support an OHCS grouper.(ii)
The diagnoses and procedures of the OHCS coding system are scattered throughout the ICD-10 and ICD-9-CM, making them difficult to find and use. Moreover, currently OHCS codings are not being used effectively in dentistry.(iii)
The OHCS patient data from this study did not involve patients from university hospitals because the patients in university hospitals had more heterogeneity in their diagnoses and services than did other hospitals. In addition, OHCS classification subgroups may be needed to more precisely describe the resource consumption in the university hospital setting.(iv)
There were 1,624 OHCS classifications. In this pilot study, the data were limited and were not sufficient to support the OHCS grouper. A large number of OHCS classifications might be difficult to handle as a good payment tool. In the future, the OHCS classification should decrease the number of groups to provide more efficiency and effectiveness in payment.(v)
OHCS cost weights were calculated using only cost data from some areas that might not be applicable to all hospitals in Thailand. This indicated that an expanded number of cases and data from additional hospitals would give a more exact cost weight.


## 4.1. Coding

In Thailand, the healthcare system has implemented ICD-10 for Dx and ICD-9-CM for Proc for many years. Recently, ICD-10-TM has been implemented to provide more details in the OHCS coding by modifying it with International Classification of Disease to Dentistry and Stomatology (ICD-DA) for Dx and CDT for Proc. The most recent modification of the codes was finished in 2003 [23, 24].  Thus, the ICD-10-TM provides an advantage in terms of accuracy and comprehensive coverage for Dx and Proc. It is unique, but similar to the CDT and matched with Proc one by one while ICD-9-CM has many Proc for each code. These differences indicate that ICD-10-TM was suitable, although challenging, for this study.


## 4.2. Classification

The development of the new casemix classification for OHCS concentrated on practical application of the IR-DRG that was instituted by 3M Health Information System. IR-DRG was able to classify inpatient and outpatient status and was also useful for appraising the potential for replacement on both short stay and ambulatory treatments [31]. Taking this fact into consideration, the new casemix classification was classified by the nature of the patients’ procedures rather than by their diagnoses. This classification system was developed to allow the translation of dental procedures into eight-digit codes using various variables to obtain a homogenous resource group.


## 4.3. Costs

There are a variety of methods for estimating the provider’s cost. However, each method has limitations.  The cost of OHCS varies depending upon several factors: the characteristics of the OHCS, the scope and complexity of the treatment, the specialty and experience of physician, the high investment cost, and the location of the practice. It was difficult to measure the total submitted charges for cases in each OHCS classification. Therefore, the cost in this study was calculated based on the use of the patient payment to estimate the provider's cost.It was expected that this method would be suitable to calibrate the OHCS classification in this study. However, a future study using a resource-based relative value scale (RBRVS) would be recommended. Because RBRVS is a schema that is used to calculate what medical providers should be paid, it assigns a relative value unit (RVUs) to each physician service that is based on three items: the physician, the practice expense, and the malpractice expense. This schema is currently used by Medicare in the United States and by nearly all Health Maintenance Organizations (HMOs) [32–34]. In 2009, Relative Value Studies Incorporated (RVSI) of Denver, Colorado developed Relative Values for Dentists (RVD), a RBRVS for dentistry that is currently indexed to the Current Dental Terminology (CDT) and supplemented by additional coding as recommended by practicing dentists [35].


## 4.4. Calibration and Payment

Because of the wide range of costs among the set of P, D, M, inpatient, and outpatient categories, the weight should reflect the relative cost of providing care and the health resources required in each DRG. A CV of less than one and a higher RIV would be expected in the new OHCS classification. Thus, the RIV, RW, and base rate characteristics were split into three main treatment groups consisting of P, D, and M and two patient groups consisting of inpatient and outpatient for the following reasons.(i)
The higher RIV reflects the better performance of the grouping. However, P had the lowest RIV in both inpatient and outpatient groups because P included multiple procedures in one visit, and in some cases P had M and D in one visit. P also had more data and variation than did the other groups. The RIV of M of the inpatient group was lower than the RIV of M of the outpatient group because all inpatient procedures were major surgeries with GA, complex, and costly procedures. D had the highest RIV in the outpatient group because all procedures in the outpatient group were minor surgeries, tooth and periodontium treatment, without GA.(ii)
The procedures of each group were different according to the anatomy group, root operation, and total procedures in one visit.(iii)
Elementary procedures in the OHCS were wildly different in each group. The OHCS was mostly focused on handiwork. OHCS was intensively skilled, time-consuming labor with a high investment cost for the equipment, instruments, and materials [36].Taken together, this new OHCS grouper has been potentially implemented in Thailand. However, in some countries that use ICD-10 for Dx, ICD-9-CM for Proc and DRG for budget allocation, this information of the mapping process could be used as a guideline to further develop their own systems. Moreover, the benefits of the DRG grouper for OHCS could be used for expenditure estimation, resource allocation, payment, and oral healthcare finance focus.


## 4.5. Limitation

The problems related to the implementation of a new casemix classification for OHCS are elaborated as follows.(i)
Although computerized information systems are widely used in Thailand, only a few hospitals provided good clinical data that were ready to use [11]. This was an important issue for OHCS information because ICD-10 and ICD-9-CM were not commonly used for recording with the same standardization. This problem was likely due to the limited data from OHCS in Thailand, which could not support an OHCS grouper.(ii)
The diagnoses and procedures of the OHCS coding system are scattered throughout the ICD-10 and ICD-9-CM, making them difficult to find and use. Moreover, currently OHCS codings are not being used effectively in dentistry.(iii)
The OHCS patient data from this study did not involve patients from university hospitals because the patients in university hospitals had more heterogeneity in their diagnoses and services than did other hospitals. In addition, OHCS classification subgroups may be needed to more precisely describe the resource consumption in the university hospital setting.(iv)
There were 1,624 OHCS classifications. In this pilot study, the data were limited and were not sufficient to support the OHCS grouper. A large number of OHCS classifications might be difficult to handle as a good payment tool. In the future, the OHCS classification should decrease the number of groups to provide more efficiency and effectiveness in payment.(v)
OHCS cost weights were calculated using only cost data from some areas that might not be applicable to all hospitals in Thailand. This indicated that an expanded number of cases and data from additional hospitals would give a more exact cost weight.


## 5. Conclusion

This study demonstrated the validity of the new OHCS classification, showing high homogeneity of the cases within each group and heterogeneity of the cases between each group. Furthermore, it could be used to predict and control production costs. Therefore, this OHCS casemix classification has the potential to be used in global decision-making in the future. Moreover, some countries using ICD-10 for diagnoses, ICD-9-CM for procedures, and DRG grouper for budget allocation might be able to apply this mapping process as a guideline to develop their own system, which might benefit from the use of the DRG grouper for expenditure estimation, resource allocation, payment, and healthcare finance focus.



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*Source: 231398-2010-09-20.xml*