Department of Health and Human Services 

OFFICE OF 

INSPECTOR GENERAL 

DRG 79 VALIDATION STUDY UPDATE: 

RESPIRATORY INFECTIONS AND 

INFLAMMATIONS 

‘e . 

FEBRUARY 1993 
OFFICE OF INSPECTOR GENERAL 

The mission of the Office of Inspector General (OIG), as mandated by Public Law 95-

452, as amended, is to protect the integrity of the Department of Health and Human 

Services (HHS) programs as well as the health and welfare of beneficiaries served by 

those programs. This statuto~ mission is carried out through a nationwide network of 

audits, investigations, and inspections conducted by three OIG operating components: 

the Office of Audit Services, the Office of Investigations, and the Office of Evaluations 

and Inspections. The OIG also informs the Secretary of HHS program and 

management problems and recommends courses to correct them. 

OFFICE OF AUDIT SERVICES 

The OIG’S Office of Audit Services (OAS) provides all auditing sewices for HHS, 

either by conducting audits with its own audit resources or by overseeing audit work 

done by others. Audits examine the performance of HHS programs and/or its 

grantees and contractors in carrying out their respective responsibilities and are 

intended to provide independent assessments of HHS programs and operations in 

order to reduce waste, abuse, and mismanagement and to promote economy and 

efficiency throughout the Department. 

OFFICE OF 

The OIG’S Office of Investigations (01) 

INVESTIGATIONS 

conducts criminal, civil, and administrative 

investigations of allegations ‘of wrongdoing in HHS programs or to HHS beneficiaries 

and of unjust enrichment by providers. The investigative efforts of 01 lead to criminal 

convictions, administrative sanctions, or civil money penalties. The 01 also oversees 

state Medicaid fraud control units which investigate and prosecute fraud and patient 

abuse in the Medicaid program. 

OFFICE OF EVALUATION AND INSPECITONS 

The OIG’S Office of Evaluation and Inspections (OEI) conducts short-term 

management and program evaluations (called inspections) that focus on issues of 

concern to the Department, the Congress, and the public. The findings and 

recommendations contained in these inspection reports generate rapid, accurate, and 

up-to-date information on the efficiency, vulnerability, and effectiveness of 

departmental programs. 

Amy L. Lockwood of BOTEC Analysis Corporation prepared this report with 

direction from Janet W. Knight, BOTEC Project Director, and David C. Hsia, OIG 

Project Officer. Contract information and project participants are listed in Appendix 1 

to this inspection. 
Department of Health and Human Services 

OFFICE OF 

INSPECTOR GENERAL 

DRG 79 VALIDATION STUDY UPDATE: 

RESPIRATORY INFECTIONS AND 

INFLAMMATIONS 

FEBRUARY 1993 OEI-12-89-00193 
EXECUTIVE SUMMARY


PURPOSE 

This inspection reabstracted on a blinded basis, the International Classification of 

Diseases, Ninth Revision, Clinical Modification codes from a sample of Medicare 

discharges billed as diagnosis-related group (DRG) 79: Respiratory infections and 

inflammations. It compared the reabstracted DRG to the hospital-billed DRG for 

reimbursement changes. The sample was nationally representative and covered all of 

1988, the most recent data available. 

This inspection updated a previous Office of Inspector General (OIG) study. For 

1985, the OIG found 18.4 percent errors among 74 reabstractions, improperly overreimbursing hospitals by a projected $28.4 million. This inspection used a parallel 

methodology to make these studies statistically comparable. Statistical tests 

determined whether numeric differences between 1985 results and 1988 results were 

real (statistically significant) or could be attributed to random error. 

FINDINGS 

DRG 79 bihg emr redhced 

Of 123 discharges reabstracted for this inspection, 11 (8.9 percent) were incorrectly 

assigned to DRG 79. This was a statistically-significant improvement over the 18.4 

percent error rate for DRG 79 in 1985. This rate also significantly differs from the 

14.7 percent errors for all discharges in 1988. 

Financial impact of DRG 79 billikg emor not redh.ced @nificantZy 

This inspection projected that discharges incorrectly assigned to DRG 79 overreimbursed hospitals $22.7 million. This result did not significantly differ from the 

$28.4 million over-reimbursement in 1985. The increase in the number of DRG 79 

bills in 1988 offset the decrease in the proportion of errors. 

i 
TABLE OF CONTENTS 

EXECUTIVE suMMARY 

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

FINDINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...4 

S Errors reduced . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

“Most errors over-reimbursed hospitals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

“Hospitals still over-reimbursed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

ENDNOTES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

AGENCY COMMENTS 

APPENDICES 

f% 

B: 

c 

D: 

E. 

F: 

Project participants . 

� .0..0. . . . . . . . .0.,... . . . . . . . .0...00 . ..00.. 

. . . . . . . . ..0..0 . . . . . . . . . . . . . . . . . ...0 . . . . . . . 

ICD-9-CM procedure codes in DRG79 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Sample representativeness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

DRG79billing errors, 1985 and 1988.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

DRG79case-mix index change, 1985 and 1988 . . . . . . . . . . . . . . . . . . . . . . . 

Reasons for DRG79errors, 1985 and 1988 . . . . . . . . . . . . . . . . . . . . . . . . . . 

. 

� 

� 

� � 

.0 

4 

4 

4 

6 

7 

A-1 

B-1 

c-1 

D-1 

E-1 

F-1 
INTRODUCTION 

Background 

Diagnosis-related group (DRG) 79: Respiratory infections and inflammations; 

includes 168 International Classification of Diseases, Ninth Revision, Clinical 

Modification (ICD-9-CM) codes. These ICD-9-CM codes identi~ infectious diseases, 

particularly tuberculin bacillus exposure or tuberculosis infection, as well as anthrax, 

mycobacterial infections, empyema, abscesses, and similar infectious conditions. 

Tuberculosis incidence had decreased with improved standards of living and the 

advent of antibiotics. It has recently become endemic again, primarily in immigrant 

and homeless populations. This resurgence may also affect Medicare beneficiaries. 

DRG 79’s weight increased from 1.7795 in 1985 to 2.0777 in 1988. Since 1985, the 

Health Care Financing Administration (HCFA) altered DRG 79 to eliminate “age 

over 69” as a complication code and created DRGs 474 and 475 for ventilator-assisted 

patients. These changes shifted billings in one quarter of the data collection period 

for this inspection. 

In a previous study, the OIG found that DRG 79 had a disproportionately high 

proportion of billing errors.1 Correct ICD-9-CM coding would have grouped 18.4 

percent of its 74 reabstractions to different DRGs in 1985. These billing errors overreimbursed the hospitals a projected $28.4 million. 

This inspection updated the previous study using 1988 data, the most recent available. 

It used a parallel methodology to make these inspections statistically comparable. 

Methodology 

This inspection randomly selected 123 DRG 79 discharges from 26 hospitals. The 

study population consisted of 102,561 Medicare-reimbursed DRG 79 discharges during 

Calendar Year 1988. The design excluded discharges from specialty institutions such 

as children’s hospitals, tuberculosis units, and psychiatric facilities. It also excluded 

discharges in Maryland and New Jersey, which the PPS still exempted in 1988. Finally, 

it excluded bills for pediatric, obstetric, and psychiatric DRGs (principally drug and 

alcohol rehabilitation performed by a general hospital).2 Unlike its 1985 predecessor, 

it included hospitals established since the advent of the PPS in 1983. 

The OIG requested that hospitals send complete copies of the sampled medical 

records to the OIG’S contractor, Baxter-Health Data Institute (HDI) of Lexington, 

MA. The OIG followed-up missing records and issued subpoenas to compel the 

cooperation of four hospitals. 

The OIG contracted with the American Medical Record Association (AMR~ now 

named the American Health Information Management Association, or AHIMA) to 

1 
reabstract the charts. The AMRA selected ICD-9-CM codes supported by the record, 

determined the principal diagnosis, and grouped to select the correct DRG. To assure 

that the original ICD-9-CM codes and DRGs did not affect the reabstraction, the 

AMRA coders conducted their work without knowledge of the original ICD-9-CM 

codes and DRGs. The coders had instructions not to treat marginal problems or 

honest differences in judgment about appropriate coding as DRG errors. This 

standard should have produced a conservative estimate of the proportion of discharges 

having DRG errors. A series of reliability checks verified the reproducibility and 

accuracy of the AMRA coding. The AMRA also identified the reasons why a 

hospital’s bill differed from the correct codes. 

BOTEC Analysis Corporation of Cambridge, Massachusetts (BOTEC) edited the 

AMRA database, checked the sample’s representativeness, and conducted statistical 

analyses of the correlates and financial consequences of DRG 79 miscoding. It also 

reweighted the 1985 data to improve comparability with this inspection. Statistical 

tests determined whether numeric differences between 1985 results and 1988 results 

were real (statistically significant) or could be attributed to random error. 

Representativeness 

The sample generally resembled the underlying population of DRG 79 bills with 

respect to hospital and patient characteristics. The one exception to this was the 

distribution of the sample with respect to hospital size. [Appendix C]. 

2

Bed size 

sample Population 

Location 

Me@@ltan 

-w_ n 

sample Population 

Teachingstatus 

reteaching Nonteating 

Sample Population 

Control 

(’2” (a” 

Nonprofitu Nonprofitu 

sample Population 

Figure l: DRG79sample representativeness byhospital demography, 1988 

Age 

65-74 

65-74 

75-84 75-84 

+ 

Sample Population 

Sex 

Male 

Male 

Female Female 

Sample Population 

Race 

Q @;~’ 

Sample Population 

3 
FINDINGS 

Errors reduced 

Of the 123 sample discharges, 11 (8.9 

percent) were incorrectly assigned to 

DRG 79. This significantly improved 

upon the 18.4 percent error rate in 

1985.a Small hospitals billed more 

accurately than in 1985, and bills for 

patients less than 65 years old, and aged 

75-84, were more accurate than in 1985. 

[Appendix D]. 

The improvement in accuracy in DRG 

Peflferit 

20 

1 

15 

10 

5 

0[ 

DRG 79 

� 1988 

All DRGs 

79 differed significantly from the Figure 3: Proportion of DRG 79 and all 

improvement in all DRGs from 1985 to co’&ng errors; 1985 & 1988 

1988, from 20.8 percent in 1985 to 14.7 

percent in 1988. This inspection’s 8.9 percent DRG 79 error rate also differed 

significantly from the 14.7 percent of errors in all DRGs in 1988.3 

Most errors over-reimburse the hospitals 

Of the 11 billing errors, 90.9 percent 

over-reimbursed to the hospitals. This 

was not a significant improvement upon 

the 100.0 percent over-reimbursement 

reported in 1985. 

Hospitals still over-reimbursed 

The 123 sample discharges originally 

carried Relative Weights of 2.0777, 

Percent 

I I I Emr direction 

o 

-50 

100 

19ss 

Under-reimbursed 

Over-reimbursed 

equivalent to $6,478 in metropolitan Figure 4: Direction of DRG 79 errors, 1985 

hospitals and $5,479 in nonmetropolitan & 1988 

hospitals. The AMRA reabstraction, which resulted in 11 discharges reassigned to a 

DRG other than DRG 79, reduced the case-mix index (CMI) to 2.0057, a statistically 

a. Because of the smaller sample size that results from DRG-specific analysis, estimates 

of coding for specific DRGs are less precise than OIG’S national estimate. Statistical tests 

determined whether apparent differences were real (statistically significant) or could be 

attributed to random error. 

4 
significant decline of 0.0720. This 

reduction persisted across all hospital 

and demographic characteristics. The 

net CMI change in 1988 differed 

significantly from the net CMI change 

for DRG 79 bills in 1985. It also 

differed significantly from the net CMI 

change for all bills in 1988. [Appendix 

E]. 

Extrapolation of the 1988 CMI change 

to all 102,561 DRG 79 discharges 

projected that billing errors overreimbursed hospitals a statistically 

significant $22.7 million. This overreimbursement did not statistically differ 

$ gikm 

20-

lo0-

1985 1988 

Figure 5: DRG 79 over-reimbursement from 

miscoding, 1988 & 1985 

from the $28.4 million the OIG previously reported for 1985. The proportion of 

errors decreased over time, but the increase in DRG 79’s frequency completely offset 

the improvement in billing accuracy. 

Reasons for errors 

AMRA identified only two types of errors in the sample, misspecification and 

resequencing. No miscoding or other errors occurred. [Appendix F]. 

MissPecification	 The attending physician wrote down the wrong narrative diagnosis 

on the attestation. 

Resequencing	 The attending physician wrote the correct, narrative, principal 

diagnosis on the attestation, but the hospital substituted a 

secondary diagnosis for the principal diagnosis. 

Misspecification caused 81.8 percent of the 11 billing errors. This proportion 

significantly exceeded the 54.9 percent misspecificat~on errors in 1985.- It also 

significantly exceeded the 63.2 percent misspecifications for all DRGs in 1988. 

Resequencing caused 18.2 percent of the sample’s billing errors. This proportion did 

not significantly diffel from the 20.0 percent resequencing errors in 1985. 

5

ENDNOTES


1. Meyers M, Kleiman M, Stone D, Lee F, Schutte J, Hsia D, & Krushat M. DRG 79: 

respiratory infection. Washington, DC: HHS Office of Inspector General, 1989. Publication 

no. OAI-12-88-01190. 

2. Knight J W & Hsia D C, eds. National DRG Validation Study Update: Technical Report. 

Washington, DC: HHS Office of Inspector General, 1992. Publication no. OEI-12-90-00191. 

3. Knight J W & Hsia D C, eds. National DRG Validation Study Update: Summary Report. 

Washington, DC: HHS Office of Inspector General, 1992. Publication no. OEI-12-90-00190. 

6

. 

Health Care 

DEPARTMENTOF HEALTHa HUMAN SERVICES Financing Admmwtratlon 

Date 

From 

Subject 

To 

ax 519W Memorandum 

“%iiii29@ 9“ “ 

Acting Administrator 

Office of Inspector General (OIG) Draft Report: “DRG 79 Validation Study


Update: Respiratory Infections and Inflammations,” 0EI-12-89-O0193


Byan B. Mitchell


Principal Deputy Inspector General


We have reviewed the subject draft report which examined the coding accuracy 

of prospective payment discharges billed as diagnosis related group (DRG) 79. In a 

previous study, OIG sampled DRG 79 bills on a blinded basis and found upcoding 

that resulted in overpayment to hospitals of $28.4 million in 1985. 

In this repor~ OIG documented a significant improvement in coding accuracy 

for DRG 79, from over 81 percent in 1985 to over 91 percent in 1988. Despite this 

improvement the financial impact of DRG 79 billing errors was not reduced 

significantly because the errors continue to result in systematic overpayment to 

hospitals. In addition, hospitals billed a larger number of discharges to DRG 79 in 

1988. 

This report contained no recommendations for firther action, though OIG 

noted the findings of this report support the recommendation of an earlier and 

broader study: “National DRG Validation Study Update: Summary Report,” 

0EI-12-89-O0190. In this earlier repo~ OIG recommended that peer review 

organizations (PROS) continue their surveillance of hospital coding for DRG 

accuracy. 

We disagree with tie characteriution of certain billing mistakes as coding 

errors in situations where medical record coders are dependent on physician 

narratives. However, we agree with the broad recommendation about PROS 

surveillance of hospital bills for accuracy. 

Attached for your consideration are our detailed comments. Thank you for the 

opportunity to review and comment on this draft report. Please advise us whether 

you agree with our comments on the report at your earliest convenience. 

Attachment 

7 

s u.S. QOVSRNMENT PRINTING OFFICE: 1ss2 - 522-060/5182 
Comments of the Health Care Financing Administration (HCFA) 

on Office of the Ins~ector General (OIG) Draft Report: 

“DRG 79 Validation StudVU~date:Res~iratorv Infections and 

Inflammations.” OEI-12-89-00193 

General Comment 

The findings set forth in this report indicate that 81.8 percent (9 out of 11 cases) of 

DRG 79 billing errors uncovered by the audit were caused by the failure of the 

attending physician to indicate the principal diagnosis correctly in the narrative on the 

attestation. We would not characterize these as coding errors because medical record 

coders use a physician’s attested-to narrative when coding a Medicare discharge. Rather, 

this study points to problems with the physician narratives. 

Therefore, we agree with the broad recommendation that peer review organizations 

continue their sumeillance of hospital bills for accuracy including both physician 

descriptions of diagnoses and procedures, and the subsequent coding of narratives by 

medical record personnel. 

Technical Comments 

Page 1. ICD-9-CM should be written out as follows: International Classification of 

Diseases, Ninth Revision, Clinical Modification. 

Page 2. In October 1991, The American Medical Record Association (AMRA) formally 

changed its name to the American Health Information Management Association 

(AHIMA). Even though this audit was conducted under the auspices of AMRA, OIG 

may wish to make mention of this change in the introduction of this report. Suggested 

language is as follows: 

“OIG contracted with the American Medical Records Association (AMRA) to 

reabstract the charts. That association has since changed its name to the 

American Health Information Management Association (AHIMA), but will 

be referred to herein as AMRA.” 

. . 

8 
APPENDIX A 

Project participants 

OIG 

Cathaleen A. Ahern, B.A. 

Evan J. Buckingham, B.A. 

David C. Hsia, J.D., M.D., M.P.H. 

Thomas F. Komaniecki, M.P.A. 

W. Mark Krushat, M.P.H. 

Linda M. Moscoe, B.A. 

Brian P. Ritchie, B.A. 

Barry L. Steeleyb 

John M. Traczyk, B.A. 

HCFA 

Timothy F. Greene, M.A., M.B.A. 

Stephen F. Jencks, M.D. 

Michael R. McMullan, M.B.A. 

Harry L. Savitt, Ph.D. 

Jeanette M. Smith, M.D., M.P.H.c 

Malcolm A. Sneen, B.S. 

RAND Corporation 

Haya P. Rubin, M.D., Ph.Dd 

Baxter-Health Data Institutee 

Patricia J. Baxter, R.N. 

Patricia Cassidy-Tsnosas, R.N. 

Annette M. Delaney, R.N., M.A. 

Ellen B. Inghilleri, R.N. 

Janet Mathews, A.R.T. 

Laurie H. Moore, R.R.A. 

Claire Shannon, A.R.T. 

Michele A. Wiese, B.A. 

AMRA 

Margret K. Amatayakul, M.B.A., R.R.A. 

Mary Converse, R.R.A. 

b. Now at 

c. Now at 

d. Now at 

e. Ceased 

Health Audit Services, Ellicott City, MD. 

the Journal of the American Medical Association, Chicago, IL. 

Johns Hopkins Medical Institutions. 

operations February 16, 1990. 

A -1 
Nicholas J. Cotsonas, M.D.f


Linda Ertl, R.R.A.


Rita M. Finnegan, R.R.A.


Desla Mantilla, A.R.T.


Barbara Manny, R.R.A.


Sonia Martyniuk, R.R.A.


Toula Nicholas, A.R.T.


Charlotte Razor, R.R.A.


LouAnn Schraffenberger, R.R.A.


Lynn Smetko, R.R.A.


Dawn Smith, A.R.T.


Joan Zacharias, A.R.T.


BOTEC Analvsis Corporation


Geraldine M. Berenholz, R.R.A.


Andrew H. Chalsma, B.A.


David P. Cavanagh, M.A., Ph.D.


Janet W. Knight, R.N., Ph.D.


Amy L. Lockwood, B.A.


Contract information 

Contractor


BOTEC Analysis Corporation


1698 Massachusetts Avenue


Cambridge, MA 02138


Proiect Officer


David Hsia, J.D., M.D., M.P.H.


Office of Inspector General


330 Independence Avenue


Washington, D.C. 20201


Contract


HHS-1OO-9O-OO23


Firm-fixed price contract


$203,257


f. Outside contractor. 

A -2 
APPENDIX B 

ICD-9-CM codes in DRG 79 

003.22 

006.4 

010.0 

010.1 

010.8 

010.9 

011.0 

011.1 

011.2 

011.3 

011.4 

011.5 

011.6 

011.7 

011.8 

011.9 

012.0 

012.1 

012.2 

012.8 

020.3 

020.4 

020.5 

021.2 

022.1 

031.0 

039.1 

052.1 

055.1 

073.0 

095.1 

112.4 

114.0 

115.05 

115.15 

115.95 

121.2 

122.1 

130.4 

136.3 

482.0 

Salmonella pneumonia 

Amebic lung abscess 

Primary tuberculosis complex 

Primary tuberculosis pleurisy 

Primary progressive tuberculosis not elsewhere classifiable 

Prima~ tuberculosis not otherwise specified 

Tuberculosis 

Tuberculosis 

Tuberculosis 

Tuberculosis 

Tuberculosis 

Tuberculosis 

Tuberculosis 

Tuberculosis 

lung infiltrative 

lung nodular 

lung with cavity 

of bronchus 

lung fibrosis 

bronchiectasis 

pneumonia 

meumothorax 

Pulmonary tu~erculosis not elsewhere classifiable 

Pulmonary tuberculosis not otherwise specified 

Tuberculosis pleurisy 

Tuberculosis thoracic nodes 

Isolated tracheal tuberculosis 

Respiratory tuberculosis not elsewhere classifiable 

Primary pneumonic plague 

Secondary pneumonic plague 

Pneumonic plague not otherwise specified 

Pulmonary tularemia 

Pulmonary anthrax 

Pulmonary mycobacteria 

Pulmona~ actinomycosis 

Varicella pneumonitis 

Postmeasles pneumonia 

Ornithosis pneumonia 

Syphilis of lung 

Candidiasis of lung 

Primary coccidioidomycosis 

Histoplasma capsulatum pneumonia 

Histoplasma duboisii pneumonia 

Histoplasmosis pneumonia 

Paragonimiasis 

Echinococcus granulosus of the lung 

Toxoplasma pneumonitis 

Pneumocystosis 

K. Pneumonia pneumonia 

B-1 
482.1 Pseudomonas pneumonia 

482.4 Staphylococcus pneumonia 

484.1 Pneumonia with Cytomegalif 

484.3 Pneumonia in whoop cough 

484.5 Pneumonia in anthrax 

484.6 Pneumonia in aspergillosis 

inclusion disease 

484.7 

484.8 

507.0 

507.1 

507.8 

510.9 

511.1 

513.0 

513.1 

519.2 

510.0 

795.5 

v71.2 

Pneumonia in other systemic mycoses 

Pneumonia in infectious disease not elsewhere classifiable 

Food/vomit pneumonitis 

Oil/essence pneumonitis 

Solid/liquid pneumonitis not elsewhere classifiable 

Empyema without fistula 

Bacterial pleurisy with effusion not tuberculosis 

Abscess of lung 

Abscess of mediastinum 

Mediastinitis 

Empyema with fistula 

Tuberculin test reaction 

Observation for suspected tuberculosis 

B-2 
APPENDIX C


Sample representativeness 

Number [percent] Population 

Hospital demogra~hv 

1-99 beds 22,539 [22.0] 

100-299 beds 39,061 [38.1] 

300+ beds 40,918 [39.9] 

Metropolitan 72,185 [70.4] 

Nonmetropolitan 30,333 [29.6] 

Teaching 37,168 [36.3] 

Nonteaching 65,350 [63.7] 

Profit 13,910 [13.9] 

Nonprofit 86,303 [86.1] 

Patient demo~ra~hv 

<65 years 8,232 [8.0] 

65-74 years 25,384 [24.8] 

75-84 years 38,686 [37.7] 

85+ years 30,259 [29.5] 

Male 54,795 [53.4] 

Female 47,766 [46.6] 

White 89,424 [87.2] 

Black 8,579 [8.4] 

Other 1,808 [1.8] 

Unknown 2,750 [2.7] 

Sample 

37 [30.1] 

48 [39.0] 

38 [30.9] 

88 [71.5] 

35 [28.5] 

43 [35.0] 

80 [65.0] 

16 [13.0] 

107 [87.0] 

6 [4.9] 

29 [23.6] 

56 [45.5] 

32 [26.0] 

62 [50.4] 

61 [49.6] 

110 [89.4] 

10 [8.1] 

2 [1.6] 

1 [0.8] 

Chi-square 

5.04, 2 df, P= O.081 

0.06, 1 df, P= O.195 

0.07, 1 df, P= O.21O 

0.06, 1 df, P= O.199 

3.32, 3 df, P= O.652 

0.37, 1 df, P= O.451 

1.38, 3 df, P=0.289 

Total 102,561 [100.0] 123 [100.0] 

Note: Population frequencies may not sum to total because of missing cases. 

c-l

APPENDIX D 

DRG 79 billing erro~ 1985 and 1988 

Number [proportion 1988 

~ standard error] 

Hos~ital demo~ra~hy 

1-99 beds 1 [2.7 ~ 2.7] 

100-299 beds 6 [12.5 ~ 4.8] 

300+ beds 4 [10.5 t 5.0] 

Metropolitan 10 [11.4 t 3.4] 

Nonmetropolitan 1 [2.9 f 2.9] 

Teaching 5 [11.6 f 4.9] 

Nonteaching 6 [7.5 ~ 3.0] 

Profit 1 [6.3 ~ 6.3] 

Nonprofit 10 [9.3 t 2.8] 

Patient demo~ra~hv 

<65 years 2 [33.3 * 21.1] 

65-74 years 4 [13.8 A 6.5] 

75-84 years 3 [5.4 * 3.0] 

85+ years 2 [6.3 ~ 4.3] 

Male 2 [3.2 ~ 3.2] 

Female 9 [14.8 ? 4.6~ 

White 10 [9.1 t 2.8] 

Black o [0.0 t O.O] 

Other 1 [50.0 t 50.0] 

Unknown o [0.0 t 0.0] 

Total 11 [8.9 *2.6] 

1985 

24 [33.3 ~ 9.8] 

25 [20.0 ~ 8.2] 

25 [8.0 & 5.5] 

46 [28.5 f 6.9] 

28 [12.2 ~ 6.6] 

22 [9.3 * 4.7] 

52 [18.3 ~ 5.7] 

7 [13.8 t 8.0] 

67 [18.8 ~ 4.8] 

7 [0.0 t 0.0] 

19 [26.2 f 11.7] 

26 [50.8 ~ 15.6] 

22 [12.9 t 6.4] 

40 [13.3 * 4.1] 

34 [22.3 ~ 9.3] 

74 [18.4 ~ 4.4] 

t-test 

6.37 

1.41 

0.58 

3.09 

2.39 

0.53 

2.22 

2.14 

1.93 

6.51 

2.01 

6.39 

1.68 

3.23 

1.19 

L97 

D-1 
APPENDIX E


DRG 79 case-mix index change, 1985 and 1988 

Relative weight f 1988 

standard error 

Hos~ital demo~raphy 

1-99 beds -0.0213 ~ 0.0213 

100-299 beds -0.1149 t 0.0450 

300+ beds -0.0672 f 0.0456 

Metropolitan -0.0917 t 0.0314 

Nonmetropolitan -0.0226 f 0.0226 

Teaching -0.1075 ~ 0.0465 

Nonteaching -0.0529 ~ 0.0260 

Profit -0.0557 f 0.0557 

Nonprofit -0.0745 k 0.0257 

Patient demo~raphv 

<65 years -0.3657 & 0.2313 

65-74 years -0.1182 f 0.0564 

75-84 years -0.0230 ~ 0.0223 

85+ years -0.0608 * 0.0430 

Male -0.0271 ~ 0.0190 

Female -0.1177 t 0.0426 

Total -0.0720 f 0.0235 

1985 

-0.2960 f 0.0909 

-0.2086 ~ 0.0863 

-0.0861 t 0.0606 

-0.2623 t 0.0669 

-0.1278 f 0.0751 

-0.0865 t 0.0435 

-0.1916 f 0.0654 

-0.1401 ~ 0.0817 

-0.1834 ~ 0.0488 

0.0000 k 0.0000 

-0.2980 t 0.1379 

-0.4640 ~ 0.1486 

-0.1105 t 0.0568 

-0.1288 f 0.0407 

-0.2245 ~ 0.0988 

-0.1809 ~ 0.0457 

Difference t-test 

0.2747 6.31 

0.0937 1.79 

0.0189 0.44 

0.1706 3.25 

0.1052 2.53 

-0.0210 0.52 

0.1387 2.72 

0.0844 2.60 

0.1089 2.29 

-0.3657 6.51 

0.1798 2.75 

0.4410 6.73 

0.0497 1.34 

0.1017 3.48 

0.1068 1.67 

0.1089 2.34 

E-1

APPENDIX F 

Reasons for DRG 79 erro~ 1985 and 1988 

Number 

[percent] Total 1988 Total 1985 

Misspecification 9 [81.8] 6 [54.9] 

Miscoding o [0.0] 2 [13.3] 

Resequencing 2 [18.2] 3 [20.0] 

Other o [0.0] 4 [26.7] 

Total 11 [100.0] 15 [100.0] 

F -1