From Vital and Health Statistics of the National Center for Health Statistics Number 98 � July 20, 1984 

PFUIPERW OF m~ f 

PUBf.lCATl~NS 3RAI!JCH 

EDITORIALU3RARY 

Diagnosis-Related Groups Using Data From the


National Hospital Discharge Survey: United States, 1981


by Robert Pokras, Division of Health Care Statistics 

Introduction 

Thisreport presents selected estimates on diagnosis-related 

groups for 1981. These groups, developed at the Yale School 

of Organization and Management, are being used by the Health 

Care Financing Administration, some States, and some third 

party payers to reimburse hospitals for inpatient care.l This 

approach to health care reimbursement operates on the principle that patients with similar medical conditions should receive 

similar care and use approximately the same amount of resources; therefore, the hospital should be reimbursed the same 

amount. While there is variation in resource consumption 

among individuals within a diagnosis-related group, these are 

expected to balance across all patients. Diagnosis-related 

groups and prospective reimbursement are likely to play an 

increasingly important role in healh care financing in the future. 

�

The Health Care Financing Administration, which operates the Medicare program, is taking the next several years to 

make the transition to the use of diagnosis-related groups 

(DRGs) for hospital inpatient reimbursement. The phase-in 

period allows adjustments based on selected hospital characteristics and geographic locations so hospitals can adjust to this 

method of reimbursement. At the end of this time, care provided 

to an inpatient covered by Medicare in a specific DRG will 

translate into a preestablished amount of payment to the hospital regardless of its characteristics and location. 

DRG’s were developed under the guiding principle that 

“The primary objective in the construction of DRG’s was a 

definition of case type, each of which could be expected to 

receive similar outputs or services from a hospitaL”2 This was 

accomplished using clinical judgment and statistical procedures 

that classify patients by measuring resource utilization. The 

first step in this process was to cluster the universe of medical 

o	 diagnosis into broad, mutually exclusive categories. These 

groups were formed to be consistent in their anatomical or 

physiopathological classification, or in the manner in which 

‘they are clinically managed. Once these major diagnostic groups 

were formed, an interactive statistical program (AUTOGRP2) 

was used to further classify each major group into discrete 

DRG’s. This process incorporated patient information regarding dia~oses (primary and secondmy), procedures, sex, and 

age to explain maximally a patient’s resource use, which was 

approximated by a patient’s length of stay. In all, there are 

currently 470 DRGs. 

There are many important issues to be studied concerning 

a change in reimbursement procedures, most of which are 

beyond the scope of this paper. One issue relevant to the National Hospital Discharge Survey (NHDS) is how this sytem 

may affect the selection of a patient’s principal diagnosis. For 

example, two patients admitted to the hospital for treatment of 

chest pain-one diagnosed as having chest pain and the other 

diagnosed as having angina-will have different reimbursement 

rates. 1There is speculation that DRG reimbursement may influence the selection of a diagnosis in cases such as this. If so, 

changes may show up in fhture DRG estimates produced from 

NHDS data. The estimates in this report can be viewed as a 

baseline tQ compare fhture estimates of DRG’s. 

The statistics in this report are based on data collected by 

means of the NHDS, a continuous survey conducted by the 

National Center for Health Statistics since 1965. Data for this 

survey are sampled from short-stay non-Federal general and 

specialw hospitals in the 50 States and the District of Columbia. 

The sample for 1981 contained approximately 227,000 medical 

records from 428 hospitals. The relevant variables required to 

produce DRG’s (diagnoses, procedures, sex, age, and other 

variables) were abstracted from the face sheet of each sampled 

medical record, and the NHDS could thereby produce national 

estimates of DRG’s. These estimates may be of value for hospitals to compare their experience with that of other hospitals. 

For this reason, statistics in this report are frequency estimates 

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service 
--

2 achancedata 

and associated average length of stay for DRG’s by hospital 

bed size and region of the country. 

Highlights 

The frequency and average length of stay for the most 

common DRG’s are presented by age, region of the country, 

and hospital bed size (tables 1-4). Age is dichotomized as 

under 65 years of age and 65 yeak of age and older. This 

allows a comparison with the Medicare population because 

Medicare covers most hospital costs for approximately 94 percent of discharges 65 years of age and over. Tables 1 and 2 

provide regional data, while tables 3 and 4 provide bed-size 

data for these DRG’s. Within each of these sets of tables, the 

first (tables 1 and 3) are for patients under 65 years of age, and 

the second (tables 2 and 4) are for patients 65 years of age 

and over, 

By deftition, some DRGs are only for patients in a specitic 

age range. In such a case the DRG title and the table “ 

(tables 1-4) together define the age group of the estimate. T 

is, the most restrictive case of either the table or DRG * tit 

determines the age group of the estimate. For example, 

“Diabetes, age greater than 35 years” in table 2 only refers to 

patients 65 years of age and over because of the table title; 

whereas, “Simple pneumonia and pleurisy, age greater than 

69 years and/or substantial comorbidity and complication” in 

table 2 would not include a patient under 70 years of age because of the restriction in the DRG title. 

The most common DRG for patients under 65 years 

of age is vaginal delivery without complicating diagnoses 

(table 1), with an estimated 2.8 million discharges in 1981. 

Cesarean section, with 631,000 discharges, was also among 

the most frequent DRG’s in this age group. For patients 65 

years of age and older (table 2), atherosclerosis is the most 

Table 1. Number of discharges and average length of stay of patients under 66 years of age discharged from short-stay hospitals, by 

selected diagnosis-related groups and geographic region: United States, 1981 

[Discharges from non-Federal short-stay hospitsls. Excludes newborn infants] 

All North All North 

Diagnosis-related group regions Northeast Central South West regions Northest Central South West 

Number in thousands Averaae Ienath of stav., in davs 

All discharges . . . . . . . . . . . . . . . . . . . . . 28,136 5,621 8,177 9,715 4,624 5.9 6.6 6.2 5.7 5.1 

Vaginal delivery without complicating 

diagnoses . . . . . . . . . . . . . . . . . . . . . . . . . 2,790 517 796 922 555 3.0 3.5 3.5 2.8 

Medical back problems . . . . . . . . . . . . . . 800 126 267 280 127 7.2 8.9 7.4 6.9 5. e 

Esophagitis, gastroenteritis, and miscellaneous digestive disorders, ages 18-69 

years without substantial comorbidity 

and/or complication . . . . . . . . . . . . . . . 688 83 188 340 76 4.3 5.0 4.3 4.3 3.3 

Cesarean section without substantial 

comorbidity and/or complication. . . . . . . 631 133 154 228 115 6.1 7.3 6.3 5.7 5.0 

Nonradical hysterectomy, age less than 

70 years without substantial comorbidity 

snd/or complication . . . . . . . . . . . . . . . 527 71 130 218 109 7.3 8.2 8.0 7.1 6.1 

Unrelated operating room procedures. . . . 406 71 117 148 70 10,7 14.3 10.4 10.1 8.8 

Alcohol- and substance-induced organic 

mental syndrome . . . . . . . . . . . . . . . . . 403 182 112 66 44 10<0 B.7 12.8 9.9 8.6 

Dilation and curettage of uterus, ionization except for malignancy. . . . . . . . . . . . 392 114 101 135 42 1.9 1.7 2.0 2.2 1.2 

Psychoses . . . . . . . . . . . . . . . . . . . . . . . . . . 383 99 129 86 69 16.9 20.1 17.0 13.3 16.4 

Esophagitis, gastroenteritis, and miscellaneous digestive disorders, ages 

O-17 years . . . . . . . . . . . . . . . . . . . . . . . 379 68 110 168 32 3.7 3.9 3.4 3.7 4.0 

Abortion with dilation and curettage of 

uterus . . . . . . . . . . . . . . . . . . . . . . . . . . . 355 140 71 101 44 1.4 1.1 1.8 1.6 1.1 

Bronchitis and asthma, ages O–1 7 

years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 62 95 108 33 4,1 4.3 4.2 4.3 2.9 

Tonsillectomy and/or adenoidectomy, 

ages O-17 years . . . . . . . . . . . . . . . . . 295 49 109 90 48 1.7 1.6 1.8 2.0 1.3 

Inguinal and femoral hernia procedures, 

ages 18-69 years without substantial 

comorbidity and/or complication, . . . . . . 253 68 71 67 47 4.4 4.4 %7 4.9 3.2 

Diabetes, age more than 35 years. . . . . . . 249 52 66 103 27 8.1 10.8 7.7 7.4 6.9 

Vaginal de!ivery with sterilization and/or 

dilation and curettage of uterus. , . . . . . . 246 39 51 119 37 3.6 4.5 3.9 3.4 3.1 

Simple pneumonis and pleurisy, ages 

O-17 years . . . . . . . . . . . . . . . . . . . . . . . . 243 29 70 120 25 5.1 5.6 5.1 5.2 3. 

Knee procedures, age less than 70 years 

without substantial comorbidity and/or a 

complication . . . . . . . . . . . . . . . . . . . . . . . 232 39 85 59 48 4.6 5.3 4.2 5,3 3.7 

Hypertension . . . . . . . . . . . . . . . . . . . . . . . . 229 38 60 102 29 5.9 6.3 6.5 5.6 5.3 

Otitis media and upper respirator 

infection, ages 0-17 years. , . . . . . . . . . . 227 37 71 99 20 3.3 3.5 3.1 3.5 2,8 
dmcedaa3 

Table 2. Number of discharges and average length of stay of patienta 65 years of age and over from short-stay hospitals, by selected diagnosisrelated groups and geographic region: United States, 1961 

ischarges from non-Federal short-stay hospitals. Excludes newborn infants] 

All North All North 

Diagnosis-related group regions Northeast Central South West regions Northeast Central South West 

Number in thousands Average length of stay in days 

All discharges . . . . . . . . . . . . . . . . . . . . . . . 10,408 2,201 2,955 3,4B8 1,764 10.5 13.1 10.6 9.9 8.3 

Atherosclerosis, age greater than 69 yeara 

and/or substantial comorbidity and complacation . . . . . . . . . . . . . . . . . . . . . . . . . . . 422 93 107 161 60 9.4 11.7 9.5 B.9 6.8 

Lens procedures . . . . . . . . . . . . . . . . . . . . . 387 75 114 100 97 3.2 3.4 3.4 3.1 2.9 

Esophagitis, gastroenteritis, and miscellaneous digestive disorders, age greater 

than 69 years and/or substantial comorbidity and complication . . . . . . . . . . . . . . 372 58 111 154 49 7.0 8.9 7.0 6.9 5.4 

Heart failure and shock . . . . . . . . . . . . . . . . 363 83 100 122 59 9.9 12.6 9.9 9.1 7.5 

Chronic obstructive pulmonary disease. . . 304 59 79 116 50 9.9 11.7 10.0 9.3 9.0 

Specific cerebrovascular disorders except 

transient ischemic attack. . . . . . . . . . . . . 294 67 83 95 48 15.8 20.4 14.7 15.2 12.2 

Simple pneumonia and pleurisy, age 

greater than 69 years and/or substantial 

comorbidity and complication . . . . . . . . . 281 50 75 114 41 11.2 13.9 11.4 10.5 9.7 

Diabetes, age greater than 35 years . . . . . 218 44 61 90 23 9.9 14.1 9.4 8.9 7.4 

Unrelated operating room procedures. . . . 211 55 66 62 28 18.5 24.8 16.1 17.2 14.3 

Circulatory disorders with acute myocardial infarction without cardiovascular 

complications, discharged alive. . . . . . . . 179 42 44 56 37 12.6 14.1 13.7 12.5 9.6 

Medical back problems . . . . . . . . . . . . . . . 173 31 49 64 28 8.8 10.1 8.6 8.4 8.4 

Cardiac arrhythmia and conduction disorders, age greater than 69 years and/ 

or substantial comorbidity and complication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16B 36 49 51 32 7.3 9.0 8.2 6.9 5.1 

Hypertension . . . . . . . . . . . . . . . . . . . . . . . . 162 26 47 68 22 7.7 9.5 7.6 7.7 5.7 

nginapectoris . . . . . . . . . . . . . . . . . . . . . . 161 35 47 58 21 7.0 8.4 8.0 6.1 5.1 

ansient ischemic attacks. . . . . . . . . . . . . 150 35 39 53 24 7.6 10.3 8.1 6.7 4.9 

@ ransurethral prostatectomy, age greater 

than 69 years and/or substantial comorbidity and complication . . . . .’ . . . . . . . . . 140 32 39 44 24 10.5 13.4 10.7 9.9 7.3 

Bronchitis and asthma, age greater than 

69 years and/or substantial comorbidity 

and complication . . . . . . . . . . . . . . . . . . . 126 25 34 46 21 8.7 12.0 8.4 8.2 8.6 

Gastrointestinal hemorrhage, age graater 

than 69 years and/or substantial comorbidity and complication . . . . . . . . . . . . . . 126 29 34 39 24 9.2 11.2 9.5 9.4 6.3 

Respiratory neoplasms. . . . . . . . . . . . . . . . 126 33 29 40 23 11.3 13.4 11.1 11.4 8.3 

Kidney and urinary tract infections, age 

greater than 69 years and/or substantial comorbiditysnd complications . . . . . 124 19 30 59 16 9.3 11.0 9.8 9.2 6.4 

.-. 

common DRG, 422,000, and lens procedures, 387,000, is the 

second most common DRG for the elderly. 

The average length of stay for specific DRG’s in the four 

regions of the country generally reflects the pattern found for 

all patients: the northeast has the longest average length of stay 

and the west has the shortest. Regional length-of-stay differences are greater for patients 65 years of age or more than for 

younger patients. The west has an average length of stay of 5.1 

days for patients under 65 years of age and the northeast has 

an average length of stay of 6.6 days; a dtierence of 1.5 days, 

or 29.4 percent greater. For older patients, however, the northst has an average length of stay 4.8 days greater than the 

derly patients in the west ( 13.1 versus 8.3 days), a difference 

@ of 57.8 percent. 

Overall there is a tendency for length of stay to increase 

with hospital bed size (table 3 and 4) for patients under 65 

years of age as well as for older patients, but t.hk pattern is not 

consistent for some of the individual DRG’s. For example, 

patients with psychoses under 65 years (table 3) had a longer 

length of stay in the smallest hospitals, and for some DRG’s 

the average length of stay in medium-size hospitals is equal to 

or greater than the average length of stay in large hospitals 

(500 or more beds). 

The average length of stay associated with a DRG (tables 

1–4) allows hospitals to compare their experience with that of 

other hospitals. While comparison is tenuous on a case-bycase basis, a hospital with an average length of stay 2, 3, or 

more days longer than the national average for a specific DRG 

may need to examine why it is so far fkom the norm. This kind 

of comparison may be worthwhile as a starting point, but even 

within a DRG, average length of stay is not an exact measure 

of resource consumption. 
Table 3. Number of discharges and average length of stay of patients under 66 years of age discharged from short-stay hospitals, by selected diagnosis-related groups and hospital bed size: 

United States, 1981 

[Discharges from non-Federal short-stay hospitals, Excludes newborn infants] 

All 6–99 100-199 200-299 300-499 500 or All 6-99 700-199 200–299 300-499 500 or 

Diagnosis-related group hospitals beds beds beds beds more beds hospitals beds beds beds beds more beds 

Number in thousands Average Iangth of stay in days 

Alldischargas . . . . . . . . . . . . . . . . . . . . . . . . . . . 28,136 4,783 5,149 4,351 6,874 6,979 5.9 4.7 5.4 5,7 6.3 7.0 

Vaginal delivery without complicating diagnoses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,790 422 488 454 672 755 3.0 2.5 2.9 2.8 3.3 3.3 

Medical back problems . . . . . . . . . . . . . . . . . . . 800 159 155 133 193 159 7.2 6.6 7.0 6.8 7.6 7.8 

Esophagitis, gastroenteritis, and miscellaneous digestive disordars, ages 18-69 years 

without substantial comorbidity and/or complacation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 688 204 132 106 134 112 4.3 3.7 4.2 4.6 4.5 4.9 

Cesarean section without substantial comorbidity and/or complication. . . . . . . . . . . . . . . . 631 76 122 91 159 182 6.1 5.7 5.5 6.0 6.2 6.4 

Nonradical hysterectomy, age less than 70 

years without substantial comorbidity and/ 

or complication . . . . . . . . . . . . . . . . . . . . . . . . . 527 70 127 87 110 133 7.3 7.1 6.6 7.2 7.5 7.8 

Unrelated operating room procedures . . . . . . . 406 49 72 67 99 118 10.7 7.2 8.2 11.0 11.0 13.2 

Alcohol- and substance-induced organic 

manta l syndrome . . . . . . . . . . . . . . . . . . . . . . 403 133 61 48 96 65 10.0 8.3 11.0 13.9 9.4 10.9 

Dilation and curettage of uterus, ionization 

except for malign ancy . . . . . . . . . . . . . . . . . 392 66 82 50 99 95 1.9 2.0 1.7 2.0 1.9 2.0 

Psychoses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 44 54 46 122 117 16.9 22.0 5.4 12.2 17.5 16.8 

Esophagitis, gastroenteritis, and miscellaneous digestive disorders, ages O–1 7


years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 74 87 59 91 67 3.7 3.0 3.6 4.1 3.6 4.1


Abortion with dilation and curettage of


uterus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355 40 65 46 83 122 1.4 1.8 1.3 1.5 1.6 1.1 

Bronchitis and asthma, agas O–1 7 yeara . . . . . 299 55 75 43 70 56 4.1 3.3 4.3 4.6 4.3 3.9 

Tonsillectomy and/or adenoidectomy, ages 

0–17 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295 52 61 62 67 53 1.7 1.8 1.9 1.6 1.6 1.8 

Inguinal and femoral hernia procedures, agas 

18–69 years without substantial comorbidity 

and/or complication . . . . . . . . . . . . . . . . . . . . . 253 41 44 43 73 53 4.4 4.6 4.3 4.5 4.3 4.4 

Diabetes, age more than 35 years. . . . . . . . . . . 249 57 42 41 57 51 8.1 6.8 7.8 8.0 9.3 8.5 

Vaginal delivery with sterilization and/or dilation and curettage of uterus. . . . . . . . . . . . . . . 248 47 53 31 48 67 3.6 3.3 3.4 3.5 3.8 4.0 

Simple pneumonia and pleurisy, ages O–1 7 

years . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . 243 75 57 39 38 34 5.1 4.2 5.3 6.0 5.3 5.1 

Knee procedures, age less than 70 years 

without substantial comorbidity and/or complacation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 22 33 53 66 59 4.6 4.2 4.2 4.6 4.9 4.6 

Hypertension . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 56 45 33 52 43 5.9 5.0 5.8 6.2 6.1 7.0 

Otitis media and upper respirato~ infection, 

ageao—17 y ears.. . . . ... . . . . . . . . . . . . . . . . 227 58 59 34 43 33 3.3 2.9 3.3 3.6 3.2 3.8 
Table 4. Number of discharges and average length of stay of patients 65 years of age and over discharged from short-stay hospitals, by selected diagnosis-related groups and 

hospital bad size: United Statas, 1981 

[Discharges from non-f+ deral short-stay hospitals. Excludes newbOrn infants] 

All 6-99 100-199 200-299 300-499 500 or All 6-99 100– 199 200-299 300-499 500 or 

Diagnosis-related group hospitals beds beds beds beds more beds hospitals beds beds beds beds more beds 

Number in thousands Average length of stay-in days 

All discharges . . . . . . . . . . . . . . . . . . . . . . . . . . . 10,406 2,160 1,667 1,741” 2,543 2,097 10,5 8.3 9.6 10.9 11.3 11,9 

Atherosclerosis, age greater than 69 years 

snd/or substantial comorbidity and complication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422 93 65 79 98 9.4 7.3 9.1 9.6 10.5 10.5 

Lens procedures . . . . . . . . . . . . . . . . . . . . . . . . . 387 32 79 77 115 82 3,2 3.2 3.2 3.1 3.1 3.3 

Esophagitis, gastroenteritis, and miscellaneous digestiva disorders, age graater than 

69 years and/or substantial comorbidity and 

complication . . . . . . . . . . . . . . . . . . . . . . . . . . . 372 127 69 58 73 46 7.0 6.3 7.0 7.2 7.8 7.4 

Heart failure andshodk . . . . . . . . . . . . . . . . . . . 363 105 67 61 74 56 9.9 8.6 9.8 9.3 11.2 1.1 

Chronic obstructive pulmona~ disease . . . . . . 304 89 62 46 64 42 9.9 8.4 10.2 10.2 10.8 0.9 

Specific cerebrovascular disorders except transientischemic attack...,,, . . . . . . . . . . . . . . 294 66 56 47 70 54 15.8 12.2 14.9 18.2 16.6 7.4 

Simple pneumonia and plaurisy, age greater 

than 69 years and/or substantial comorbidity 

and complication, . . . . . . . . . . . . . . . . . . . . . . 261 101 47 38 57 37 11.2 10.1 10.7 13.1 12.5 1.2 

Diabetes, age greater than 35 years . . . . . . . . . 218 56 44 36 50 32 9.9 8,1 10.7 10.0 10.6 10,7 

Unrelated operating room procedures , . . . . . . 211 22 42 39 57 51 18.5 13.1 15,3 20.3 18.5 21,9 

Circulato~ disorders with acuta myocardial 

infarction without cardiovascular complications, discharged a live, . . . . . . . . . . . . . . . . . . 179 38 28 36 44 31 12.6 10.4 13.2 12.3 14.0 13.1 

Medicai back problems ...,,.,, . . . . . . . . . . . 173 47 32 26 39 29 8.8 8.1 7.9 8.5 9.6 10.1 

Cardiac arrhythmia and conduction disorders, 

age greater than 69 years and/or substantial 

comorbidity and complication . , . , . , . . . , . , , 168 45 29 26 33 33 7.3 5.8 6.2 7.7 7,8 9.6 

Hypertension . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 50 35 24 27 26 7.7 6,9 7,7 7,8 7.9 8.9 

Angina pectoris. ,,, . . . . . . . . . . . . . ... ,,, ,., 161 46 31 23 39 22 7.0 5,6 6.7 8.3 7.7 7.8 

Transient ischemic attacks . . . . . . . . . . . . . . . . 150 37 30 30 34 19 7.6 5.6 6,3 7.6 10.0 9,2 

Transurethral prostatectomy, age greater than 

69 yaars and/or substantial comorbidity and 

complication . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 18 33 22 34 33 10,5 9.7 10.2 9.6 10.6 11.7 

Bronchitis and asthma, age greater than 60 

yaars and/or substantial comorbidity and 

complication . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 38 26 17 26 17 8.7 6.8 8.9 9.1 10.6 9.3 

Gastrointestinal hemorrhage, age greater than 

69 yaars and/or substantial comorbidity and 

complication . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 26 21 19 34 24 9.2 7.2 9.4 9.5 10.1 9.6 

Respiratory neoplasms. . .,,,,.... . . . . . . . . . 126 15 18 21 35 36 11.3 11.4 9,9 12.3 11.7 10.9 

Kidney and urinary tract infections, age greater 

than 69 years and/or substantial comorbidity 

and complication .,,..... . . . . . . . . . . . . . . . 124 43 24 14 25 18 9.3 8.4 8.8 9.6 10.0 10.5 
6 advamedata 

References 

lJ. Alsofrom: Playing the numbers. Medical World News, Oct. 24, 

1983, pp. 38-55. 

2R. B. Fetter, S. Youngsoo, J. L. Freeman, and others: Case mix 

definition by diagnostic related groups. Medical Care 18(2), Supplement. (Copyright 1980 Used with the permissionof Medical Care. ) 

3National Center for Health Statistics, M. G. Sirken: Utilization of 

short-stay hospitals, Summary of nonmedical statistics, United States, 

1965. Vital and Health Statistics. Series 13, No. 2. PHS Pub. No. 

1000. Public Health Service. Washington. U.S. Government Printing 

OtlIce, Aug. 1967. 

4National Center for Health Statistics, M. J. Witkin: Utilization of 

short-stay hospitals by characteristics of discharged patients, United 

States, 1965. Vital and HeaWz Statistics. Series 13, No. 3. PHS Pub. 

Technical notes 

Survey methodology 

Source of data 

The National Hospital Discharge Survey (NHDS) encompasses patients discharged from short-stay hospitals, exclusive 

~f military and Veterans Administration hospitals, located in 

&e 50 States and the District of Columbia. Only hospitals with 

six or more beds and an average length of stay of less than 30 

days for all patients are included in the survey. Discharges of 

newborn infants are excluded from this report. 

The universe of the survey consisted of 6,965 short-stay 

hospitals contained in the 1963 Master Facility Inventory of 

Hospitals and Institutions. New hospitals were sampled for 

inclusion in the survey in 1972, 1975, 1977, and 1981. The 

,sample for 1981 consisted of 550 hospitals. Of these, 71 re­

,fused to participate, and 51 were out of scope either because 

the hospital had gone out of business or because it failed to 

meet the definition of a short-stay hospital. Thus 428 hospitals 

participated in the survey during 1981 and provided approximately 227,000 abstracts of medical records. 

Sample design 

All hospitals with 1,000 or more beds in the universe of 

short-stay hospitals were selected with certainty in the sample. 

All hospitals with fewer than 1,000 beds were stratified, the 

primary strata being 24 size-by-region classes. Within each of 

these 24 primary strata, the allocation of the hospitals was 

made through a controlled selection technique so that hospitals 

in the sample would be properly distributed with regard to type 

of ownership and geographic division. Sample hospitals were 

drawn with probabilities ranging from certainty for the largest 

hospitals to 1 in 40 for the smallest hospitals. 

Sample discharges were selected within the hospitals using 

No. 1000. Public Health Service. Washington. U.S. Government 

Printing Office, Dec. 1967. 

5National Center for Health Statistics, R. Pokras: Surgical and non-@ 

surgical procedures in short-stay hospitals, United States, 1979. Vital 

and Health Statistics. Series 13, No. 70. DHHS Pub. No. (PHS) 

83-1731. Public Health Service. Washington. U.S. Government 

Printing OffIce, Feb. 1983. 

6U.S. Public Health Service and Health Care Financing Administration: International Classl~cation of Diseases, 9th Revision, Clinical 

Modification. DHHS Pub. No. (PHS) 80-1260. Public Health Service. Washington. U.S. Government Printing OffIce, Sept. 1980. 

TFederaz Register. Vol. 48, No. 171, Part II, Rules and Regulations, 

Sept. 1, 1983. 

the daily listing sheet of discharges as the sampling frame. 

These discharges were selected by a random technique, usually 

on the basis of the terminal digit or digits of the patient’s medical 

record number, a number assigned when the patient was admitted to the hospital. The within-hospital sampling ratio fo 

selecting sample discharges varied inversely with the probabilityQ 

of selection of the hospital. 

Data collection and estimation 

The sample selection and the transcription of information 

from the hospital records for abstract forms were performed by 

the hospital staff or by representatives of the National Center 

for Health Statistics or by both. The data were abstracted from 

the face sheets of the medical records. All discharge diagnoses 

were listed on the abstract in the order of the principal one, or 

the first-listed one if the principal one was not identified, followed by the order in which all other diagnoses were entered 

on the face sheet of the medical record. 

Statistics produced by NHDS are derived by a complex 

estimating procedure. The basic unit of estimation is the sample 

inpatient dkcharge abstract. The estimating procedure used to 

produce essentially unbiased national estimates in NHDS has 

three principal components: inflation by reciprocals of the 

probabilities of sample selection, adjustment for nonresponse, 

and ratio adjustment to fixed totals. These components of estimation are described in appendix I of two earlier publications. 374 

Diagnosis-related groups 

The diagnosis-related groups (DRG’s) used in this report 

were produced using the most current DRG program availabl 

at the time (summer of 1983). This is a computer program th 

a groups patients into DRG’s based on diagnostic, surgical, and 

NOTE: A list of referencesfollowsthe text. 
dmncewa7 

* 

patient information. The program is maintained and is comercially available at Health Systems International (DRG 

upport Group, 100 Broadway, New Haven, Corm. 06511). 

However, the actual program used to produce estimates in this 

report was obtained from the Health Care Financing Administration. 

To help interpret the data in this report, two points are 

worth mentioning. First, the entire NHDS file was used to 

produce estimates, including outliers. None of the data was 

excluded, or trimmed, because of an abnormally long length of 

stay. Second, the NHDS only codes three ICD–9–CM Class 4 

procedures:5’s circumcision, code 64.0; episiotomy, code 73.6; 

and removal of intrauterine contraceptive device, code 97.71. 

In certain instances Class 4 procedures can alter the DRG 

designation for a patient. The effect of not coding these procedures in the NHDS on determining DRG’s is unknown, but 

probably quite small. In all other respects, the DRG’s presented 

in this report are consistent with those in the Federal Register 

of Thursday, September 1, 1983.7 

In publications from the National Center for Health Statistics using NHDS data, several schemes have been used to 

group patients into categories based on either their diagnoses 

or the procedures performed. These groups were developed to 

report general purpose statistics to the many users of NHDS 

data, and any similarity between the titles of those categories 

and DRG titles is coincidental. 

e ampiing errors and rounding of numbers 

The standard error is a measure of the sampling vanabili~ 

@ 

that occurs by chance because only a sample, rather than & 

entire universe, is surveyed. The relative standard error of the 

estimate is obtained by dividing the standard error by the estimate itself and is expressed as a percent of the estimate. Table I 

shows relative standard errors for discharges and fwst-listed 

diagnoses for 1981. The standard errors for average lengths of 

stay are shown in table II. Estimates have been rounded to the 

nearest thousand. For this reason detailed figures within tables 

do not always add to the totals. 

Tests of significance 

In this report, the determination of statistical inference is 

based on the two-tailed Bonfemoni test for multiple comparisons. 

Terms relating to differences, such as “higher” and “less:’ 

NOTE: A list of references follows the text. 

Tabla 1. Approximate relative standard errors of estimated number 

of discharges and first-listed diagnoaes: United States, 1981 

Relative 

standard 

Size of estimate error 

0,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.3 

,000........................................ 10.2


00,000....................................... 8.5


300,000....................................... 6.6


500,000....................................... 5.9


1,000,000
..................................... 5.7


4,000,000..................................... 4.0


Table 11. Approximate standard errors of average lengths of stey 

by number of discharges: United States, 1981 

Average length of stay 

in days 

Number of discharges 2 6 10 20 

Standard error in days 

10,000 . . . . . . . . . . . . . . . . . . . 0.7 1.2 1.7 2.2 

50,000................... 0.3 0.7 1.0 1.4 

100,000.................. 0.3 0.6 0.9 1.2 

500,000.................. 0.2 0.5 0.8 0.9 

1,000,000................ 0.2 0.5 0.8 0.7’ 

5,000,000................ 0.2 0.5 0.8 ... 

indicate that the differences are statistically significant. Terms 

such as “similar” or “no difference” mean that no statistically 

signii5cant difference exists between the estimates being compared. A lack of comment on the difference between any two 

estimates does not mean that the difference was tested and 

found to be not significant. 

Definition of terms 

Patient—A person who is formally admitted to the inpatient 

service of a short-stay hospital for observation, care, diagnosis, 

or treatment. In this report the number of patients refers to the 

number of discharges during the year, including any multiple 

discharges of the same individual from one or more shoti-stay 

hospitals. 

Average length of stay—The total number of patient days 

accumulated at time of discharge by patients discharged during 

the year divided by the number of patients discharged. 

Age—Patient’s age refers to age at birthday prior to a& 

mission to the hospital inpatient service. 

Discharge—Discharge is the formal release of a patient by 

a hospital; that is, the termination of a period of hospitalization 

by death or by disposition to place of residence, nursing home, 

or another hospital. The terms “discharges” and “patients discharged” are used synonymously. 

Geographic region—Hospitals are classified by location 

in one of the four geographic regions of the United States that 

correspond to those used by the U.S. Bureau of the Census: 

Region States included 

Northeast. . . . . . Maine, New Hampshire, Vermont, Massachusetts, Rhode laland, Connecticut, New 

York, New Jersey, and Pennsylvania 

North Central. . . Michigan, Ohio, Illinois, Indiana, Wisconsin, Minnesota, lowa, Missouri, North 

Dakota, South Dakota, Nebraska, and 

Kansas 

South . . . . . . . . . Delaware, Maryland, District of Columbia, 

Virginia, West Vkginia, North Carolina, 

South Carolina, Georgia, Florida, Kentucky, Tennessee, Alabama, Mississippi, 

Arkansas, Louisiana, Oklahoma, and 

Texas 

West . . . . . . . . . Montana, Idaho, Wyoming, Colorado, New 

Mexico, Arizona, Utah, Nevada, Washington, Oregon, California, Hawaii, and 

Alaska 
8 aduancedata 

Hospitals—Short-stay special and general hospitals have beds, cribs, and pediatric bassinets regularly maintained (set 

six or more beds for inpatient use and an average length of stay up and staffed for use) for patients; bassinets for newborn inof less than 30 days. Federal hospitals and hospital units of fants are not included. In this report the classification of h 

institutions ar6 not included. pitals by bed size is based on the number of beds at or ne* 

Bed size of hospital—Size is measured by the number of midyear reported by the hospitals. 

Recent Issues of Advance Data From Vital and Health Statistics 

No. 97. The Management of New Pain in Office-Based Ambulatory 

Care: National Ambulatory Medical Care Survey, 1980 and 1981 

(Issued June 13, 1984) 

No. 96. Utilization of Analgesic Drugs in Ollice-Based Ambulatory 

Care: National Ambulatory Medical Care Survey, 1980–81 (Issued 

March 14, 1984) 

No. 95. 1982 Summary: National Hospital Discharge Survey (Issued 

December 27, 1983) 

Suggested Citation


National Center for Health Statistic, R. Pokras:


Diagnoaia-related groups using data from the


National Hospital Discharge Survey: United Statea,


1981. Advance Data From Vital and Health


Statistics, No. 98. DH HS Pub. No. (PHS) 84-1250.


Public Health Service. Hyattaville, Md., July 20, 1984


U.S. DEPARTMENT OF HEALTH AND 

HUMAN SERVICES 

Public Health Service 

National Center for Health Statistics


3700 East-West Highway


Hyattsville, Maryland 20782


OFFICIAL 8USINESS


PENALTY FOR PRIVATE USE, $300


To receive this publication regularly, contact


the National Center for Health Statistics by


calling 301 436-NCHS.


DHHS Publication No. (PHS) 84-1250


No. 94. Discharge Status of Inpatients Discharged From Short-Stay 

Hospitals: United States, 1965-81 (Issued November 22, 1983) 

No. 93. Utilization of Short-Stay Hospitals by Adolescents: United 

States, 1980 (Issued September 14, 1983) 

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