From Vital and Health Statlstlcs of the National Center for Health Statlstlcs January 18, 1985 � Number 105 

9 

PI?OPER’WOFWt 

PUBLICATKINSBRANCH 

EDITORIALIJ5RARY 

Diagnosis-Related Groups Using Data From the 

National Hospital Discharge Survey: United States, 1982 

by Robert Pokras and Kurt K. Kubishke, Division of Health Care Statistics 

* 

m 

Introduction 

This report presents selected estimates for 1982 of 

diagnosis-related groups (DRG) based on data from the National Hospital Discharge Survey (NHDS). A similar report 

as been published for 1981.1 The current plan is to publish 

orts on DRGs regularly because they determine the reimrsement rates of Medicare inpatients, about 30 percent of all 

discharges from shofi-stay non-Federal hospitals.z 

Developed at the Yale School of Organization and Management, DRG’s are being used by the Health Care Financing 

Administration, some States, and some third party payers to 

reimburse hospitals for inpatient care on a prospective basis.3 

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, in general a hospital should be reimbursed 

the same amount for each patient in a DRG. While there is 

variation h resource consumption among individuals within a 

DRG, these are expected to balance across all patients. 

DRG’s were developed under the guiding principle that 

“The primary objective in the construction of DRGs was a 

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

receive similar outputs or services from a hospital.”4 Their 

formulation was accomplished using clinical judgment and 

statistical procedures that classifi patients by measuring resource utilization. The first step in this process was to cluster 

the universe of medical diagnoses into broad, mutually exclusive categories. These groups were formed to be consistent in 

their anatomical or physiopathological classification, or in a 

manner in which they are clinically managed. Once these 

ajor diagnostic groups were formed, an interactive statistical 

gram (AUTOGROUP4) was used to fimther classify each 

ajor group into discrete DRG’s. This process incorporated 

patient information regarding diagnoses (primary and secondary), 

procedures, sex, and age to explain maximally a patient’s length 

of stay. In all, there currently are 470 DRG’s. 

Prospective reimbursement was authorized under the Tax 

Equity and Fiscal Responsibility Act of 1983. Under this act 

hospitals participating in the Medicare program were brought 

into this system beginning with their fiscal year as of October 

1, 1983. The Health Care Financing Administration, which 

operates the Medicare program, is allowing several years for 

hospitals to make a transition to prospective reimbursement by 

adjusting DRG payments based on certain hospital characteristics and geographic location. At the end of this phase-in period, 

care provided to a Medicare inpatient will translate into a preestablished payment based solely on the patient’s DRG. 

There is an important issue related to the NHDS and the 

implementation of this prospective reimbursement system how 

this system may affect the selection of a patient’s principal diagnosis andlor comorbidities. Because the NHDS is designed to 

collect data on the morbidity of the hospital inpatient population, any external influence on diagnostic practices may affect 

NHDS data. For example, two patients admitted to a hospital 

for treatment of chest pain-one diagnosed as having chest 

pain and the other diagnosed as having angina-will be placed 

into different DRG’s and have different reimbursement rates. 

There is speculation that in cases such as this prospective rehnbursement may influence the selection of a diagnosis,3 which in 

turn may affect estimates produced ffom the NHDS. After 

prospective payment has been in place for a few years, it may 

be possible to examine trends in NHDS data and determine 

the magnitude, if any, of this type of effect. 

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 shofi-stay non-Federal general and 

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

The sample for 1982 contained approximately 214,000 medical 

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

@

2 admncedata 

records from 426 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 NHDS data thereby could be used to prcduce national estimates of DRG’s. These estimates maybe of 

value for hospitals to compare their experience with that of 

other hospitals. For this reason, statistics in this report are 

frequency estimates 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 years of age and older. This 

allows a comparison with the Medicare population because 

Medicare covers most hospital costs for approximately 94 pe -

cent of discharges 65 years of age and over. Tables 1 an 

provide regional data, while tables 3 and 4 provide bed-s e data for these DRGs. 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 definition, some DRG’s are only for patients in a specific age range. In such a case the DRG title and the table title 

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

is, the most restrictive case of either the table or DRG title 

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 

Table 1. Number of discharges and averqge length of stay of patients under 65 years of age discharged from short-stay hospitals, by selected 

diagnosis-related groups and geographic regions: United States, 1982 

[Discharges 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 . . . . . . . . . . . . . . . . . . . . . . Llta Yo 3,304 I,ada Y,UU4 4,clYu 5.9 6.5 6.3 5.6 

Vaginal delivery without complicating 

diagnoses . . . . . . . . . . . . . . . . . . . . . . . . 

Medical back problems . . . . . . . . . 

Esophagitis, gastroenteritis, and 

miscellaneous digestive disorders, 

age 18-69 years without substantial 

comorbidity and/or complication. . . 

Cesarean section without substantial 

comorbidity and/or complication. . . . . . 

Nonradical hysterectomy, age less than 

70 years without substantial comorbidity 

and/or complication . . . . . . . . . . . . . . . . 

Unrelated operating room procedures. . . 

Esophagitis, gastroenteritis, and 

miscellaneous digestive disorders, 

age 0–17 years . . . . . . . . . . . . . .. . . . . . . . 

Psychoses . . . . . . . . . . . . . . . . . . . . . . 

Alcohol- and substance-induced organic 

mental syndrome . . . . . . . . . . . . . 

Dilation and curettage of uterus; 

ionization except for malignancy . . . . . . 

Abortion with dilation and curettage 

of uterus . . . . . . . . . . . . . . . . . . . . . 

Bronchitis and asthma, age O-1 7 years. .


Simple pneumonia and pleurisy, age


O-17 years . . . . . . . . . . . . . . . . . . . . . . . .


Tonsillectomy and/or adenoidectomy,


age 0–17 years . . . . . . . . . . . . . . . . . . . . .


Inguinal and femoral hernia procedures,


age 18–69 years without substantial


comorbidity and/or complication. . .


Diabetes, age greater than 35 years . . . .


Vaginal delivety with sterilization


and/or dilation and curettage of


uterus . . . . . . . . . . . . . . . . . . . . . . . . . . . .


Other factors influencing health status


Total cholecystectomy with common


bile duct exploration, age less than


70 years without substantial comorbidity


and/or complicatiorr . . . . . . . .


Bronchitis and asthma, age 18-69 years


without substantial comorbidity


andlor complication . . . . . . . . . . . . . . . .


2,784 524 765 937 559 2.9 3.4 3.3 2.7 2.2 

790 121 245 298 125 7.2 9.0 7.3 6.8 

m 

673 97 178 320 78 4.1 4.5 4.2 4.2 3.3 

649 125 145 258 121 5.7 6.7 6.2 5.3 4.8 

495 70 128 212 85 7.2 7.9 7.6 7.1 6.2 

401 75 116 145 65 11.2 13.8 12.0 9.7 10.1 

392 69 111 173 39 3.8 3.9 3.8 3.8 3.3 

388 95 118 108 68 16,5 19.1 19.7 13.8 11.6 

360 157 90 68 45 10.6 9.8 11.9 10.7 10.9 

345 111 85 118 32 1.8 1.7 1.9 2.0 1.2 

325 136 65 86 39 1.3 1.0 1.7 1.5 1.1 

313 65 96 118 34 3.9 4.6 3.8 3.8 3.3 

279 36 86 131 28 4.7 5.3 5.0 4.6 4.1 

279 43 106 83 48 1.8 1.7 1.9 2.1 1.2 

271 76 74 80 42 4.2 4.0 4.4 4.7 3.0 

259 52 72 104 30 8.2 9.9 8.7 7.4 6.4 

247 44 57 110 37 3.6 4.2 4.1 3.3 2.8 

242 53 68 75 46 3.5 3.6 3.8 3.2 3.4 

233 48 63 83 39 7.8 8.1 7.9 8.1 6. 

227 45 62 81 38 5.3 5.9 5.8 4.9 4.6 

5.0 
adwlncedata 3 

Table 2. Number of discharge and averaga length of stay of patients 65 years of age and over discharged from short-stay hospitals, by 

salected diagnosis- relatad groups and geographic regions: United States, 1982 

chargea 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 

Numbers in thousands Avaraae Ienath of stav in davs 

Alldischargas . . . . . . . . . . . . . . . . . . . . . . . 10,697 2,283 3,008 3,631 1,774 10.1 12.3 10.3 Y.4 8.2 

Lans procedures . . . . . . . . . . . . . . . . . . . . . 429 81 127 119 102 2.9 3.0 3.3 3.0 2.4 

Atherosclerosis, age greater than 

69 years and/or substantial comorbidity 

and complication . . . . . . . . . . . . . . . . . . . 427 99 109 157 62 8.7 10.9 9.0 8.2 6.3 

Heart failure and shock . . . . . . . . . . . . . . . . 387 88 108 132 59 9.7 11.8 10.3 8.8 7.7 

Esophagitis, gastroenteritis, and 

miscellaneous digestive disorders, 

age greater than 69 years and/or 

substantial comorbidity and 

complication . . . . . . . . . . . . . . . . . . . . . . . 376 63 102 169 42 6.7 8.3 6.9 6.3 5.8 

Chronic obstructive pulmonary disease. . . 300 54 76 117 54 9.8 11.9 10.2 8.8 9.2 

Specific cerebrovascular disordars 

axcept transient ischemic attack.. . . . . . 295 64 76 103 52 15.4 20.4 16.2 13.2 12.2 

Simple pneumonia and pleurisy, age 

greater than 69 yaars and/or substantial 

comorbidity and complication . . . . . . . . . 276 51 80 106 38 10.7 11.8 10.6 10.7 9.5 

Unrelated operating room procedures. . . . 226 59 65 72 29 17.3 20.0 17.5 15.8 15.0 

Diabetea, age greater than 36 yaars . . . . . 208 49 56 77 24 10.0 13.9 9.7 8.4 8.1 

Angina pectoris . . . . . . . . . . . . . . . . . . . . . . 195 49 47 67 32 6.6 8.0 6.4 6.6 4.9 

Medical back problems . . . . . . . . . . . . . . . 186 38 58 63 27 9.3 11.5 9.7 7.7 8.8 

Cardiac arrhythmia and conduction 

disorders, age greater than 69 years 

and/or substantial comorbidity 

and complication . . . . . . . . . . . . . . . . . . . 181 35 51 65 30 7.1 9.1 7.2 7.1 4.8 

Circulato~ disordera with acute 

yocardial infarction without 

rdiovascular complications, 

charged a live . . . . . . . . . . . . . . . . . . . . 174 44 44 62 24 12.2 13.6 12.9 11.8 9.4 

@ ypertension . . . . . . . . . . . . . . . . . . . . . . . . 158 28 43 70 17 7.9 8.8 7.7 7.6 8.4 

Transient ischemic attacks. . . . . . . . . . . . . 155 39 42 52 22 7.6 9.6 7.8 7.3 4.3 

Bronchitis and asthma, age greater than 

69 years and/or substantial comorbidity 

and complication . . . . . . . . . . . . . . . . . . . 148 22 38 59 29 8.3 9.2 8.0 8.3 8.0 

Transurethral prostatactomy, age greater 

than 69 years and/or substantial 

comorbidity and complication . . . . . . . . . 144 29 42 45 28 9.3 11.1 9.5 9.4 6.8 

Kidnay and urinary tract infections, 

agegreatar than 69 yaars and/or 

substantial comorbidity and 

complication . . . . . . . . . . . . . . . . . . . . . . . 142 23 34 67 17 8.5 9.9 8.8 8.1 7.1 

Respirato~ naoplasms. . . . . . . . . . . . . . . . 137 36 34 43 24 10.9 11.0 11.9 11.2 9.0 

Hip and femur procedures except 

major joint, agegreaterthan69 years 

and/or substantial comorbidity and 

complication . . . . . . . . . . . . . . . . . . . . . . . 135 27 45 38 25 19.5 25.1 19.9 18.5 14.3 

and/or substantial comorbidity and complication” in table 2 

would not include a patient under70 years of age because of 

the restriction in the DRG title. 

The most common DRG for patients under 65 years of 

age was “Vaginal delive~ without complicating diagnoses” 

(table 1), with an estimated 2.8 million discharges in 1982. 

“Cesarean section without substantial comorbidity and/or 

complication,” with 649,000 discharges, also was among the 

st frequent DRG’s in this age group. For patients 65 years 

ge and older (table 2), “Lens procedures” was the most 

a mmon DRG, 429,000, and “Atherosclerosis, age greater 

than 69 years and/or substantial comorbidity and complication:’ 

427,000, was 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 and North Central have the longest 

average length of stay and the West has the shortest. Regional 

length-of-stay differences were greater for patients 65 years of 

age or more than for younger patients. The West had an average 

length of stay of 5.0 days for patients under 65 years of age, 

and the Northeast had an average length of stay of 6.5 days, a 

difference of 1.5 days, or 30 percent greater. For older patients, 

however, the Northeast had an average length of stay 4.1 days 

greater than the elderly patients in the West (12.3 versus 8.2 

days), a difference of 50 percent. 

Overall there was 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 this pattern is not 
------ ---- ---- ---- ---- --- --- ---

4 acimncedata 

Table 3. Number of discharges and average length of stay of patients under 65 years of age discharged from short-stay hospitals, by selected 

diagnosis-related groups and hospital bed size United Ststes, 1982 

[Discharges from non-Federsl short-stay hospitals. Excludes newborn infants] 

500 5 

1oo- 2oo- 300- or 100- 200- 300- or 

All 6-99 199 299 399 more All 6-99 799 299 399 more 

Diagnosis-related group hospitals beds beds beds beds beds trospitels beds beds beds beds beds 

Number in thousands Aversge length of stay in days 

All discharges . . . . . . . . . . . . . . . z/,trY5 4,bti4 4,krLr6 4,493 b,YUY o, Y!JLr 5.9 4.5 3.s 5. I 0.2 O.ill 

Vaginal delive~ without 

complicating diagnoses. . . . . . 2,784 425 466 433 700 759 2.9 2.4 2.8 2.8 3.1 3.2 

Medicsl back problems . . . . . . 790 170 137 150 185 149 7.2 6.3 7.0 7.5 7.6 7.6 

Esophagitis, gastroenteritis, and 

miscellaneous digestive 

disorders, age 18-69 years 

without substantial comorbidity 

and/or complication . . . . . . . . . 673 191 116 115 143 108 4.1 3.3 4.3 4.6 4.2 4.8 

Cessrean section without 

substantial comorbidity and/or 

complication . . . . . . . . . . . . . . . 649 75 123 93 175 183 5.7 5.4 5.2 5.5 5.8 6.1 

Nonrsdicsi hysterectomy, age 

less thsn 70 years without 

substantial comorbidity and/or 

complication . . . . . . . . . . . . . . . 495 51 111 80 126 125 7.2 7.1 6.5 7.4 7.3 7.5 

Unrelated operating room 

procedures . . . . . . . . . . . . . . . . 401 50 65 65 98 123 11.2 6.9 7.7 12.8 13.0 12.5 

Esophagitis, gastroenteritis, and 

miscellaneous digestive 

disorders, age 0-17 . . . . . . . . . 392 82 97 60 78 75 3.8 2.7 3.7 3.8 4.0 4.8 

Psychoses . . . . . . . . . . . . . . . . . . 388 34 74 40 137 103 16.5 12.0 14.5 15.1 15.8 20.9 

Alcohol- and substance-induced 

organic mental syndrome . . . . . 360 105 59 39 97 60 10,6 9.6 13.5 12.9 9.9 9.4 

Dilation and curettage of uterus; 

conizstion except for 

malignancy . . . . . . . . . . . . . . . . 345 56 78 43 81 87 1.8 1.8 1.7 2.1 1.9 

Abortion with dilation and e 

curettage of uterus. . . . . . . . . . 325 36 68 41 78 102 1.3 1.6 1.4 1.5 1.2 1.1 

Bronchitis and asthms, age 

0–17 years . . . . . . . . . . . . . . . . 313 59 79 50 70 56 3.9 3.4 3.8 4.5 4.1 3.8 

Simple pneumonia and pleurisy, 

age O-17 years . . . . . . . . . . . . . 279 85 63 48 49 35 4.7 4.1 4.9 5.0 5.2 4.9 

Tonsillectomy snd/or 

sdenoidectomy, age O-17 

years . . . . . . . . . . . . . . . . . . . . . 279 52 55 63 68 41 1.8 1.6 1.8 1.9 1.7 1.9 

Inguinal snd femorsl hernia 

procedures, age 18-69 ysars 

without substantial comorbidity 

and/or complication. . . . . . . . . 271 40 50 45 72 64 4.2 4.2 3.9 4.4 4.2 4.2 

Diabetes, age greater than 

35 years . . . . . . . . . . . . . . . . . . 259 57 43 53 56 50 8.2 6.2 7.2 8.2 9.4 9.7 

Vaginal delive~ with 

sterilization and/ordination 

and curettage of uterus . . . 247 47 47 41 47 65 3.6 3.4 3.3 3.5 3.7 3.8 

Other fsctors influencing 

health status . . . . . . . . . . . . . . . 242 35 38 39 58 73 3.5 3.1 4.0 3.5 3.6 3.4 

Total cholecystectomy with 

common bile duct exploration, 

age less than 70 years without 

substantial comorbidity and/or 

complication . . . . . . . . . . . . . . . 233 44 41 34 65 48 7.8 7.2 7.5 8.4 8.4 7.4 

8ronchitis and asthma, age 

18-69 yesrs without 

substantial comorbidity and/or 

-. 

complication . . . . . . . . . . . . . . . 227 60 37 38 45 46 5.3 4.8 5.3 5.0 5.7 5.8 

consistent for some of the individual DRGs for which average 1–4) allows hospitals to compare their experience with tha 

length of stay in small and medium-size hospitals is equal to or other hospitals. Whale comparison is tenuous on a case-b@ 

greater than the average length of stay in large hospitals (500 case basis, a hospital with an average length of stay 2, 3, or 

or more beds). more days longer than the national average for a speciilc DRG 

The average length of stay associated with a DRG (tables may need to examine why it is so far from the norm. This kind 
aciuancedata 5 

Table 4. Number of discharges and average Iangth of stay of patienta 65 years of age or over discharged from short-stay hospitals, by selected 

diagnosis-related groups and hospital bed size United States, 1982 

‘Discharges from non-Federal short-stay hospitala. Excludas newborn infants] 

m 500 500 

1oo- 2oo- 300- or 100- 200– 300- or 

All 6-99 199 299 399 more All 6-99 199 299 399 more 

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

Number in thousands Average length of stay in days 

All discharges . . . . . . . . . . . . . . . 10,697 2,172 1,832 1,907 2,638 2,148 10.1 8.1 9.6 10.2 10.8 11.5 

Lens procedures . . . . . . . . . . . . . 429 32 94 85 118 99 2.9 2.9 3.0 2.6 3.0 3.1 

Atherosclerosis, age greater 

than 69 years and/or 

substantial comorbidity and 

complication . . . . . . . . . . . . . . . 427 90 87 80 107 63 8.7 7.3 8.1 8.8 9.6 10.2 

Heart failure and shock . . . . . . . 387 113 70 68 82 54 9.7 8.1 9.3 10.5 10.8 11.0 

Esophagitia, gastroenteritis, and 

miscellaneous digestive 

disorders, age greater than 

69 yeara and/or substantial 

comorbidity and 

complication . . . . . . . . . . . . . . . 376 123 60 64 78 51 6.7 5.6 7.2 6.9 8.3 6.5 

Chronic obstructive pulmonary 

disease . . . . . . . . . . . . . . . . . . . 300 76 48 58 71 48 9.8 8.1 9.5 0.7 10.6 10.5 

Specific cerebrovascular 

disorders except transient 

ischemic attack . . . . . . . . . . . . . 294 66 54 60 63 50 15.4 11.2 15.8 6.1 14.9 20.1 

Simple pneumonia and pleurisy, 

age greater than 69 years 

and/or substantial comorbidity 

and complication . . . . . . . . . . . 276 98 45 42 56 36 10.7 9.3 10.9 1.7 11.8 11.6 

Unrelated operating room 

procedures . . . . . . . . . . . . . . . . 226 29 42 45 58 52 17.3 14.1 17.3 6.0 17.5 19.9 

Diabetes, age greater than 

35 years . . . . . . . . . . . . . . . . . . 208 50 37 44 44 33 10.0 8.2 9.2 0.3 10.9 12.1 

Angina pectoris . . . . . . . . . . . . . . 195 54 34 40 44 23 6.6 5.9 6.3 6.3 7.6 7.4 

Medical back problems . . . . . . . 186 45 33 36 41 31 9.3 7.8 8.3 8.5 11.6 10.2 

Cardiac arrhythmia and 

conduction disorders, age 

greater than 69 years and/or 

substantial comorbidity and 

complication . . . . . . . . . . . . . . . 181 49 31 33 37 30 7.1 5.7 6.6 7.8 7.8 8.5 

Circulatory disorders with acute 

myocardial infarction without 

cardiovascular complications, 

discharged alive . . . . . . . . . . . . 174 35 27 31 46 35 12.2 11.2 11.6 12.1 12.9 12.9 

Hypertension . . . . . . . . . . . . . . . . 158 39 31 29 27 32 7.9 6.2 7.3 9.3 7.7 9.6 

Transient ischemic attacks . . . . 155 36 34 30 32 24 7.6 5.5 7.5 7.6 9.7 8.2 

Bronchitis and asthma, age 

greater than 69 years and/or 

substantial comorbidity and 

complication . . . . . . . . . . . . . . . 148 47 31 25 28 17 8.3 6.9 9.6 8.7 8.8 8.2 

Transurethra I prostatectomy, 

age greater than 69 years 

and/or substantial comorbidity 

and complication . . . . . . . . . . . 144 14 31 27 38 33 9.3 9.2 8.3 10.2 9.2 9.5 

Kidney and urinary tract 

infections, age graater than 

69 years and/or substantial 

comorbidity and 

complication . . . . . . . . . . . . . . . 142 48 26 20 31 18 8.5 7.2 9.2 8.5 9.2 9.4 

Respiratory neoplasms. . . . . . . . 137 22 19 19 40 37 10.9 7.7 10.8 10.0 11.8 12.4 

Hip and femur procedures 

except major joint, age greater 

than 69 years and/or 

substantial comorbidity and 

complication . . . . . . . . . . . . . . . 135 16 23 24 40 32 19.5 18.3 18.1 17.9 20.3 21.3 

�

0 of comparison may be worthwhile as a starting point, but even reimburse L ent is likely to affect areas such as-cost savings, 

within a DRG, average length of stay is not an exact measure quality of care, medical records keeping, and certain areas of 

of resource consumption. medical practice. However, for at least two reasons data curThe change to prospective payment for Medicare inpatient rently available on DRGs from the NHDS (this report and a 
6 

similar report using 1981 datal) should not be used to evaluate 

the success of prospective payment. First, the prospective payment program was not implemented until October 1983, and, 

second, historical trends must be studied to shed light on shortterm changes in hospital utilization. 

For example, from 1981 to 1982 average length of stay 

decreased 0.4 days for patients 65 years of age and over, and 

References 

1National Center for Health Statistics, R. Pokras: Diagnosis-related 

groups using data from the National Hospital Discharge Survey. United 

States, 1981. Advance Data From Vital and Health Statistics. 

No. 98. DHHS Pub. No. (PHS) 84– 1250. Public Health Service. 

Hyattsville, Md., July 20, 1984. 

zNational Center for Health Statistics, E. J. Graves: Utilization of 

short-stay hospitals, United States, 1982 Annual Summary. Vital and 

Health Statistics. Series 13, No. 78. DHHS Pub. No. (PHS) 84-

1739. Public Health Service. Washington. U.S. Government Printing 

Office, Aug. 1984. 

3J Alsofrom: Playing the numbers. Medical World News, Oct. 24, 

1983, pp. 38-55. 

4R. 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 permission of Medical Care. ) 

5Nationa] center for Hea]th Statistics, W. F. Lewis: Utilization of 

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

1972. Vita/ and Health Statistics. Series 13, No. 19. DHEW Pub. 

No. (HR4) 75–1 770. Health Resources Administration. Washington. 

U.S. Government Printing Otlice, June 1975. 

6Nat1unal Center for Health Statistics, M. G. Sirken: Utilization of 

short-stay hospitals, summary of nonmedical statistics, [ Tnited States, 

Technical notes 

Survey methodology 

Source of data 

The National Hospital Discharge Survey (NHDS) encompasses patients discharged from short-stay hospitals, exclusive of military and Veterans Administration hospitals, 

located in the 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 1982 consisted of 550 hospitals. Of these, 71 refused 

to participate and 53 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 426 hospitals particisome specific DRGs also showed a reduction in average length 

of stay. However, length of stay in short-stay non-Federal hospitals has been decreasing for over a decade (the average length 

of stay for patients 65 years of age and over was 12.2 days in 

19725 compared with 10.1 days in 1982), and it will take more 

time to understand the effects prospective payment will have, if 

any, on hospital utilization. 

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

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

Printing Oflice, Aug. 1967. 

TNationa] Center for Health Statistics, M. J. Witkin: Utilization of 

short-stay hospitals by characteristics of discharged patients, United 

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

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

Printing Oflice, Dec. 1967. 

sNational Center for Health Statistics, R. Pokras: Surgical and nonsurgical 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 Oflice, Feb. 1983. 

9U s, public Hea]th Semite and Health Care Financing Administration: International CIass@cation ofDiseases, 9th Revision, Clinical 

Modification. DHHS Pub. No. (PHS) 80–1 260. Public Health Service. Washington. U.S. Government Printing OffIce, Sept. 1980. 

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

Sept. 1, 1983. 

pated in the survey during 1982 and provided approximately 

214,000 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 hopsitals 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 

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 
7


‘r 

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

selecting sample discharges varied inversely with the probability 

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 discharge 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.6,7 

Diagnosis-related groups 

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

were produced using the most current DRG program available 

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

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

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

Support Group, 100 Broadway, New Haven, Corm. 065 11). 

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:g,g 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, 1983.10 

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 

Sampling errors and rounding of numbers 

The standard error is a measure of the sampling variability 

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

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 firstlisted diagnoses for 1982. 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 tvotailed Bonferroni test for multiple comparisons. 

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

indicate that the differences are statistically significant. Terms 

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

significant 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 

short-stay hospitals. 

Table 1. Approximate ralative standard errors of estimated number 

of discharges and first-listed diagnoses: United States, 1982 

Relative 

standard 

Size of estimate error 

10,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.3 

50,000........................................ 10.2 

100,000,.,.......,...,......,.. .. ............ 8.5


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


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


1,000,000
..................................... 5.1


4,000,000..,,.......,,...,.,,..
 ............... 4,0


Tabla i1. Approximate standard errors of average lengths of stay 

by number of discharges: Unitad States, 1982 

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 . .


r	 data, and any similarity between the titles of those categories 

and DRG titles is coincidental. 

NOTE: A list of references follows the text. 

I 
8 acklnceckta 

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 admission 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 Island, Connecticut, 

New York, New Jersey, and Pennsylvania 

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

Dakota, South Dakota, Nebraska, and 

Kansas 

Region—Con. States included—Con. 

South . . . . . . . . . Delaware, Ma@and, District of Columbia, 

Virginia, West Virginia, North Carolina, 

South Carolina, Georgia, Florida, Ken- e 

tucky, Tennessee, Alabama, Mississippi, 

Arkansas, Louisiana, Oklahoma, and 

Texas 

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

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

Alaska 

Hospitals—Short-stay special and general hospitals have 

six beds or more for inpatient use and an average length of stay 

of less than 30 days. Federal hospitals and hospital units of 

institutions are not included. 

Bed size of hospital—Size is measured by the number of 

beds, cribs, and pediatric bassinets regularly maintained (set 

up and staffed for use) for patienty bassinets for newborn infants 

are not included. In this report the classification of hospitals by 

bed size is based on the number of beds at or near midyear 

reported by the hospitals. 

) 

Recent Issues of Advance Data From Vital and Health Statistics 

No. 104. Fecundity and Infertility in the United States, 1965-82 (In No. 101. 1983Summary National Hospital Discharge Survey (Ispreparation) ~ued Sept. 28, 1984) 

No. 103. Use of Services for Family P1aming and Infertility: United No. 100. CAT Scan Use in Short-Stay Non-Federal Hospitals: 

States, 1982 (Issued Dec. 20, 1984) United States, 1979-82 (Issued Sept. 28, 1984)


No. 102. Use of Contraception in the United States: 1982 (Issued �


Dec. 4, 1984) 

Suggested Citation 

National Center for Health Statistics, R, Pokras 

and K. K. Kubishke: Diagnosis-Related Groups 

Using Data From the National Hospital Discharge 

Survey, United States, 1982. Advance Data From 

Vital and Hea/th Statistics. No. 105.DH HS Pub. 

No. (PHS) 85-1250. Public Health Service, 

Hyattsville, Md., Jan. 18, 1985. 

U.S. DEPARTMENT OF HEALTH AND 

HUMAN SERVICES 

Public Health Service 

National Center for Health Statistics 

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Hyattsville, Maryland 20782 

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