From Vital and Health Statistics of the National Center for Health Statistics September 28, 1984 � Number 100 

PROPERW OF W? 

PUBLICATIONS%?ANCh 

EDfTORfAL LUNIARY 

CAT Scan Use in Short-Stay Non-Federal Hospitals: 

United States, 1979-82 

by Edmund J. Graves, Division of Health Care Statistics 

* 

a 

This report presents statistics on the use of computerized 

axial tomography scans by inpatients during the period 1979– 

82. The age and sex of the patients who received these scans, 

their diagnoses, the types of scans they received, and the expected sources of payment for the scans are shown. In addition, 

“ ormation on the hospitals in which the scans were performed 

eporte~ including the geographic region, size, and ownership 

the facility. Hospital use measurements include frequencies, 

percent distributions, and population-based rates. 

The statistics presented in this report are based on data 

collected by means of the National Hospital Discharge Survey, 

a continuous survey that has been conducted by the National 

Center for Health Statistics since 1965. Statistics are presented 

for discharges from 1979 through 1982. In each of these years 

data were abstracted from the face sheets of medical records of 

approximately 220,000 patients discharged from over 400 

shoti-stay non-Federal hospitals. A brief description of the 

sample design, data collection and estimation procedures, and 

deftition of terms used in tis report can be found in the section 

entitled “Technical notes.” A detailed discussion of these items 

and the survey form used to collect the data have been published. 1’2 

The coding of medical data for hospitalized patients is 

done according to the International ClasslYcation of Diseases, 

9th Revision, Clinical Modl@cation (ICD–9–CM).3 

Background of CAT scans 

A computerized axial tomography (CAT) scanner is a 

radiographic device that combines the technologies of radiology, 

computer processing, and cathode ray tube (CRT) display. This 

biographic device produces an image of the transverse section 

the bcdy part in question. The image resembles an anatomic 

ction.4 Tomography is defined as a technique of X-ray 

photography by which a single plane is photographed, with the 

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES 

outlines of structures in other planes eliminated.5 Computerized 

tomography, also known as computerized axial tomography 

and computerized transverse axial tomography, has been 

rapidly accepted by the American medical community since its 

development in 1970.6 The number of CAT scanners in use# 

hospitals in the United States has grown horn a mere handful 

in 1973, when the technique was introduced in the United 

States, to 1,716 in 1982.7 The principles underlying CAT were 

first elucidated in 1961, and 11 years later the first scanner 

(designed by G. H. Hounstield, a researcher with the British 

firm EMI, Ltd.s) became available.g~lo 

Clinical applications and historical 

background of CAT scanners 

The CAT scanner can depict various intracranial or intraabdominal abnormalities that previously might have required 

invasive procedures or surgical exploration. CAT scans can 

generally identify space-occupying lesions of the brain, such as 

tumors, hematomas, cysts, cerebral infarcts, hemorrhagic 

changes, calciilcation, metastatic disease, and hydrocephalus. 

Body scanners enable technicians to evaluate extensive abnormalities in the liver, retroperitoneal area, pancreas, bladder 

and related structures, and ether pelvic structures.4 

The major advantage of CAT scanning lies in its ability to 

provide clear radiographic definition of structures not visible 

by other techniques. It is a noninvasive procedure without signiilcant risk, morbidity, or discomfort. The quality of CAT 

scans may be improved if used in conjunction with a dye that 

produces clearer images, especially of tumors. A disadvantage 

of the early units was the relatively slow scan time, which not 

only resulted in image degradation but also necessitated relatively long exposure to radiation. New scanners have been 

developed that can scan in 5 seconds or less. Motion, which 

once caused image degradation, is no longer a serious tecluical 

. 

Public Health Service 
2 

limitation. Scanners that will evaluate cardiac function in a 

matter of milliseconds are being developed.4 

The CAT scan provides surgeons with a long-sought 

method for better diagnosing of low back pain. It can spot spinal 

anomalies that were missed by the myelogram and by the operating surgeon. It has been reported by one hospital that the 

success rate for certain back surgeries has increased from 5 to 

80 percent, with most of the credit for the success rate increase 

given to CAT scans. *1The CAT scan is now used in conjunction with the position emission tomography (PET) scanner to 

provide an accurate diagnosis of Alzheimer’s disease without 

extensive testing.l 2 

The data presented in the National Hospital Discharge 

Survey have shown a tremendous increase in inpatient use from 

1979 through 1982. In spite of the rapid growth of this technology, there are some drawbacks to the use of the CAT scanner. 

First, a CAT scanner is expensive. In 1974 the cost of a scanner 

was $300,000. By 1980 this cost had risen to $700,000. This 

increase was offset partially by the efficiency of the newer 

models. 13Second, the cost to the patient is hig~ the cost of one 

scan was approximately $250 in 1980.14 A thhd drawback is 

the exposure to radiation. This is a serious deterrent, despite 

the faster scanning time of new equipment, and limits the number 

of CAT scans that can be performed on a patient in any one 

year. Because of concern with the cost and appropriate supply 

and distribution of this expensive technology, the national health 

planning program promulgated standards for the purchase and 

use of CAT scanners. These standards were included in the 

“National guidelines for health planning,” which were published 

in March 1978.15 Health planning agencies were to use the 

standards as benchmarks against which to assess local conditions and needs. The agencies’ assessments, based on these 

standards, determined whether a certificate of need was granted 

to allow purchase of new or additional equipment. 

The standards published in 1978 were as follows: (1) A 

CAT scanner (head and body) should operate (for the second 

and subsequent years of operation) at a minimum of 2,500 

medically necessary patient procedures per year, and (2) no 

additional scanners should be approved unless each scanner in 

the health service area is performing at a rate greater than 2,500 

medically necessary patient procedures per year. 

These standards were in effect until November 1982. At 

that time, the Department of Health and Human Services rescinded the CAT standard from the “National guidelines for 

health planning.” 16 It was decided that the standard did not 

adequately take into account recent advances in scanner technology. State health planning agencies remain free to develop 

their own standards for review of certificate-of-need applications to purchase CAT scanners. 

The CAT scanner may eventually be supplanted by equip 

ment that has broader capabilities. These are the positron emission tomography (PET) scannerl 7 and the nuclear magnetic 

resonance (NMR) scanner. 18 The latter uses a magnetic field, 

thus avoiding radiation altogether. Unlike the CAT scanner, 

which only shows the size of tumor, stroke damage, and so 

forth, NMR equipment reveals anatomical changes (by examining the chemical and metabolic functioning of organs) that 

indicate not only current problems but problems that may occur 

in the fhture. For example, the NMR scanner reveals the sodium 

content of brain cells, which aids in ascertaining the extent 

stroke damage. The Food and Drug Administration has recen 

given its approval for the use of the NMR scanner, which maker 

its use eligible for patient insurance coverage. 

Highlights 

�	 The number of CAT scan procedures performed in shortstay hospitals during the period 1979 through 1982 has 

tripled (from 194,000 to 600,000). 

�	 Approximately 40 percent of all CAT scans performed in 

short-stay hospitals during the period 1979 through 1982 

were performed on patients 65 years of age and over. 

�	 Of the patients who had CAT scans performed, approximately 42 percent expected medicare to pay for them and 

approximately 39 percent expected private insurance to 

pay for them. 

�	 Over 25 percent of all CAT scans performed during the 

period were in the Middle AtJantic Division. However, the 

West North Central Division had a higher rate of procedures per 10,000 population than the Middle Atlantic 

Division did. 

�	 Over 40 percent of all CAT scans performed in short-stay 

hospitals during the period 1979– 1982 were performed in 

hospitals having 500 beds or more. 

�	 About 75 percent of all CAT scans done in short-stay 

hospitals in the period 1979 through 1982 were done o 

nonprofit hospitals. 

�	 About 60 percent of all CAT scans performed in shortstay hospitals during the period 1979 through 1982 were 

performed on the head. 

Sex and age of patient 

The estimated number of CAT scans performed on inpatients in short-stay non-Federal hospitals has risen from 

approximately 194,000 in 1979 to 600,000 in 1982: an increase of about 200 percent (table 1). It should be emphasized 

that these scans are for inpatients only there are a considerable 

number of CAT scans performed in outpatient departments, 

medical clinics, and mobile units. Outpatient departments have 

the use of in-house scanners if time is available. In addition, 

19 percent of all CAT scanners in use have been purchased by 

hospital outpatient departments and doctor’s off~ces.l 9 

The rate of CAT scans per 10,000 population ranged from 

8.6 to 26.0 for mrdes during this period while the rate for females 

ranged from 8.8 to 26,1 for the same period. Although the rates 

increased over time for each sex, the rates between the sexes 

showed no significant differences. The number and rate of procedures per 10,000 population by age is smallest for those under 

15 years of age and largest for those 65 years of age and over. 

Rates per 10,000 population for those under 15 years of ag~ 

ranged from 3.5 to 8.5 during the period 1979-1982, while fC 

those 65 years and over they ranged from 26.5 to 92.5. Ap ~ 

proximately 40 percent of the CAT scans performed on patients 

were performed on those 65 years of age and over, while only 8 

percent were performed on those under 15 years of age. Varia-
dmcec=J3 

Table 1. Numbar, rata, and parcent distribution of CAT scans for patients discharged from short-stay non-Faderal hospitals by sex and age: 

~nited States, 1979-82 

I Sex and age 1979 1980 1981 1982 1979 1980 1981 1982 1979 1980 1981 1982 

Number in thousands Rate per 10,000 population Percent 

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 306 424 600 8.7 13.6 18.6 26.1 100.0 100.0 100.0 100.0 

Sex 

Male, ,, . . . . . . . . . . . . . . . . . . . . . . 93 152 205 289 8.6 13.9 18.7 26.0 47.9 49,5 48.4 48.2 

Female, , . . . . . . . . . . . . . . . . . . . . . 101 154 219 311 8.8 13.2 18.6 26.1 52.1 50.5 51.6 51.8 

Age 

Less than 15 years . . . . . . . . . . . . . . . . 18 27 34 44 3.5 5.3 6.6 8.5 9.2 8.9 8.0 7.3 

15-44 years . . . . . . . . . . . . . . . . . . . . . 54 74 103 150 5.3 7.1 9.8 14.0 28.1 24.1 24.3 25.0 

45-65 years . . . . . . . . . . . . . . . . . . . . 55 65 114 158 12.4 19.0 25.6 35.6 28.3 27.7 26.8 26.4 

65 years and over . . . . . . . . . . . . . . . . 67 120 173 246 26.5 46.7 66.0 92.5 34.4 39.3 40.9 41.4 

tions in the percent distribution by age showed no significant 

difference from year to year. 

Source of payment 

Medicare, which is primarily for those 65 years of age and 

over, was the expected source of payment for approximately 

42 percent of all CAT scans performed in short-stay nonFederal hospitals between the years 1979 and 1982, while 

~rivate insurance was the expected source of payment for about 

9 percent (table 2). Medicaid was the expected source of 

ayment for about 7 percent of the CAT scans, while other 

payments and self-pay accounted for about 5 percent each. 

Workmen’s compensation accounted for the remaining 2 percent. There was no significant difference in expected source of 

payment from year to year. 

Geographic division 

The Middle Atlantic Division recorded the largest number 

of CAT scan procedures (433,000) performed on patients during the period 197 9–82, while the Mountain Division recorded 

the smallest number of CAT scans about 30,000 (table 3). For 

most years rates per 10,000 population were highest in the 

West North Central Division and lowest in the West South 

Central and Mountain Divisions. In 1982 the rates ranged from 

Table 2. Number and percent distribution of CAT scans for patients discharged from short-stay non-Federal hospitals by expected source of 

payment: United Statea, 1979–82 

Expected source of payment 1979 1980 1981 1982 1979 1980 1981 1982 

Number in thousands Percent 

All sources.........,......,.. . . . . . . . . . . . . 194 306 424 600 100.0 100.0 100.0 100.0 

Blue Cross and other private insurance . . . . . . . . 76 124 161 239 39.1 40.4 38.1 39.9 

Medicare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 129 184 261 35.5 42.0 43.4 43.5 

Medicaid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 21 29 37 6.6 6.B 6.9 6.1 

Self-pay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Workmen’s compensation . . . . . . . . . . . . . . . . 

11 

* 17 

* 21 

11 

29 

16 

5.9 * 5.6 * 5.0 

2.5 

4.8 

2.7 

Other paymenta . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 13 17 17 12.2 4.1 4,0 2.9 

Table 3. Number, rate, and percent distribution of CAT scans for patients discharged from short-stay non-Federal hospitals by geographic 

divisions: United States, 1979-82 

Geographic division 1979 1980 1981 1982 1979 1980 1981 1982 1979 1980 1981 1982 

Number in thousands Rate per 10,000 population Percent 

All divisions . . . . . . . . . . . . . . . . . . . . . . 194 306 424 600 8.7 13.6 18.6 26.1 100.0 100.0 100.0 100.0 

New England . . . . . . . . . . . . . . . . . . . . . . *5 11 17 27 *4.3 8.7 13.7 21.7 *2.B 3.5 4,0 4.5 

_+Aiddle Atlantic . . . . . . . . . . . . . . . . . . . 50 7B 117 18B 13.5 21.3 31.8 51.1 26.0 25.6 27.6 31.4 

ast North Central . . . . . . . . . . . . . . . 20 29 45 39 4.7 7.0 10.8 9.5 10.2 9.5 10.6 6.6 

1 dest North Central . . . . . . . . . . . . . 27 57 71 100 15.7 33.1 41,6 57.B 14.0 18.5 16.8 16.6 

South Atlantic . . . . . . . . . . . . . . . . . . . . 19 34 67 95 5.4 9.2 18.1 25.2 9.B 11.1 15.9 15.8 

Eaat South Central . . . . . . . . . . . . . . . *7 17 17 17 �4,7 11.4 11.8 11.5 *3.5 5.5 4.1 2.8 

West South Central . . . . . . . . . . . . . . . . . *7 *8 16 20 *3.1 *3.6 6.5 8.0 *3.6 *2.8 3.7 3.3 

Mountain . . . . . . . . . . . . . . . . . . . . . . . . * * *8 17** *6.5 6.6 * * *1.8 2.8 

Pacific . . . . . . . . . . . . . . . . . . . . . . . . . . 55 70 66 97 17,B 22,1 20.6 29.8 28.2 22.8 15.5 16.2 
4 admncedata 

6.6 per 10,000 population for the Mountain Division to 57.8 

per 10,000 population for the West North Central Division. 

The differences in the CAT scan rates could not be attributed 

to the age differences in the population. 

Size of hospital 

The number and percent of CAT scans performed during 

the period 1979-82 were lowest in hospitals with less than 100 

beds (3 percent in 1982) and largest in hospitals with more 

than 500 beds (39 percent in 1982) (table 4). In comparison, 

for all procedures, 11 percent were performed in hospitals with 

less than 100 beds and 29 percent in hospitals with more than 

500 beds. One possible reason for the small number of CAT 

scan procedures performed in the smallest hospitals may be 

that CAT seamers are quite expensive and require trained personnel to operate them. Small hospitals often do not have the 

resources in personnel or finances to purchase and operate them. 

The standards in the “National guidelines for health planning,” which were in effect until November 1982,15’16also 

tended to discourage smaller hospitals from purchasing this 

equipment. The target of 2,500 patient procedures per year for 

efficient utilization requires a larger patient population than is 

available in many smaller hospitals. 

Hospital ownership 

During the period 1979-82, 1,141,000 CAT sc 

(75 percent) were performed in nonprofit hospitals; 321,00 @ ‘

(21 percent) were performed in State or local government 

hospitals; the remaining 4 percent were performed in proprietary 

hospitals (table 5). Within the 4 years there was no significant 

shift by hospital ownership in the percent of CAT scans performed. 

Anatomical site 

Of the 1,524,000 CAT scans performed during the period 

1979-82,921,000 (60 percent) were scans of the head (table 6). 

This is not surprising because head scanners were the first scanners introduced, and the head is the area of the body where this 

type of noninvasive procedure is most useful. Head scans are 

used to determine the extent of brain tumors and whether they 

are operable, and the extent of stroke damage to ascertain the 

feasibility of cleaning up the stroke debris. The other area of the 

body where CAT scanning is quite common is the abdomen. 

There were 180,000 (12 percent) performed on the abdomen. 

Of the 600,000 CAT scans performed during 1982, 

359,000 were scans of the head (table 7). Of these 359,000 

Table 4. Number and percent distribution of CAT scans for patients discharged from short-stay non-Federal hospitals by bed size: United States, 

1979-82 

Bed size 1979 1980 7987 1982 1979 1980 1981 79 

Number in thousands Percent 

All sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 306 424 600 100.0 100.0 100.0 100,0 

* * 6–99 beds . . . . . . . . . . . . . . . . . . . . . . . . . . . *7 18 16 *2.2 4.4 2.7 

100-199 beds . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 53 63 93 1&6 17.2 14.8 15.6 

200-299 beds . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 30 51 98 10.3 9.9 12.0 16.4 

300-499 beds . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 73 107 158 26.4 23.7 25.2 26.4 

5000r more beds..........,,. . . . . . . . . . . . . 90 144 185 234 46.2 47.0 43.6 39.0 

Table 5. Number and percent distribution of CAT scans for patients discharged from short-stay non-Federal hospitals by type of ownership: 

United States, 1979-82 

Type of ownership 1979 1980 1981 1982 1979 1980 1981 1982 

Number in thousands Percent 

All hospitals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 306 424 600 100.0 100.0 100.0 100.0 

Nonprofit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 228 306 467 72.2 74.5 72.0 77.8 

Proprietary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 15 16 21 5.0 4.9 3.8 3.6 

State andlocal government . . . . . . . . . . . . . . . . . 44 63 102 112 22.8 20.7 24.1 18.6 

Table 6. Number, rate, and percent distribution of CAT scans by site of scan for patients discharged from short-stay non-Federal hospitals: 

United States, 1979-82 

Site of CA T scan 1979 1980 1981 1982 1979 1980 1981 1982 1979 1980 1981 1982 

Number in thousands Rate per 10,000 population Percent distribution 

All CAT scans . . . . . . . . . . . . . . . . . . . . . . 194 306 424 600 8.7 13.6 18.6 26.1 100.0 100.0 100.0 100. 

Head . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 190 266 359 4.7 8.4 11.7 15.6 54.6 62.1 62.7 59.8 

Abdomen . . . . . . . . . . . . . . . . . . . . . . . . . 15 32 56 77 0.7 1.4 2.4 3.4 7.7 10.5 13.2 12.8 

Other specified . . . . . . . . . . . . . . . . . . .,, * *8 11 23 * “0.3 0.5 1.0 * *2.6 2.6 3.8 

Other unspecified . . . . . . . . . . . . . . . ... 69 75 91 141 3.1 3.3 4.0 6.1 35.6 24.5 21.5 23.5 
---

admcdaa5 

Table 7. Number and percent of CAT scans, by sites of scans and 

principal diagnoses for patients discharged from short-stay 

on-Federal hospitals: United States, 1982 

Site of CA T scan and diaanosis and Number in 

ICD-9-CM cod; 1 thousands Percent 

All head scans . . . . . . . . . . . . . . . . . . . . . . . . . . 359 100.0 

Cerebrovaacular disease. . . . . . . ...400-438 82 22.9 

Malignant neoplasm . . . . . . . . . . ...140-208 29 8.1 

Concussion and intracranial injury. .. 850-854 23 6.5 

Heart disease . . . . . . . . . . . . . . . . . .391-392,, 

393-398,402,404,410, 416,420-429 20 5.6 

All abdomen scans . . . . . . . . . . . . . . . . . . . . . . 77 100.0 

Malignant neoplaam . . . . . . . . . . ...140-208 20 26.2 

lU.S. Public Health Sewice and Health Care Financing Administration: 

International Classification of Diseases, 9th Revision, Clinical Modification. 

DHHS Pub. No. (PHS} 80-1260. Public Health Sewice. Washington. U.S. 

Government Printing Office, Sept. 1980. 

head scans, 82,000 were for cerebrovascular disease, 29,000 

were for malignant neoplasm, 23,000 were for concussion and 

intracranial injury, and 20,000 were for heart disease. The other 

anatomical site where there were signii3cant numbers of scans 

was the abdomen. There were 77,000 scans of the abdomen 

during 1982, and, of these, 20,000 were for suspected neoplasm. 

Diagnosis 

The two leading diagnostic groups for which CAT scans 

ere performed were circulatory diseases (150,000 or 25 percent) and neoplasms (82,000 or 14 percent) (table 8). 

“Ofthe 150,000 CAT scans pe~ormed on the circulatory 

system, 96,000, or 64 percent, were performed for cerebrovascular disease; of the 82,000 CAT scans performed because 

of suspected neoplasms, 71,000 or 86 percent were for suspected malignancy. Other leading diagnoses were injury and 

poisoning (68,000) and diseases of the nervous system and 

sense organs (60,000). 

Table 8. Number and percent distribution of CAT scans by all-iistad 

diagnosea and ICD–9–CM codes for patients discharged from 

short-stay non-Federal hospitals: United States, 1982 

Number in Percent 

Diagnosis and ICD-9-CM codel thousands distribution 

All CATscans . . . . . . . . . . . . . . . . . . . . . . . 

Infectious and parasitic 

diseases. . . . . . . . . . . . . . . . ...001-139 

Neoplasms . . . . . . . . . . . . . . ...140-239 

Endocrine, nutritional, and metabolic 

diseases and immunity 

disorders . . . . . . . . . . . . . . . . . . 240-279 

Diseases of the blood and blood-forming 

organs . . . . . . . . . . . . . . . . . . .. 280-289 

Mental disorders. . . . . . . . . . ...290-319 

Diseases of the nervous system and 

aense organs . . . . . . . . . . . . . . .320-389 

Diseases of the circulato~ 

system . . . . . . . . . . . . . . . . . . .. 390-459 

Diseases of the respiratory 

system . . . . . . . . . . . . . . . . . . .. 460-519 

Diseases of the digestive 

system . . . . . . . . . . . . . . . . . . . .520-579 

Diseases of the genitourinary 

system . . . . . . . . . . . . . . . . . . . .580-629 

Complications of pregnancy, childbirth, 

and the puerperium . . . . . . ...630-676 

Diseases of the skin and subcutaneous 

tissue . . . . . . . . . . . . . . . . . . . . .680–709 

Diseases of the musculoskeletal 

system . . . . . . . . . . . . . . . . . . . .710-739 

Congenital anomalies. . . . . . ...740-759 

Certain conditions originating in the 

perinatal period. . . . . . . . . . . . . 760–779 

Symptoms, signs, and ill-definad 

conditions . . . . . . . . . . . . . . . ..780–799 

Injwy and poisoning. . . . . . . ...800-899 

Supplementary classifications. . . VOI -V82 

600 100.0 

12 2.1 

82 13.7 

22 3.7 

*5 “0.9 

40 6.7 

60 10,0 

150 24.9 

19 3.1 

39 6.5 

16 2.7 

* * 

* * 

50 8.4 

*7 *1.1 

* * 

20 3.3 

68 11.3 

*5 “0.9 

1U.S. Public Health Service and Health Care Financing Adminiatration: 

International Classification of Diseases, 9th Revision, Clinical Modification. 

DHHS Pub. No. (PHS) 80-1260. Public Health Service. Washington. U.S. 

Government Printing Office, Sept. 1980. 

* 

Symbols 

Data not available 

. . . Category not applicable 

0.0 

z 

* 

# 

Quantity zero 

Quantity more than zero but less than 

0.05 

Quantity more than zero but less than 

500 where numbers are rounded to 

thousands 

Figure does not meet standards of 

reliability or precision 

Figure suppressed to comply with 

confidentiality requirements 
6 

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

Office, Aug. 1967. 

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

short-stay hospitals by characteristics of discharged patients, United T 

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

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

Printing 0f17ce, Dec. 1967. 

Recent Issues of Advance Data From Vital and Health Statistics 

No. 99. Health Care of Adolescents by Oftice-Based Physicians: No. 96. Utilization of Analgesic Drugs in Otlice-Based Ambulatory 

National Ambulatory Medical Care Survey, 1980–8 1 (Issued Sept. Care: National Ambulatory Medical Care Survey, 1980-81 (Issued 

1984) March 14, 1984) 

No. 98. Diagnosis-related groups using data from the National No. 95. 1982 Summary: National Hospital Discharge Survey (IsHospital Discharge Survey: United States, 1981 (Issued July 20, sued December 27, 1983) r 1984) 

No. 97. The Management of New Pain in 013ice-Based Ambulatory 

Care: National Ambulatory Medical Care Survey, 1980 and 1981 

(Issued June 13, 1984) 
--

Technical notes 

4--” 

;ource 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 shofi-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, 1979, and 1981. 

In all, 550 hospitals were sampled in 1982. Of these hospitals, 

71 refused to participate, and 53 were out of scope. The 426 

participating hospitals 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 hospitals was 

,d---‘made through a controlled selection technique so that hospitals 

.1the 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 

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 

and procedures 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 or 

procedures were entered on the face sheet of the medical record. 

/ Statistics produced by the NHDS are derived by a complex 

stimating procedure. The basic unit of estimation is the sample 

.npatient discharge abstract. The estimating procedure used to 

produce essentially unbiased national estimates in the NHDS 

has three principal components: inflation by reciprocals of the 

probabilities of sample selection, adjustment for nonresponse, 

dmcdata7 

and ratio adjustment to fixed totals. These components of estimation are described in appendix I of two earlier publications.20’2 1 

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 an 

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. Relative 

standard errors for procedures are shown in table I. 

Estimates have been rounded to the nearest thousand. For 

this reason detailed figures within tables do not always add to 

the totals. Rates and average lengths of stay were calculated 

from original unrounded figures and $vill not necessarily agree 

precisely with rates or average lengths of stay calculated from 

rounded data. 

Tests of significance 

In this report, the determination of statistical inference is 

based on the tw~tailed 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 

Hospitals and hospital characteristics 

Hospitals—Short-stay special and general hospitals have 

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

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

institutions are not included. 

Table 1. Approximate relativa standard errors of estimated numbers 

of all-listed procedural: United Stataa, 1982 

Relative standard 

Size of estimate error 

5,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.4 

10,000
 ............................. .. 13.7


25,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.5 

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


100,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2 

500,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 

1,000,000............................. 6.8 

3,000,000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 

5,000,000............................ 5.8 

10,000,000....................... .. . 5.4 

15,000,000. .. . . . . . . . . . . . . . . . . . . . . . . . . 5.2 

20,000,000. . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 

25,000,000. . . . . . . . . . . . . . . . . . . . . . . . . . 5.0 

NOTE: A list of references follows the text. 
8 

Bed size of hospital—Measured by the number of beds, 

cribs, and pediatric bassinets regularly maintained (set up and 

staffed for use) for patients; bassinets for newborn infants are 

not included. In this report the classification of hospitals by 

bed size reported by the hospitals is based on the number of 

beds at or near midyear. 

Type of ownership of hospital—Determined by the organization that controls and operates the hospital. Hospitals are 

grouped as follows: 

. Voluntary nonproJ7t-Hospitals operated by a church or 

another nonprofit organization. 

. Government-Hospitals operated by a State or local government. 

. Proprietary-Hospitals operated by individuals, partnerships, or corporations for profit. 

Procedure—One or more surgical or nonsurgical operations, procedures, or special treatments assigned by the physician to patients discharged from the inpatient service of shortstay hospitals. In the NHDS all terms listed on the face sheet 

(summary sheet) of the medical record under the captions 

“operation,” “operative procedures,” “operations andlor 

special treatment,” and the like are transcribed in the order 

listed. A maximum of four procedures are coded. 

Rate ofprocedures—The ratio of the number of all-listed 

procedures during a year to the number of persons in the civilian 

population on July 1 of that year. . 

Suggested Citation 

National Center for Health Statistics, E. J. Graves: 

CAT scan use in short-stay non-Federal hospitals, 

United States, 1979-82. Advance Data From 

Vital and Health Statistics, No. 100. DH HS Pub. 

No. (PHS) 84-1250. Public Health Service. 

Hyattsville, Md., Sept. 28, 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 BUSINESS


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Demographic terms 

Age—Refers to the age of the patient on the birthday prior 

to admission to the hospital inpatient service. o Census division—One of the mine geographic divisions of 

the United States corresponding to those used by the Bureau of 

the Census: 

Division 

New England . . . . . . . . 

Middle Atlantic . . . . . . 

South Atlantic . . . . . . . 

East North Central. . . . 

Eaat South Central . . . 

West North Central. . . 

West South Central. . . 

Mountain . . . . . . . . . . . 

Pacific . . . . . . . . . . . . . 

States included 

Connecticut, Maine, Maaaachusetts,


New Hampahire, Rhode Island, Ver­


mont


New Jersey, New York, Pennsyl­


vania


Delaware, District of Columbia,


Florida, Georgia, Maryland, North


Carolina, South Carolina, Virginia,


Weat .Virginia


Illinois, Indiana, Michigan, Ohio,


Wisconsin


Alabama, Kentucky, Mississippi,


Tennessee


lowa, Kansas, Minnesota, Missouri,


Nebraska, North Dakota, South


Dakota


Arkansas, Louisiana, Oklahoma,


Texas


Arizona, Colorado, Idaho, Montana,


Nevada, New Mexico, Utah,


Wyoming


Alaska, California, Hawaii, Oregon,


Washington


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