Statistics for a Diagnostic Model

In recent years, several methods have been proposed for making medical diagnoses by machine (Ledley and Lusted 1959, Crumb and Rupe 1959). A method devised by Brodman et al. 1959, 1960 has been used to program a high-speed electronic computer for making presumptive medical diagnoses using only information relating to the age, sex, and responses of patients to a standardized health questionnaire. The method assigns patients to none, one, or several of 60 selected disease categories. The 60 diseases most frequently diagnosed by hospital physicians in men and the 60 diseases in women were chosen for study. The method was developed with data referring to 5,929 consecutive adult white patients (2,718 men and 3,211 women) admitted to the outpatient departments of The New York Hospital, a large general hospital, during the 18-month period beginning July 1, 1948. It was tested with data referring to 2,745 consecutive adult white patients (1,280 men and 1,465 women) admitted during the 12-month period beginning January 1, 1956. Each patient's symptoms were elicited through a printed form, the Cornell Medical Index-Health Questionnaire (CMI). The CMI was devised to collect diagnostically important elements of the medical history given by general medical patients, without expenditure of a physician's time. Solely with these data, a physician can often correctly predict which diseases will be found in subsequent examination (Brodman et al. 1951). Additional data abstracted for analysis from the hospital records include each patient's sex and age, along with the diagnoses made by hospital physicians after eliciting a history and performing physical and laboratory examinations. These diagnoses for the 1948-1949 data were coded according to the U. S. Public Health Service Manual for Coding Causes of Illness 1944 and form the standard against which the method is evaluated.