Abstract
Since 1949 the diagnoses given to all patients admitted to psychiatric hospitals in England and Wales have been collected and tabulated, initially by the General Register Office and more recently by the Ministry of Health and its successor the Department of Health and Social Security. These data are published regularly and have been used for many purposes—to follow trends in admission and discharge rates, to predict future bed and manpower needs, and in international comparisons. Before 1970 there was no official nomenclature and psychiatrists used whatever diagnostic terms they wished when completing the S.B.H.15 index cards provided for each patient (Department of Health and Social Security, 1970, Appendix A). In the Department of Health these diagnoses were converted into 3-digit numbers, using a complex code developed by the General Register Office (D.H.S.S., 1970, Appendix B), and finally these code numbers were grouped together to make them conform as well as possible with the nomenclature of the 7th edition of the International Classification of Disease (ICD 7). Inevitably this procedure was unsatisfactory. It was cumbersome; it only permitted a few broad diagnostic categories to be distinguished with any confidence; and it involved making a number of arbitrary assumptions about the relationship between the different nomenclatures involved.