Development and Validity of a Computerized Method for Diagnoses of Functional Psychoses (Diax)

Comparison of the results of studies within psychiatry are often complicated by the uncertainty of whether the different authors use the same diagnostic critaria for the probands in the studies. In the “International Pilot Study of Schizophrenia” (IPSS) (WHO), patients with functional psychoses from the nine participating centres were examined with standardized instruments. This study is based on data collected during the initial examination and a 2‐year follow‐up of patients included in the IPSS. The aim was to develop and test a method based on symptoms which diagnosed the patients in a standardized way. A computer programme using 39 symptom groups was developed, (DIAX). (A manual is included in the Appendix). In order to evaluate the diagnoses arrived at by DIAX, comparison was made with clinical diagnoses at initial examination and at follow‐up. For the total of 1202 patients from nine countries, the overall agreement was 73%. The comparison also showed interesting similarities and differences among the centres. The validity of the method was supported by the following three analyses. The stability (diagnoses based on initial examination and follow‐up examination) was high. “Severe” disagreement was only about 10%. The prognosis of the two major diagnostic groups showed a significant difference. An examination of mental illness in the families showed that DIAX diagnoses could separate the two nuclear groups, those with mainly schizophrenia in the family and those with mainly affective psychoses in the family. Other results emerging from the study and the advantages and limitations of the method are discussed.