Longitudinal, expert, all data procedure for psychiatric diagnosis in patients with psychoactive substance use disorders.

The Longitudinal, Expert, All Data (LEAD) procedure has been proposed as a criterion for the assessment of the procedural validity of diagnostic instruments. The authors evaluated the procedure's test-retest reliability and whether it enhanced diagnosis based on a single interview. Data were collected using interviews and questionnaires to assess current and lifetime substance use disorders and common comorbid disorders in 100 patients recruited from a substance abuse treatment program. An initial diagnostic interview was conducted by a primary expert who, at the end of treatment, formulated LEAD diagnoses for each patient, based on the results of the research assessment and all available clinical records. Secondary experts used a similar procedure in a subsample of 40 patients to provide a measure of test-retest reliability. Overall reliability of LEAD diagnoses was good, though it varied from excellent for substance use disorders to poor for some comorbid psychiatric disorders. As a consequence of the LEAD procedure, the total number of substance use diagnoses increased significantly, with no effect on diagnostic reliability. Based on these findings, we conclude that, while the overall reliability of the LEAD procedure is comparable to other diagnostic methods, there was considerable variability among groups of diagnoses. The additional cost of the procedure would appear to be justified only when diagnostic sensitivity is at a premium and principally for the diagnosis of psychoactive substance use disorders. Before it is widely used as a diagnostic criterion measure, the utility of the LEAD procedure should be evaluated in a variety of patient samples and under varying circumstances.