SOURCES OF DIAGNOSTIC UNCERTAINTY FOR CHRONICALLY PSYCHOTIC COCAINE ABUSERS

Objective: This study determined the sources and frequency of diagnost ic uncertainty for patients with chronic psychosis and active cocaine abuse or dependence and assessed the usefulness of prospective follow- up in clarifying diagnosis. Methods: A total of 165 male patients with chronic psychoses and cocaine abuse or dependence on inpatient units of a Veterans Affairs medical center were evaluated using the Structur ed Clinical Interview for DSM-III-R (SCID-R), urine tests, hospital re cords, and interviews with collateral sources. An algorithm allowing k ey SCID-R items and diagnostic criteria to be designated as provisiona lly met or uncertain was applied, resulting in a provisional diagnosis and a list of alternate diagnoses. The assessment was repeated 18 mon ths later in an attempt to resolve diagnostic uncertainty. Results: In 30 cases (18 percent), initial assessment produced a definitive diagn osis, including 21 cases of schizophrenia, six of schizoaffective diso rder, and three of psychostimulant-induced psychotic disorder In the o ther 135 cases, a definitive diagnosis could not be reached because of one or more soul ces of diagnostic uncertainty, including insufficien t periods of abstinence (78 percent), poor memory (24 percent), and in consistent reporting (20 percent). Reassessment at 18 months led to de finitive diagnoses in 12 additional cases. Conclusions: It was frequen tly difficult to distinguish schizophrenia from chronic substance-indu ced psychoses. Rather than concluding prematurely that psychotic sympt oms are, or are not, substance induced, clinicians should initiate tre atment of both psychosis and the substance use disorder in uncertain c ases. The persistence or resolution of psychosis during abstinence and additional history from the stabilized patient or collateral sources map clarify the diagnosis.