Economic and laboratory considerations in screening for vitamin B12 deficiency in psychiatric practice.

Two alternative methods for detecting vitamin B(12) deficiency in a psychiatric population have been compared: the ;direct' approach by microbiological assay of serum vitamin B(12) levels in all patients, and the ;indirect' approach where all patients are first screened for antigastric parietal cell antibodies and thereafter all positive reactors and other ;high-risk' patients have serum vitamin B(12) assayed. The indirect approach was found to be cheaper.