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

Two alternative methods for detecting vitamin B12 deficiency in a psychiatric population have been compared: the `direct' approach by microbiological assay of serum vitamin B12 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 B12 assayed. The indirect approach was found to be cheaper.