Use of the clinical laboratory in the diagnosis and treatment of depression

This article reviews the importance of laboratory testing in the diagnosis of depressive disorders and for management during treatment. There is no useful test to establish the presence of a Major Depressive Episode, but medical conditions requiring laboratory testing should be excluded before arriving at a diagnosis. Treatment may lead to physiologic dysfunction warranting monitoring various laboratory functions. The following tests should be considered in establishing diagnosis and to establish baseline levels for comparison in subsequent monitoring: ■ Electrolytes ■ TSH (and free T4 if TSH is abnormal) ■ CBC with platelet count ■ Creatinine and BUN ■ LFTs (AST, alkaline phosphatase) ■ Calcium and phosphate ■ Pregnancy testing (hCG) for selected female patients. Lithium, carbamazepine, and valproic acid levels should be monitored when these medications are used to treat patients with depression.