Present status of laboratory diagnosis of sarcoidosis.

The clinical pathologist is involved in the diagnosis of sarcoidosis in a variety of ways. Many of the traditional hemotologic and biochemical studies performed in study of patients suspected of having sarcoidosis are, however, of little diagnostic assistance. Hypercalcemia is now an infrequent manifesta­ tion of sarcoidosis and routine study of calcium metabolism in asymptomatic patients with early sarcoidosis is rarely rewarding. Serum globulin fractions are increased particularly in black patients with sarcoidosis but the changes are non-specific and like serum immunoglobulin level measurements are like­ wise of little diagnostic help. The Kveim test has not found wide use because of the lack of standardized and stable testing materials. Biopsy methods remain the best method of demonstrating the typical epithelioid granulomas char­ acteristic of sarcoidosis. Mediastinoscopy and lung biopsy have the highest yield and should be utilized when readily accessible lesions such as skin, palpable lymph nodes and subcutaneous nodules are not available. The de­ velopment of in vitro techniques for measurement of delayed hypersensitivity should permit an in vitro diagnostic test for sarcoidosis if a specific antigen can be obtained from splenic or lymph node suspensions. An important responsi­ bility of the laboratory is the detection of mycobacterial or fungal diseases which may simulate or superinfect sarcoidosis. Mycobacterial infection has been encountered rarely in recent years, but aspergillosis and cryptococcus have proven to be common problems in patients with sarcoidosis. Serologic tests should be widely available for the prompt diagnosis of these important infections. Sarcoidosis is a multi-system disorder of as yet unknown cause, commonly involving mediastinal and peripheral lymph nodes, lungs, liver, eyes and skin, with less fre­ quent involvement of many other organs and tissues. The characteristic histopatho­ logic feature is multiple epithelioid cell granulomas without caseation. The epi­ thelioid cell granulomas may resolve com­ pletely or proceed to fibrosis. Depression of delayed-type hypersensitivity and a Kveim reaction are often demonstrable. Local sar­ coid reactions, limited to a single organ as well as granulomas due to demonstrable