The work of Ropes and Bauer (1953) has focused attention on the analysis of synovial fluid in the differential diagnosis of joint effusion. White blood cell total and differential counts, glucose assay, and mucin precipitation tests have thus all been applied to the distinction of non-inflammatory, mild inflammatory, severe inflammatory, and infectious effusions. These analyses do not, however, indicate the true origin of the effusion, and we have carried out this investigation to find out whether differential assay of lactate dehydrogenase (LDH) isoenzymes could yield more specific information.It is known that the percentage of polymorphonuclear cells (PMN) and of lymphocytes is different in non-inflammatory, inflammatory, and infectious effusions. Recent studies (Dioguardi, Agostoni, Fiorelli, and Lomanto, 1963;Bottomley, Locke, and Ingram, 1966;Hule, 1967) indicate that polymorphonuclear cells and lymphocytes have different LDH isoenzyme patterns. One may thus expect to find LDH shifts in parallel with the type of the cellular material. It could also be of interest to look for any enzyme contribution originating in the lining walls of the synovia.Vesell, Osterland, Bearn, and Kunkel (1962) and especially Cohen (1964), who studied the LDH activity of synovial fluid in rheumatic disease states, reported that total synovial fluid LDH was raised in patients with inflammatory articular disease, and found marked rises of LDH5 in total synovial fluids of rheumatoid, gouty, and infected joints. They only found a minimal increase of LDH5 in fluids from cases of degenerative joint disease. Although these observations suggest that this type of analysis will be of little diagnostic value, one must remember that Vesell and others (1962) studied only a limited number of cases, including several of ill-defined aetiology. Cohen (1964) used LDH isoenzyme differentiation only as a complement to other enzyme studies; he confined himself to a visual interpretation of the LDH patterns in a relatively small number of cases.We therefore felt that interesting results might be obtained by applying a quantitative technique of LDH differentiation to a large number of cases of well-established aetiology.We have also determined LDH isoenzyme patterns separately on cell-free fluid and on cellular material after ultrasonic disintegration.
MethodsSynovial fluids were aspirated with sterile precautions from different joints (knee, elbow, hip, ankle) without using local anesthetics. In supplement to the analyses mentioned, the fluids were also submitted to bacteriological culture and to differential count of the white blood cells.Before the determination of total LDH activity and analysis of the LDH patterns, a constant amount of the synovial fluid (10 ml.) was centrifuged at 50,000 G. and 100 C. temperature for 30 min. In this way a clear cell-free supernatant and a cellular sediment were obtained. The supernatant was used as such. The sediment was washed three times with saline and finally resuspended in exactly 5 ml. saline. This suspensio...