[Laboratory diagnosis and antibacterial therapy in joint diseases]

The indication for arthrocentesis is a difficult medical decision. Once obtained, however, puncture fluid is unique and important examination material which should always be thoroughly analyzed for diagnostic purposes, and also stored in a serum bank. In addition to the total protein and/or albumin fractions, the individual immunoglobulins in particular have proved to be a key parameter: they enable mechanical, hydro, inflammatory, and chronic-inflammatory processes to be distinguished. Especially in combination with the serum value, CRP is the best marker for acute inflammatory and traumatic changes. Determination of complement factors C1, C4, and C3, also of total complement activity, CH50 and of rheumatism factors, enables chronic-immunologic/rheumatic conditions to be diagnosed and their course evaluated. Bacteriologic study of punctates should always be included--not least as confirmation for the examiner--as also should cytologic and histologic examination of the sediment. Since, with bacterial etiology, the infections concerned are usually in their later stages, e.g., gonorrhea, yersinia, rubella, arthritis, antibody assays should always be performed in the serum and the joint in addition to these tests. Controversy still surrounds the question of local binding of immunoglobulin antibody complement components in the synovia itself; the present authors' findings hitherto also fail to furnish any definitive data on this issue.