Repeat Examination of Synovial Fluid for Crystals: Is It Useful?

Abstract

Several studies have shown the lack of sensitivity of microscopic examination of synovial fluid for MSU or CPPD crystals [sensitivity, 78% (1) and 79% (2) for MSU and 12% (1) and 67%(2) for CPPD]. Not surprisingly, this leads to a lack of reproducibility of synovial fluid analyses (1)(2). The suboptimal sensitivity, frequently attributed to the low concentrations or the small sizes of the crystals, has been difficult to improve without resorting to clinically impractical methods such as crystal extraction from synovial fluid (3) or electron microscopy(4). Problems with sensitivity have led experts to caution that a negative examination by polarized light microscopy does not exclude the presence of small numbers of crystals (5).