Quality and use of synovial fluid tests open to question

The use of synovial fluid tests gives cause for concern, despite their obvious diagnostic value in certain joint diseases, suggests a comprehensive literature review of their applications from the University of Bristol.

The review, based on 300 papers out of an initial trawl of 6556, published between 1980 and 2001, confirms that synovial fluid analysis can be of major diagnostic value. It is especially useful in acute arthritis, when a crystal arthropathy or septic arthritis is suspected, and in intercritical gout.

But standards fall well short of optimal for the traditional assays of microbiology, white blood cell counts, and microscopy for pathogenic crystals. And there are “worrying variations” in reported sensitivity, specificity, and reliability, and scant evidence of quality control, it finds.

Furthermore, the use of the newer cytological and biochemical marker assays is based primarily on anecdotal evidence, with no research into their sensitivity, specificity, and reliability, it says. Added to which, the well known difficulties of interpreting the results of biochemical assays restrict their use in clinical medicine.

The authors point out that the poor standards highlighted by the review may be partly due to the fact that synovial fluid analysis is routinely under researched, excluded from routine diagnostic pathology services, and is a victim of low throughput of samples in most units.

More research is urgently needed, say the authors, who conclude that the immediate priority should be to rationalise the use, and improve the quality control, of synovial fluid assays, given their importance in acute arthritis.