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Quality control of synovial fluid crystal identification
  1. Robert von Essena,
  2. Aira M H Hölttäa,
  3. Raija Pikkarainenb
  1. aRheumatism Foundation Hospital, Heinola, Finland, bLabquality, Helsinki, Finland
  1. Dr R Pikkarainen, Labquality, Ratamestarinkatu 11, FIN-00520 Helsinki, Finland.


OBJECTIVE To establish a quality assessment programme for the diagnosis of crystal arthropathies by synovial fluid (SF) microscopy.

METHODS Three or four cytocentrifuge slides prepared from suitable patient SF specimens were distributed to 25–47 predominantly Finnish clinical laboratories once a year. Sodium urate crystals were included in every survey.

RESULTS Returns for the years 1989–1996 were reviewed. Laboratories that participated in > four surveys made on an average one error a year (range 0.25–2). The error rate for specimens containing abundant crystals was acceptable but it increased considerably for specimens showing few crystals per microscope field. No laboratory characteristic predictive of successful performance was found.

CONCLUSION Errors in quality assessment results for crystal identification were much more frequent than in the fields of, for example, clinical chemistry or microbiology. Despite efforts to provide educational feedback, no improvement was seen during the study period. Because of the dearth of data from other parts of the world it is not known for certain whether this study has merely pinpointed a local problem or if the same trend applies elsewhere.

  • synovial fluid
  • joint fluid
  • quality control
  • crystals

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