A method for counting monosodium urate crystals in synovial fluid

  • P. Montagna Research Laboratory and Academic Division of Clinical Rheumatology, Department of Internal Medicine, University of Genova, Italy.
  • R. Brizzolara Research Laboratory and Academic Division of Clinical Rheumatology, Department of Internal Medicine, University of Genova, Italy.
  • C. Ferrone Research Laboratory and Academic Division of Clinical Rheumatology, Department of Internal Medicine, University of Genova, Italy.
  • M. Cutolo Research Laboratory and Academic Division of Clinical Rheumatology, Department of Internal Medicine, University of Genova, Italy.
  • S. Paolino Research Laboratory and Academic Division of Clinical Rheumatology, Department of Internal Medicine, University of Genova, Italy.
  • M.A. Cimmino | cimmino@unige.it Research Laboratory and Academic Division of Clinical Rheumatology, Department of Internal Medicine, University of Genova, Italy.

Abstract

This study was aimed to standardize the technique for counting monosodium urate (MSU) crystals in the synovial fluid (SF) of patients with gout. A total of 52 SF specimens were examined under a polarized light microscope. The amount of SF ranged between 0.1 and 45 mL (median 3 mL). MSU crystals were counted in four areas with the same size at 400x magnification. Cytological examination of the same specimens was also performed. Median leukocyte count was 400 cells/mm3 (range 50-14,000 cells/mm3), with a median percentage of polymorphonuclear leukocytes of 9% (range 0%-98%). Median crystal count was 179.5 (range 3-1600). Inter- reader and intra-reader agreement in crystal counting were good with a weighed k of 0.89 [95% confidence interval (CI) 0.85-0.94] and 0.89 (95% CI 0.84-0.93), respectively. Our data indicate that the SF MSU crystal count is a feasible and highly reliable technique.

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Published
2015-06-30
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An eye in the lab
Keywords:
Gout, Monosodium urate crystals, Synovial fluid, Polarized microscopy.
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How to Cite
Montagna, P., Brizzolara, R., Ferrone, C., Cutolo, M., Paolino, S., & Cimmino, M. (2015). A method for counting monosodium urate crystals in synovial fluid. Reumatismo, 67(1), 29-32. https://doi.org/10.4081/reumatismo.2015.827