title: A method for counting monosodium urate crystals in synovial fluid.
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.
authors.affiliation: Research Laboratory and Academic Division of Clinical Rheumatology, Department of Internal Medicine, University of Genova. paola.montagna@unige.it.
authors.forename: P
authors.initials: P
authors.lastname: Montagna
authors.forename: R
authors.initials: R
authors.lastname: Brizzolara
authors.forename: C
authors.initials: C
authors.lastname: Ferrone
authors.forename: M
authors.initials: M
authors.lastname: Cutolo
authors.forename: S
authors.initials: S
authors.lastname: Paolino
authors.forename: M A
authors.initials: MA
authors.lastname: Cimmino
mesh_terms: D000975:Antioxidants / Q000032:analysis*; D015415:Biomarkers / Q000737:chemistry; D003460:Crystallization; D018450:Disease Progression; D005240:Feasibility Studies; D006073:Gout / Q000175:diagnosis / Q000378:metabolism*; D006801:Humans; D007958:Leukocyte Count / Q000379:methods; D008859:Microscopy, Polarization / Q000379:methods; D009504:Neutrophils; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013582:Synovial Fluid / Q000737:chemistry*; D014527:Uric Acid / Q000032:analysis*
chemical_list: D000975:Antioxidants; D015415:Biomarkers; D014527:Uric Acid