title: Synovial Fluid Findings and Demographic Analysis of Patients With Coexistent Intra-articular Monosodium Urate and Calcium Pyrophosphate Crystals.
abstract: OBJECTIVE
  The aim of this study was to investigate the characteristics of arthritis in which monosodium urate (urate) and calcium pyrophosphate (CPP) crystals coexisted in synovial fluid (SF) to aid patient management and set a baseline from which to investigate the pathophysiological basis of an unusual coexistence of 2 disorders.
  
  
  METHODS
  Synovial fluid analyses of 33,000 patients were reviewed, identifying those containing urate and/or CPP crystals. Synovial fluid cell count and differential cell count, together with patient age and gender, were retrieved from a computerized database spanning 22 years of SF analysis.
  
  
  RESULTS
  In 6983 consecutive SF samples containing crystals, CPP crystals were found in 3685 (53%), urate in 3127 (44.5%), and both in 171 (2.5%). These 171 cases were deemed to have a mixed crystal arthropathy (MCA). Patients with MCA were 77% male and 23% female, and the highest incidence was found in those aged 76 to 80 years.Most commonly (69.4% of cases of MCA), high numbers (>20/10 high-power field) of both crystals and an acute inflammatory cell count were found. In the remainder, other patterns of crystals and cells were observed, perhaps suggesting different clinical situations in which these crystals coexist.
  
  
  CONCLUSIONS
  This study presents evidence showing that with careful microscopic analysis the coexistence of urate and CPP crystals in a single joint is found in 2.5% of cases of crystal arthritis. The different patterns of SF findings and patient demography described here are novel and might have implications for patient management.
authors.affiliation: From Manchester Medical School, Manchester, England.
authors.forename: Emilia L
authors.initials: EL
authors.lastname: Heselden
authors.forename: Antony J
authors.initials: AJ
authors.lastname: Freemont
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001168:Arthritis / Q000175:diagnosis / Q000378:metabolism*; D002131:Calcium Pyrophosphate / Q000378:metabolism*; D003460:Crystallization; D003710:Demography; D005260:Female; D006801:Humans; D007958:Leukocyte Count; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013582:Synovial Fluid / Q000378:metabolism*; D014527:Uric Acid / Q000378:metabolism*
chemical_list: D014527:Uric Acid; D002131:Calcium Pyrophosphate