A Comparative Study of Serum and Synovial Fluid Levels of Uric Acid between Patients with Gout and Other Arthritides
Suparaporn Wangkaew MD*, Nuntana Kasitanon MD*, Sith Hongsongkiat MD*, Chaiyut Tanasombat BSc**, Waraporn Sukittawut BSc*, Worawit Louthrenoo MD*
Affiliation : * Division of Rheumatology, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand ** Division of Clinical Chemistry Laboratory, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
Background : The urate levels and the correlations of urate levels between the serum and synovial fluid (SF) of many arthritic
diseases have not been well described.
Objective : Compare urate levels in the serum and SF of gouty arthritis, calcium pyrophosphate dihydrate deposition disease
(CPPD), rheumatoid arthritis (RA), septic arthritis, ankylosing spondylitis (AS), and osteoarthritis (OA) patients.
Material and Method: Paired samples of serum and SF from 95 patients comprised of 33 patients with gout, 22 with CPPD,
18 with RA, nine with septic arthritis, three with AS, and 10 with OA were collected simultaneously for urate measurement
by photometric test.
Results : Ninety-five patients, including 53 males, with mean (SD) age of 64.1(15.3) years were recruited. In gout, serum
and SF urate levels were significantly higher than those of CPPD, RA, septic arthritis, AS, and OA (p<0.01). In all the study
population, the serum/SF ratios of urate levels of gout were not different across all groups. However, after excluding
24 patients with creatinine >1.5 mg/dl, the serum/SF ratios of urate were significantly lower in gout compared with the
others (p = 0.02). There were strongly positive correlations between serum and SF urate levels in gout similar to CPPD,
RA, septic arthritis, AS, and OA (r = 0.81-0.91, p<0.01).
Conclusion : Despite the highest level of serum and SF urate across all groups, the serum/SF urate ratio in gout patients
was the lowest, which suggests that SF urate levels are uniquely higher than their serum. In addition, the levels of serum
urate of the entire groups strongly reflect their SF levels.
Keywords : Synovial fluid, Urate, Uric acid
