Korean J Intern Med.  2014 May;29(3):361-369. 10.3904/kjim.2014.29.3.361.

Clinical factors and treatment outcomes associated with failure in the detection of urate crystal in patients with acute gouty arthritis

• Park JW
• Ko DJ
• Yoo JJ
• Chang SH
• Cho HJ
• Kang EH
• Park JK
• Song YW
• Lee YJ

• KMID: 1792062
• DOI: http://doi.org/10.3904/kjim.2014.29.3.361

Abstract

BACKGROUND/AIMS
To investigate the rate of detection of monosodium urate (MSU) crystals in the synovial fluid (SF) of patients with acute gouty arthritis and factors associated with false-negative results.
METHODS
A total of 179 patients with acute gouty arthritis who had undergone SF crystal examination were identified from the data warehouse of two university hospitals. Clinical and laboratory data were obtained from the medical records.
RESULTS
The overall rate of detection of MSU crystals was 78.8%. In univariate analyses, the only significant differences between the variables of crystal-negative and crystal-positive patients were a lower C-reactive protein level (p = 0.040) and fewer patients undergoing emergent surgery in the crystal-positive group (p = 4.5 x 10(-6)). In logistic regression analyses, MSU crystal-negative results were significantly associated with the interval from arthritis onset to crystal examination (p = 0.042), and this was the most significant risk factor for arthroscopic surgery (p = 2.1 x 10(-4)). Seventeen patients who underwent arthroscopic surgery had a significantly longer hospital stay (p = 0.007) and a significant delay in gout treatment (p = 8.74 x 10(-5)). The distribution of crystal-negative patients differed significantly between the SF samples that were evaluated by both the laboratory medicine and the rheumatology departments (p = 1.2 x 10(-14)), and the kappa value was 0.108.
CONCLUSIONS
Although several clinical features were associated with detection failure, SF MSU crystal identification was critically dependent on the observer. Considering the impact on the treatment outcomes, implementation of a quality control program is essential.

Keyword

Gout; Uric acid; Synovial fluid; Microscopy, polarization

MeSH Terms

Acute Disease
Aged
Arthritis, Gouty/diagnosis/*metabolism/*surgery
Arthroscopy
Biological Markers/metabolism
Crystallization
False Negative Reactions
Female
Hospitals, University
Humans
Length of Stay
Logistic Models
Male
Microscopy, Polarization
Middle Aged
Observer Variation
Predictive Value of Tests
Reproducibility of Results
Republic of Korea
Retrospective Studies
Synovial Fluid/*metabolism
Time Factors
Time-to-Treatment
Treatment Outcome
Uric Acid/*metabolism
Biological Markers
Uric Acid