Clinical factors and treatment outcomes associated with failure in the detection of urate crystal in patients with acute gouty arthritis.
OBJECTIVE
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 × 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 × 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 × 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 × 10(-14)), and the κ 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.
Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.
Jun Won
JW
Park
Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.
Dong Jin
DJ
Ko
Department of Internal Medicine, Armed Forces Capital Hospital, Seongnam, Korea.
Jong Jin
JJ
Yoo
Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
Sung Hae
SH
Chang
Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
Hyon Joung
HJ
Cho
Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
Eun Ha
EH
Kang
Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea. ; WCU Department of Molecular Medicine and Biopharmaceutical Sciences, Medical Research Institute, Seoul National University College of Medicine, Seoul, Korea.
Jin Kyun
JK
Park
Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea. ; WCU Department of Molecular Medicine and Biopharmaceutical Sciences, Medical Research Institute, Seoul National University College of Medicine, Seoul, Korea. ; Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
Yeong Wook
YW
Song
Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea. ; Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
Yun Jong
YJ
Lee
D000208:Acute Disease; D000368:Aged; D015210:Arthritis, Gouty / Q000175:diagnosis / Q000378:metabolism* / Q000601:surgery*; D001182:Arthroscopy; D015415:Biomarkers / Q000378:metabolism; D003460:Crystallization; D005188:False Negative Reactions; D005260:Female; D006785:Hospitals, University; D006801:Humans; D007902:Length of Stay; D016015:Logistic Models; D008297:Male; D008859:Microscopy, Polarization; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D056910:Republic of Korea; D012189:Retrospective Studies; D013582:Synovial Fluid / Q000378:metabolism*; D013997:Time Factors; D061665:Time-to-Treatment; D016896:Treatment Outcome; D014527:Uric Acid / Q000378:metabolism*
D015415:Biomarkers; D014527:Uric Acid
Gout; Microscopy, polarization; Synovial fluid; Uric acid