Which tests are most reliable in differentiating septic arthritis, crystal arthritis, and inflammatory arthritis in patients with acute hot joints?
In this meta-analysis, individual tests are not accurate enough to rule in or rule out septic arthritis. On the other hand, microscopic analysis of joint fluid was useful in identifying patients with crystal arthritis. The authors identified significant challenges in using tests to identify patients with inflammatory arthritis.
Plan de l'etude:
These authors searched several databases and registries to identify English-language studies that evaluated patients of any age with hot swollen native joints with onset less than 6 weeks before enrollment. They included 49 studies with sample sizes ranging from 6 to 1161 patients. The studies had to use one or more serum or synovial fluid markers compared with a reference standard of clinical assessment plus joint fluid microscopy and culture. Overall, the studies were of mixed quality; some were at low risk of bias for all domains, while others were ... not.
To identify patients with septic arthritis, the authors found studies that evaluated several serum tests (procalcitonin, erythrocyte sedimentation rate [ESR], C-reactive protein [CRP], white blood cell [WBC] count, uric acid, TIMP-1, CTX-II, and calprotectin). Of those tests, procalcitonin (using 10 µg/L), TIMP-1, and CTX-II were very specific (values from 0.89 - 1.0), but not very sensitive (0.087 - 0.727). Conversely, ESR and CRP are quite sensitive, but not very specific. Synovial fluid tests (glucose, lactate, leucocyte esterase, polymorphonuclear leucocytes, procalcitonin, tumor necrosis factor-alpha, and WBC count) varied widely (sensitivity ranged from 0.36 - 0.94 and specificity from 0.65 - 0.99). The leucocyte esterase assay was most sensitive (++ or +++; 0.94) and lactate was most specific (10 mmol/L or higher; 0.99).
The authors identified only 2 studies, each using synovial fluid tests, for distinguishing crystal from non-crystal arthritis. Crystal analyses (monosodium urate and calcium pyrophosphate) were sensitive (0.89 and 0.93, respectively) and specific (1.0 and 0.88, respectively). Finally, because of variable definitions of inflammatory arthritis and the heterogeneity of study designs and thresholds, the authors did not report data on tests for identifying patients with inflammatory arthritis.
Henry C. Barry, MD, MS
Michigan State University
East Lansing, MI