Bacterial or crystal-associated arthritis? Discriminating ability of seruminflammatory markers

A retrospective study. of patients with culture-verified septic arthritis ( n=54) and polarizing microscopy verified crystal-associated arthritis (n=34 ) was conducted with the objective to identify discriminating laboratory pa rameters in serum. Serum CRP levels (p=0.002) and ESR (p=0.03) were signifi cantly higher on admission in patients with septic arthritis than in those with crystal-associated arthritis. The peripheral WBC counts did not differ between the two groups, nor did the lactoferrin or procalcitonin (PCT) lev els. Serum TNF alpha concentrations on admission were higher in patients wi th septic arthritis than in those with crystal-associated arthritis (p= 0.0 008). Significant differences were also found for IL-8 (p=0.01) and G-CSF ( p=0.002), but not for IL-6 (p=0.5). However, extensive overlap between the groups was present, resulting in low sensitivity, specificity and predictiv e value for each test. Determining serum levels of acute phase reactants, i ncluding cytokines, does not replace careful synovial fluid examination, in cluding direct microscopy and cultivation.