Bajada S, et al. - The medical notes, hematological and microbiology results of 310 patients who underwent revision for a painful TKA were assessed by the researchers in order to examine the role of plasma viscosity (PV) in the diagnosis of prosthetic joint infection (PJI) after painful total knee arthroplasty (TKA). Serum examinations including erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and PV were investigated. Between PV and both ESR and CRP, a strong relationship was found. For PV and for ESR, the area under the curve was 0.814 and 0.812, respectively. In diagnosing PJI, statistical analysis exhibited the non-inferiority of PV in comparison with ESR. A PV value of >= 1.81 mPa.s. had the best effectiveness of 82.1%. Merging a CRP >= 13.5 mg/l with a PV >= 1.81 mPa.s. in a serial test approach gave the maximum specificity of 97.9% and a positive probability ratio of 22.8. The sensitivity was 47.9% and a negative probability ratio of 0.53. Hence, in diagnosing PJI, PV was non-inferior to ESR. Its use was confirmed for clinical practice. It was concluded as cheaper, quicker, more effective and not affected by hematocrit levels or medication. Moreover, in combination with CRP >= 13.5 mg/l, a PV value >= 1.81 mPa.s. would be an sufficient cut-off to diagnose PJI.