Rapid diagnosis of septic arthritis by quantitative analysis of joint fluid lactic acid with a monotest lactate kit.

The Monotest Lactate Kit (MLT) was compared with gas-liquid chromatography (GLC) for the rapid detection of septic arthritis. A total of 36 joint fluids were tested. Specimens were obtained from patients with septic arthritis (17 cases), inflammatory arthritis (18 cases), and degenerative arthritis (1 case). Specimens from 15 patients with bacterial arthritis had lactate levels above 65 mg/dl (mean, 318 mg/dl with the GLC method and 378 mg/dl with the MLT method). Three specimens from patients with gonococcal arthritis had levels that were not above 30 mg/dl (mean, 21 mg/dl with either the GLC or the MLT methods). Patients with inflammatory or degenerative disease yielded levels lower than 65 mg/dl (mean, 48 mg/dl with the GLC method and 46 mg/dl with the MLT method). Both methods proved to be equallly reliable in detecting septic arthritis, except for the gonococcal cases. Both methods are fast and easily adaptable to clinical laboratories; however, MLT was more definitive when quantitation was needed, required less fluid per speciment, and could be readily done at the bedside.