Synovial fluid lactic acid in septic arthritis

Area of Science:

• Rheumatology
• Biochemistry
• Infectious Diseases

Background:

• Inflammatory arthritis encompasses various conditions, including rheumatoid arthritis, reactive arthritis, and gout.
• Distinguishing septic arthritis from non-septic inflammatory arthritis is crucial for timely and appropriate treatment.
• Synovial fluid analysis plays a key role in diagnosing joint infections.

Purpose of the Study:

• To evaluate the utility of synovial fluid lactic acid concentration in differentiating septic arthritis from non-septic arthritides.
• To determine the diagnostic threshold for lactic acid in septic arthritis.

Main Methods:

• Enzyme-based assay was used to measure lactic acid concentrations in synovial fluid.
• Samples were collected from 71 patients with inflammatory arthritis, including septic and non-septic cases.
• Lactic acid levels were correlated with the diagnosis of septic arthritis.

Main Results:

• Patients with septic arthritis consistently showed lactic acid concentrations ≥ 11 mmol/l (12 patients).
• Patients with non-septic arthritis (rheumatoid arthritis, reactive arthritis, gout) had lactic acid concentrations ≤ 10.2 mmol/l (54 patients).
• Two patients with gonococcal arthritis did not exhibit elevated lactic acid levels.

Conclusions:

• Synovial fluid lactic acid measurement is an accurate and reproducible method for differentiating septic from non-septic arthritis.
• This enzyme method can guide treatment decisions before definitive microbiological confirmation.
• Interpretation requires caution in patients with recent antibiotic use or suspected gonococcal arthritis.