Septic arthritis (SA) is considered a medical emergency. The most common etiological agents are glucose consuming bacteria, so we evaluated the clinical utility of synovial fluid (SF) glucose levels and other biochemical parameters for supporting the diagnosis of the disease and their association with a positive bacteria culture and joint destruction.
Adult patients with SA diagnose were enrolled prospectively between July 2018 and October 2019. As control group, adults with knee osteoarthritis, meniscus and/or knee ligaments lesions were enrolled. SF samples were obtained from the joints by arthrocentesis/arthrotomy. Microbiological analyses of SF were performed using Brucella broth blood culture flasks, samples were incubated at 37°C with 5% CO2 for 24 hours. Gram stain, chocolate and blood agar were used for the identification and growth of the bacteria. SF glucose levels, pH and leukocyte esterase were measured as biochemical parameters using a glucometer and colorimetric test strips. The Outerbridge classification was used for grading the osteochondral injury. Furthermore, blood samples were collected from patients and control subjects for determining glucose levels.
We included 8 subjects with knee ligaments lesions, 6 with meniscus lesions and 5 with osteoarthritis as control group, as well as 20 patients with SA diagnose. The mean age of the patients was 57.8 years with a 65% of male predominance. The most common affected joint was the knee (85%). SF culture was positive in 60% of the cases and the most common etiological agent was Staphylococcus aureus (58.3%). SF glucose levels from patients were lower than the controls (P=0.0018) and showed the lowest concentration in patients with a positive culture (P=0.0004). There was also a difference between blood and SF glucose concentration from the positive culture patients (P<0.0001). Leucocyte esterase presented the highest values in positive culture patients (P=<0.0001) and a more acidic pH was found compared to the control group (P<0.0001). Regarding the osteochondral injury, the lowest concentrations of SF glucose were found in patients with a higher grade in the classification (P = 0.0046).
SF glucose and leukocyte esterase concentrations might be a quick and cheap useful parameter for the physician for distinguishing between bacterial infection and not infected joint. In addition, the lowest SF glucose levels might give information about the joint damage due to the disease.