Culture examination is still considered the gold standard for diagnosis of bone and joint infections, including prosthetic ones, even if in up to 20–30% of cases, particularly prosthetic joint infections, it fails to yield microbial growth. To overcome this limitation, determination of markers of inflammation and or infection directly in joint fluid has been proposed.

Aim of this study was to evaluate the applicability of measurement of lecukocyte esterase (LE), C-reactive protein (CRP) and glucose in synovial fluid for diagnosis of bone and joint infections.

Synovial fluids from 80 patients were aseptically collected and sent to laboratory for microbiological cultures. After centrifugation at 3000 rpm for 10 minutes, pellet was used for cultures, while the surnatant was used for determination of LE, CRP and glucose. LE and glucose were evaluated by means of enzymatic colorimetric strips developed for urinanalysis. One drop of synovial fluid was placed on the LE and on the glucose pads and the results were read after about 120 seconds. A LE test graded + or ++, and a glucose test equal to trace or negative were considered suggestive for infection. CRP was measured by an automated turbidimetric method.

On the basis of clinical findings, microbiological, haematological and histological analyses patients were retrospectively divided into 2 groups. Group 1 comprised 19 infected patients (12 males, 7 females age: 70.6 ± 10.3 yrs, range: 47 – 88 yrs) while Group 2 included 61 aseptic patients (32 males and 29 females, age: 61.5 ± 16.3 yrs, range: 15 – 84). Sensitivity of the three tests was 89.5%. 84% and 73,7% for LE, CRP and glucose, respectively. Specificity was 98.4%, 88.5% and 70% for LE, CRP and glucose, respectively. Positive and negative predictive values were 94.4% and 96.8% for LE, 69.6% and 94.6% for CRP and 77.8% and 89.6% for glucose test. When LE was combined with CRP, sensitivity increased to 94.7%, while no differences were observed for LE combined with glucose.

Leukocyte esterase has proven to be a rapid, simple and inexpensive test to rule in or out bone and joint infections. Combination of its measurement with that of CRP increased sensitivity. In conclusion, the combination of leukocyte esterase and CRP may represent a simple and useful tool for diagnosis of bone and joint infections.