Aims. This study aimed to assess the performance of an automated multiplex polymerase chain reaction (mPCR) technique for rapid diagnosis of native joint septic arthritis. Patients and Methods. Consecutive patients with suspected septic arthritis undergoing aseptic diagnostic joint aspiration were included. The aspirate was used for analysis by mPCR and conventional microbiological analysis. A joint was classed as septic according to modified Newman criteria. Based on receiver operating characteristic (ROC) analysis, the area under the ROC curve (AUC) values of the mPCR and the synovial fluid culture were compared using the z-test. A total of 72 out of 76 consecutive patients (33 women, 39 men; mean age 64 years (22 to 92)) with suspected septic arthritis were included in this study. Results. Of 72 patients, 42 (58%) were deemed to have septic joints. The sensitivity of mPCR and synovial fluid culture was 38% and 29%, respectively. No significant differences were found between the AUCs of both techniques (p = 0.138). A strong concordance of 89% (Cohen’s kappa: 0.65) was shown. The mPCR failed to detect Staphylococcus aureus (n = 1) and Streptococcus pneumoniae (n = 1; no primer included in the mPCR), whereas the synovial fluid culture missed six microorganisms (positive mPCR: S. aureus (n = 2), Cutibacterium acnes (n = 3), coagulase-negative staphylococci (n = 2)). Conclusion. The automated mPCR showed at least a similar performance to the synovial fluid culture (the current benchmark) in diagnosing septic arthritis, having the great advantage of a shorter turnaround time (within five hours). Cite this article: Bone Joint J 2019;101-B:288–296

Aims. Smoking is associated with post-operative complications but smokers often under-report the amount they smoke. Our objective was to determine whether a urine dipstick test could be used as a substitute for quantitative cotinine assays to determine smoking status in patients. Patients and Methods. Between September 2013 and July 2014 we conducted a prospective cohort study in which 127 consecutive patients undergoing a planned foot and ankle arthrodesis or osteotomy were included. Patients self-reported their smoking status and were classified as: ‘never smoked’ (61 patients), ‘ex-smoker’ (46 patients), or ‘current smoker’ (20 patients). Urine samples were analysed with cotinine assays and cotinine dipstick tests. Results. There was a high degree of concordance between dipstick and assay results (Kappa coefficient = 0.842, p < 0.001). Compared with the quantitative assay, the dipstick had a sensitivity of 88.9% and a specificity of 97.3%. Patients claiming to have stopped smoking just before surgery had the highest rate of disagreement between reported smoking status and urine testing. Conclusion. Urine cotinine dipstick testing is cheap, fast, reliable, and easy to use. It may be used in place of a quantitative assay as a screening tool for detecting patients who may be smoking. A positive test may be used as a trigger for further assessment and counselling. Cite this article: Bone Joint J 2016;98-B:1418–24