文摘
To evaluate the performance of combined cytology and microcrystal detection in joint fluid for diagnosing septic arthritis.MethodsRetrospective single-center study of joint fluid samples from patients with manifestations suggesting acute or chronic arthritis. The absolute leukocyte count (/mm3) was recorded; as well as the differential counts, particularly of neutrophils (%). Microcrystals were sought and bacteriological cultures performed. Septic arthritis was defined as positive cultures of joint fluid or blood samples. Diagnostic performance was assessed based on sensitivity, specificity, the receiver-operating characteristics (ROC) curve with the area under the curve (AUC), and the positive and negative likelihood ratios (LR+ and LR−).ResultsTwo hundred and eight joint fluid samples were included. The diagnoses were septic arthritis (n = 28), chondrocalcinosis (n = 41), gout (n = 28), rheumatoid arthritis (n = 33), spondyloarthritis (n = 31), osteoarthritis (n = 18), and undifferentiated arthritis (n = 29). Among cytological parameters, those having the best diagnostic performance were the neutrophil count (cutoff, > 50,000/mm3), the leukocyte count (cutoff, > 50,000/mm3), and the percentage of neutrophils (cutoff, > 95%); corresponding LR+ values were 8.93, 5.76, and 4.55, respectively. Neutrophil percentages lower than 80% had an LR− value of 0.07. Combining these cytological variables with the absence of crystals improved the diagnostic performance, yielding LR+ values of 11.36, 10.94, and 10.82 for neutrophils > 95%, neutrophils > 50,000/mm3, and leukocytes > 50,000/mm3, respectively.ConclusionCombining cytological characteristics of joint fluid with the absence of crystals benefits the diagnosis of septic arthritis.