Comparison of PCR, Wright agglutination test and blood culture for diagnosis of brucellosis in suspected patients.

Brucellosis has long been prevalent in Iran, with considerable medical and economic importance. Timely diagnosis is needed for early management and effective prevention of its consequences in human beings and animals. Current diagnostic methods impose peculiar challenges in terms of analytical method performance. This study compares diagnostic sensitivity, specificity, predictive Value of Positive (PVP) and Predictive Value of Negative (PVN) for Polymerase Chain Reaction (PCR), Wright agglutination test and blood culture used for patients suspected of brucellosis. In 120 patients clinically suspected of brucellosis and referred by physicians to the Yazd central Medical Laboratory, some relevant demographic, occupational, nutritional and clinical data were collected. Also, venous blood samples were drawn for diagnosis of brucellosis using PCR, Wright agglutination test and blood culture techniques. The most frequent symptom of patients was arthralgia (82 cases, 68.3%). PCR was positive in 25 cases (20.8%), wright test in 21 patients (17.5%) and blood culture in 6 cases (5%). In 20 out of 21 wright-positive cases, PCR was positive and all of the culture-positive patients had positive PCR. Sensitivity, specificity, PVP and PVN of blood culture compared to PCR (as the gold standard test) were 24, 100, 100 and 86%, respectively, but the above parameters when PCR is compared with blood culture (as gold standard) were 100, 83, 24 and 95%, respectively. PCR has better analytical performances than blood culture for diagnosis of brucellosis and is suitable for confirmation of Wright-positive cases.