Comparison of PCR, Wright Agglutination Test and Blood Culture for Diagnosis of Brucellosis in Suspected Patients

Abstract

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.

Epidemiological and Clinical Features of Brucellosis in the Country of Georgia

“…Some suggest the use of blood cultures and/or real-time PCR for confirmation of Wright-positive cases [23], whereas others suggest that if the agglutination test is negative, culture and/or ELISA, and/or real-time PCR should be performed [24]. In developing countries such as Georgia with limited laboratory capabilities for culture and automated culture systems, as well as PCR other tests such as ELISA, offer an alternative for diagnosis [25].…”

Laboratory Diagnosis of Human Brucellosis

“…Naturally, the Castañeda method is not specific for brucellae, and other microorganisms, including true pathogens and contaminants, may grow in the flask; therefore, full identification of the isolate is required. Although the performance of the Castañeda method has been superseded in recent years by automated blood culture systems, it is still extensively employed in countries of endemicity with limited economic and technical resources due to its low cost and practicality (27,(42)(43)(44)(45)(46)(47).…”

Predictive Contribution of Neutrophil/Lymphocyte Ratio in Diagnosis of Brucellosis

“…Most commonly serum agglutination test is used for diagnosis of brucellosis and its result conforms with complement fixation or Coombs' test [ 4 ]. In the diagnosis of brucellosis the gold standard test is culture of brucellosis [ 5 ]. Which patients must we suspect for brucellosis?…”