Is Wright Test an Appropriate Screening Test for Diagnosis of Brucellosis?

Abstract

Problem statement: Diagnosis of brucellosis is generally based on culture, polymerase chain reaction and serology. The first two methods are not accessible in all parts of world and are expensive. The routine method for diagnosis of brucellosis is considering Wright test as the first screening test; if the results are Wright positive’ Wright would be the next choice otherwise 2ME would be requested. This method of laboratory data collection is not appropriate and it is probable to have some cases of brucellosis missed and in clinical practice we observed that some cases of brucellosis are Wright negative but Coombs’ Wright positive. Approach: In this study we calculated sensitivity, specificity, positive predictive value, negative predictive value and likelihood ratio of Wright and Coombs’ Wright in brucellosis suspected patients. Results: 122 patients suspected to brucellosis were studied. 53.3% were female. Sensitivity and specificity Positive Predictive Values (PPV) and Negative Predictive Values (NPV) of Wright were 32.5% (CI_95%: 22.8-42.3), 96.4% (CI_95%: 89.5-100), 96.6% (CI_95%: 0.9-100) and 93.1% (CI_95%:83.8-100) respectively. Sensitivity, specificity, positive predictive value and negative predictive value for Coombs’ Wright were 97.7% (CI_95%: 94.6-100), 100% (CI_95%: 100-100), 100% (CI_95%: 100-100) and 93.1% (CI_95%:83.8-100) respectively. Conclusion: Coombs’ Wright is more sensitive than Wright for diagnosis of brucellosis. Instead of considering Wright, Coombs’ Wright and 2ME (mercaptoethanol) tests and interpretation of these three test we can just apply Coombs’ Wright and 2ME to reduce the expenditures and use a more sensitive test for diagnosis of brucellosis.