Comparison of a Novel Test (ODAK Brucella Coombs Gel Test) with Commonly Used Serological Tests in Human Brucellosis.

Background: Since Brucellosis is difficult to diagnose based on clinical symptoms, the diagnosis mostly relies on the results of serological testing. ODAK Brucella Coombs Gel Test is a novel and rapid gel microcolumn agglutination test which is performed in microcolumns containing gel matrix and Coombs antibodies. In this study, we aimed to compare ODAK Brucella Coombs Gel Test with other commonly used serological tests.

Methods: 150 blood samples of patients, preliminarily diagnosed as Brucellosis, were included in this study. Rose Bengal (RB), ODAK Brucella Coombs Gel Test (CGT), Brucellacapt (BCAP), and Standard Agglutination Test (SAT) were performed for all samples. Also, Coombs Agglutination Test (CAT) was performed for all SAT negative samples. 1/160 and above titers were accepted as positive result except RB which is a qualitative test.

Results: 100 (67%) out of 150 samples were found positive by RB. All of the 50 RB negative samples were also found negative by SAT and CAT test. However, 2 (4%) and 7 (14%) of them were positive by CGT and BCAP tests, respectively. Additionally, among 100 RB positive samples, only 68, 77, and 87 were positive by SAT+CAT combination, CGT, and BCAP tests, respectively.

Conclusions: Currently, CGT is the only rapid (< 1 hour) serological test in which Coombs antibodies are used. Our results showed that negative results of RB, as a screening test, are not reliable enough as compared to CGT. However, positive RBT results confirmed with SAT were almost always, in most of the cases with higher titers, positive with CGT and BCAP. On the other hand, even if SAT is found negative with RB positivity, samples still must be investigated with CAT, CGT or BCAP. Consequently, CGT may be used as a rapid screening test instead of RB and it furthermore has similar sensitivity with the other confirmation tests in which Coombs antibodies are used. Therefore, ODAK Brucella Coombs Gel Test seems to be a very useful diagnostic tool for Brucellosis.