Comparison of a New and Rapid Method, Brucella Coombs Gel Test With the Other Methods in the Serological Diagnosis of Brucellosis

Abstract

Diagnosis of brucellosis basically depends on blood and/or bone marrow culture and demonstration of high titer specific antibody or seroconversion in serum. In routine serological diagnosis of the disease, after screening with Rose Bengal test, the positive samples are studied with standart tube agglutination (STA) test with serial dilutions. However false negative results can be seen in STA test due to the existence of blocking antibodies, this test should be verified with Coombs anti-Brucella (CAB) or immunocapture agglutination (ICA) tests. In recent years Brucella Coombs gel test (ODAK Brucella Coombs Gel Test, Toprak Medikal, Turkey) developed in our country, was available as a new and rapid agglutination based method. The test is performed in vials that contain Coombs antibodies within gel matrix and results are evaluated visually within two hours.The aim of this study was to compare the efficacy of Brucella Coombs gel test (BCGT) with STA, CAB and ICA methods in serological diagnosis of brucellosis. A total of 100 serum samples with suspected brucellosis sent to our laboratory between January 2012-August 2013 in which 31 high positive (≥ 1/160), 23 low positive (≤ 1/80) and 46 negative samples diagnosed with CAB test (Seromed, Turkey) were included in the study. All the samples were studied using titrations with STA (Seromed, Turkey), ICA (Vircell, Spain) and BCGT (Islab, Turkey) methods. With STA, CAB and BCGT tests ≥ 1/160, with ICA test ≥ 1/320 were accepted as positive titers. The correlation between the tests were evaluated with Cohen's kappa (κ) analysis. In our study, seven of the samples yielded positive results with STA, 30 with ICA, and 32 with BCGT. The number of the sera which yielded positive results with all three methods was 28. Two samples positive with CAB and BCGT resulted low titer/negative with ICA, one sample positive with ICA and BCGT resulted low titer/negative with CAB, and one low titer/negative sample with CAB and BCGT yielded positive with ICA test. STA test was not included in the statistical evaluation due to its very low positivity rate. According to the kappa analysis, almost perfect agreement was detected between the other methods (κ= 0.887 for CAB and ICA, κ= 0.977 for CAB and BCGT, κ= 0.907 for ICA and BCGT). In conclusion, BCGT method showed excellent correlation with both CAB and ICA tests; the application of the test was practical; resulted in a short time such as two hours and visually evaluation was determined to be practical compared to other methods. Although BCGT can be recommended for routine diagnostics, evaluation of specificity and sensitivity with comprehensive studies including a greater number of cases and control samples should be considered.

Comparison of a New and Rapid Method: Brucella Coombs Gel Test With Other Diagnostic Tests

“…İrvem et al. reported that BCGT was an easy and rapid method for Brucella diagnosis, and found that test results of BICA and BCGT in their study were perfectly consistent . Sensitivity, specificity, negative predictive, and positive predictive values of BCGT were reported to be relatively high compared to other tests .…”

“…ELISA systems are more costly and need more equipment . For true diagnosis, the combination of tests may be useful . In this article, we studied a new method, but only one study was conducted for BCGT method in Turkey.…”

Comparison of standard agglutination tests, enzyme immunoassay, and Coombs gel test used in laboratory diagnosis of human brucellosis

“…Alternative methods, such as the enzyme-linked immunosorbent assay (ELISA) and AHG gel test, with which more samples in shorter time periods can be tested, are presented against standardization problems of agglutination tests with the possibility of different evaluations by different people in different laboratories, but evaluation of these tests is necessary before substitution (6)(7)(8)(13)(14)(15)(16).…”

I think of Brucellosis but can not verify: Seronegative Brucellosis

“…Yüksek dilüsyonlu tüp aglütinasyon testi dışında; kültür, polimeraz zincir reaksiyonu (PCR), ELISA, roket immündifüzyon gibi alternatif serolojik testler problemi çözmede yardımcı olmaktadır (13,14). (10,15,16).…”