Usefulness of Huddleson and Rose Bengal tests for detecting anti-Brucella antibodies in occupationally exposed workers from different settings.

WALLACH J; DIAZ R; MORIYON I; TABOADELA C; DELPINO MV; BALDI PC

Inglaterra

Congreso; Brucellosis 2008 International Research Conference (2008); 2008

Although the Rose Bengal test (RB) is the screening test recommended by WHO to detect anti-Brucella antibodies, in Argentina local regulations recommend the use of the Huddleson test for this purpose. The aim of this work was to compare the performance of these tests for detecting individual suspected of brucellosis among occupationally exposed workers in different settings. The study included 106 sera from workers belonging to different risk groups (61 abattoir workers, 28 butchers, 5 cattle breeders, 5 dairy industry employees, 4 meat transporters, 2 microbiology laboratory workers, and 1 veterinarian), which were provided by a work safety insurance company. As negative controls, 20 sera from blood bank donors without brucellosis history were also included. The RB was performed with serially diluted sera using the antigen provided by the Central Veterinary Laboratory of Weybridge. Huddleson tests were performed in different clinical laboratories from Argentina using commercial reagents. Serum agglutination test (SAT) and Coomb’s test, used as confirmatory techniques, were performed by the microplate method described by Rubio et al. Additionally, a radial immunodifussion (RID) with Bucella cytosolic proteins was performed as described by Diaz et al. For each patient, the results of the RB and Huddleson tests were analyzed in the context of epidemiological and clinical data, and the results of confirmatory tests. Seventeen (16%) of the 106 sera from risk groups employees were positive by RB. From these, only 2 (12%) exhibited titers equal or higher than 8, which have been previously shown to indicate a high probability of active infection (Diaz et al., 1st International Meeting on the Treatment of Human Brucellosis, Ioannina, Greece). Seven of the 17 RB positive workers (41%) had previous history of brucellosis. Notably, a subject with a high RB titer (128) did not refer previous brucellosis. Huddleson test results from 103 workers were available. Positive results were informed in 10 cases (9.7%), from which 6 (60%) had previous history of brucellosis. All positive samples by Huddleson were also positive by RB. However, Huddleson test was negative in 6 workers with positive RB. In these 6 discrepant cases, confirmatory tests (SAT and Coombs) exhibited positive results. In the 2 risk groups with a significant number of cases (abattoir workers and butchers) prevalences of anti-Brucella antibodies were 18% and 7%, respectively. Notably, an abattoir worker without brucellosis history exhibited the highest titers in Huddleson, RB, SAT and Coombs tests and was the only case with positive RID. These results suggest that RB is more sensitive than Huddleson for detecting anti-Brucella antibodies in occupationally exposed subjects. Moreover, in discrepant cases, the results of confirmatory tests (SAT and Coombs) agreed with those of RB. Titers higher than 8 in RB correlated with serological results suggestive of active brucellosis. However, a thorough clinical examination and bacteriological studies should be performed to confirm the diagnosis. RB seems to be a better tool for screening purposes, and a recommendation should be made to replace Huddleson with RB in countries in which the former is used for screening.