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SYNOPSISComplex formation between polyacrylic acid (PAA) and bovine serum albumin (BSA), human serum albumin (HSA), hemoglobin (Hb), globin (GI), and, respectively, transferrin (Tr), were studied in neutral water. Water-soluble and insoluble complexes are formed upon addition of divalent copper ions to the solution. T h e contacts between proteins and PAA are achieved via chelate unit formation in which the copper ions are located a t the center. T h e solubility o f t h e polycomplexes depends on the nature of proteins and correlates with their isoelectric points (PI). In the mixtures of Hb-Cu2+-PAA and G1-Cu2+-PAA, insoluble complexes are formed a t p H = PI starting with very low concentrations of Cu2+ (nCu/nAA I 0.01). On the other hand, these polycomplexes remain soluble a t p H > PI. BSA, HSA, and T r form soluble ternary polycomplexes at neutral water (pH 7). T h e formation of the polycomplexes in the mixture BSA-Cu2+-PAA was intensively studied by titration, HPLC, electrophoretic, and spectrophotometric methods. T h e solubility, composition, and stability of these polycomplexes depend on metal/polymer and protein/polymer ratio. Insoluble polycomplexes are formed when concentration of Cu2+ reaches a critical value (ncu/ nAA 2 0.25). At this concentration ofCu*+, phase separation takes place, starting with very low concentration of protein in the system. Over the critical ratio of the protein/polymer, the mixture again exhibits water-soluble character. T h e pattern of distribution of Cu2+ between PAA coils and of protein globules between polymer-metal complex particules appeared t o follow the self-assembly principle. A hypothetical structural scheme for the formation of soluble and insoluble ternary polycomplexes is proposed. 0 1996

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.

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