Comparative studies of indirect hemagglutination

Optimal conditions were established for the performance of the tanned-cell, chromium chloride, bis-diazotized benzidine, and tolylene-2,4-diisocyanate hemagglutination tests. Titers of a number of standard antisera were then determined by applicable techniques. With antisera to bovine serum albumin, all four methods gave equal titers while the tannedcell hemagglutination test was shown most sensitive for titrating antisera to rabbit thyroid extract. Variable results were obtained with human thyroid extract, dependent on the individual antiserum tested. In the case of anti-insulin antisera, the most successful assay was achieved with bis-diazotized benzidine. Results were equivalent in most cases whether crystalline or amorphous insulin was used for coating erythrocytes.