Comparison of the International Immune Tolerance Registry and the North American Immune Tolerance Registry

Two immune tolerance registries--the International Immune Tolerance Study Group (ITSG) and North American Immune Tolerance Study (NAITS) - are compared and findings from combined data reported. The registries differed with respect to data collection tools, location, host and environmental factors, start date distribution and treatment products. The success and failure rates were similar in the two studies. There was a highly significant association between maximum historical titre and immune tolerance success; the success rate decreased as the historical titre increased. There was a significant association between inhibitor titre immediately prior to treatment and the probability for treatment success, and between outcome and time from diagnosis to treatment in the ITSG (of borderline significance in the NAITS). There was a significant association between outcome and dose, though the direction of the associations was not the same. In the ITSG, success was associated with doses greater than or equal to 200 IU/kg/day, while in the NAITS, greater success was observed with doses of less than 50 IU/kg/day. There was no association between outcome and treatment product. Data from the two registries were combined to produce a table for calculating the chance of successful treatment by historical titre, pretreatment titre, and dose.