U.S. Inhibitor Pilot Project: Participant Characteristics and Infusion Log Adherence.

Inhibitors are now considered to be the most important complication of clotting factor replacement therapy in hemophilia. In January 2005, the Universal Data Collection (UDC) project, which includes data on over 14,000 patients with hemophilia A or B, was amended to include prospective data collection on inhibitors. We report interim results of a pilot project involving 9 selected Hemophilia Treatment Centers in the U.S. Dedicated data managers collected risk factor and product exposure data from enrolled patients on a monthly basis. Tracked infusion log submissions were used to estimate patient adherence to infusion log completion. A blood specimen is collected at baseline, annually, at product switch, or for clinical indication and is tested centrally for inhibitor using the Nijmegen modification method. Results are reported and any above a threshold value are followed up with repeat testing and clinical correlation. As of August 2007, 514 male patients with hemophilia, ages 2–84 years (mean 23 yrs SD 17) had been enrolled. Of these, 415 (81%) had FVIII deficiency (64% severe, 20% moderate, 16% mild) and 99 (19%) had FIX deficiency (35%, 43%, and 22%, respectively). 85% of the patients were caucasian, 8% black, and 4% Hispanic. A previous history of inhibitor was present at enrollment in 71 (14%). Prophylactic treatment was used by 37% and 80% received product by home infusion. Historical exposure to product collected at enrollment was as follows: 14% had 0–20 exposure days (ED), 12% had 21–100 ED, 7% had 101–150 ED, and 64% > 150 ED. During follow-up, 6 patients have had inhibitor titer measurements over 0.4 BU. One of these was known to have an active inhibitor at enrollment. Confirmatory testing of remaining cases is underway. Mean adherence rate for patient infusion log completion in the 9 HTC’s was 45% (range 7% to 74%). Overall adherence increased with time on study from about 40% at one month to nearly 60% for those enrolled at least 10 months. In summary, enrolled participants represent a wide range of characteristics including age, race, disease severity and number of factor exposures. Interim findings indicate that prospective collection of factor infusion data from hemophilia patients necessary to appropriately monitor inhibitor formation, is feasible but labor intensive and requires patient adherence to completion and submission of accurate infusion logs. Because inhibitor formation is rare and the potential risk factors are many, large scale studies with long-term follow-up will be needed to fully assess risk factors for inhibitors.