Long-term course of anti-factor VIII antibody in patients with hemophilia A at a single center.
BACKGROUND
Immune tolerance induction (ITI) can reduce inhibitors against factor VIII concentrates by 70-80%. In this study, we elucidated the characteristics of inhibitors and attempted to determine the proper indications and timing for ITI.


METHODS
Subjects included hemophilia A patients registered at the Korea Hemophilia Foundation from 1991 through 2014. Inhibitors were classified as persistent and transient. Patients were classified into groups according to peak inhibitor titer: low (<2 BU/mL), moderate (2 to <5 BU/mL), high (5 to <10 BU/mL), and very high titer (≥10 BU/mL).


RESULTS
Overall, 350 (21.4%) of 1,634 hemophilia A patients developed inhibitors at least once. Of these, 100 (6.1%) and 250 (15.3%) patients developed persistent and transient inhibitors, respectively. For transient inhibitors, the median peak titer was 1.0 BU/mL, persistent for median of 11.0 months (10.0, 8.0, 13.0, and 19.0 months in the low, moderate, high, and very high titer transient inhibitor groups, respectively). Overall, 95.8% (215), 72.2% (17), 52.4% (21), and 21.7% (97) of patients in the low, moderate, high, and very high titer groups became inhibitor-negative spontaneously, without ITI.


CONCLUSIONS
Given the spontaneous disappearance of inhibitors and high cost of ITI, it is worthwhile to postpone ITI for 11 months unless the peak inhibitor titer is greater than 10 BU/mL.
Korea Hemophilia Foundation, Seoul, Korea.
Ki Young
KY
Yoo
Korea Hemophilia Foundation, Seoul, Korea.
Sang Chun
SC
Joo
Korea Hemophilia Foundation, Seoul, Korea.
Yong Mook
YM
Choi
Hemophilia A; Inhibitor; Longitudinal study