Factor VIII inhibitors are produced during or after coagulation factor VIII (FVIII) therapy in hemophilia A patients. These inhibitors are usually detected by a modified Bethesda assay or an enzymelinked immunosorbent assay (ELISA). In this study, we used the Bethesda assay to determine the incidence of FVIII inhibitors in 75 fresh plasma samples obtained from 50 hemophilia A patients, and then used ELISA and the Bethesda assay to determine the titres of these inhibitors after the samples had been frozen and thawed. The samples from the screening Bethesda assay were centrifuged and stored at -70degrees C in accordance with the assay guidelines. Subsequently, these samples were thawed and analyzed using ELISA and the Bethesda assay. The incidence of inhibitors in hemophilia A patients was 20.0%. Among the 35 inhibitor-positive samples identified in the screening Bethesda assay, 16 were positive in ELISA while only 4 were positive in the repeated Bethesda assay. In this study, the ELISA technique showed a higher sensitivity than the Bethesda assay in the detection of FVIII inhibitors in samples that were subjected to freezing and thawing procedures; this was because the Bethesda assay could not identify the FVIII inhibitors that were degraded after freezing and thawing.
Blood Coagulation Factor Inhibitors/*analysis ; *Enzyme-Linked Immunosorbent Assay ; Factor VIII/*antagonists &inhibitors/metabolism ; Hemophilia A/*blood/diagnosis ; Humans ; Immunologic Tests ; Male

OBJECTIVETo study the current situation of coagulation factor VIII (FVIII) inhibitor development in children with hemophilia A (HA) through a cross-sectional survey, and to explore the risk factors of inhibitor development in order to provide evidence for further prevention and management strategies.

METHODThe clinical data of outpatients with hemophilia A in Beijing Children's Hospital seen from November 2012 to May 2013 were collected, FVIII inhibitor was screened and analyzed its risk factors.

RESULTA total of 102 HA children were enrolled, 5 were mild cases, 32 were moderate, and 65 were severe cases; the median age on enrollment was 55.5 (3.0-200.0) months:19(18.6%) of patients had inhibitors and 9 (8.8%) had low-titer inhibitors, 10 (9.8%) had high-titer inhibitors. Receiving FVIII treatment for life-threatening bleeding (P = 0.03) ,OR 4.10 (95%CI:1.17-14.32) was a risk factor for inhibitor generation and patients within 20 exposure days have more chances of inhibitor development (P = 0.04) ,OR 3.32 (95%CI:1.02-10.86) . High and intense FVIII exposure within short term was the risk factor for high titer inhibitor development (P = 0.01) ,OR 5.25 (95%CI:1.45-21.92) .

CONCLUSIONIntense FVIII exposure for severe hemorrhage was the risk factor of inhibitors development especially of high titer inhibitors.

Adolescent ; Blood Coagulation Factor Inhibitors ; blood ; Child ; Child, Preschool ; Cross-Sectional Studies ; Dose-Response Relationship, Drug ; Factor VIII ; administration & dosage ; antagonists & inhibitors ; Female ; Hemophilia A ; blood ; therapy ; Humans ; Infant ; Male ; Multivariate Analysis ; Risk Factors ; Time Factors