Validation of Nijmegen-Bethesda assay modifications to allow inhibitor measurement during replacement therapy and facilitate inhibitor surveillance. J Thromb Haemost 2012 Jun;10(6):1055-61
Date
03/23/2012Pubmed ID
22435927Pubmed Central ID
PMC4477703DOI
10.1111/j.1538-7836.2012.04705.xScopus ID
2-s2.0-84861673289 (requires institutional sign-in at Scopus site) 100 CitationsAbstract
BACKGROUND: As part of a pilot U.S. inhibitor surveillance project initiated at the Centers for Disease Control and Prevention (CDC) in 2006, a centralized inhibitor measurement was instituted.
OBJECTIVE: To validate a modified method for inhibitor measurement suitable for surveillance of treated and untreated patients.
METHODS/RESULTS: In all, 710 subjects with hemophilia A were enrolled; 122 had a history of inhibitor (HI). Nijmegen-Bethesda assay (NBA) results on 50 split specimens shipped on cold packs and frozen were equivalent (r=0.998). Because 55% of 228 initial specimens had factor (F)VIII activity (VIII:C) present, a heat treatment step was added. Heating specimens to 56°C for 30 min and centrifuging removed FVIII, as demonstrated by a reduction of VIII:C and FVIII antigen to <1 U dL(-1) in recently treated patients. Among specimens inhibitor-negative before heating, one of 159 with negative HI and five of 30 with positive HI rose to ≥ 0.5 Nijmegen-Bethesda units (NBU) after heating. Correlation of heated and unheated inhibitor-positive specimens was 0.94 (P=0.0001). The modified method had a coefficient of variation (CV) for a 1 NBU positive control of 10.3% and for the negative control of 9.8%. Based on results on 710 enrollment specimens, a positive CDC inhibitor was defined as ≥ 0.5 NBU. Results were similar when 643 post-enrollment specimens were included. Of 160 enrolled hemophilia B patients, two had HI. All others had NBU ≤ 0.2 at enrollment.
CONCLUSION: The CDC experience demonstrates that this modified NBA can be standardized to be within acceptable limits for clinical tests and can be used for national surveillance.
Author List
Miller CH, Platt SJ, Rice AS, Kelly F, Soucie JM, Hemophilia Inhibitor Research Study InvestigatorsMESH terms used to index this publication - Major topics in bold
AntibodiesAntigen-Antibody Reactions
Artifacts
Blood Coagulation Tests
Calibration
Coagulants
Drug Monitoring
Enzyme-Linked Immunosorbent Assay
Factor VIII
Hemophilia A
Hemophilia B
Hot Temperature
Humans
Predictive Value of Tests
Prospective Studies
Protein Denaturation
Reference Standards
Reproducibility of Results
Severity of Illness Index
Time Factors
Treatment Outcome
United States
