OC 77.4 - Predicting Bethesda inhibitor titers in Hemophilia A patients on the basis of screening assay results: Ways to economize the Bethesda Assay.

Wednesday, June 28, 2023

11:00 – 11:15 ET

Room: 518

Session Available As: On-Demand

Presenting Author(s)

Dinesh Chandra, MD, DM

Associate Professor
Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
Lucknow, Uttar Pradesh, India

Co-Author(s)

RG

Ruchi Gupta

Additional Professor
sanjay Gandhi PGIMS, Lucknow
Lucknow, Uttar Pradesh, India
PG

Prakhar Gupta

Senior resident
Sanjay Gandhi PGIMS, Lucknow
Lucknow, Uttar Pradesh, India
KR

Khaliqur Rahman

Additional Professor
Sanjay Gandhi PGIMS, Lucknow
Lucknow, Uttar Pradesh, India
sY

sanjeev Yadav

Associate Professor
Sanjay Gandhi PGIMS, Lucknow
Lucknow, Uttar Pradesh, India
MS

Manish Kumar Singh

Assistant Professor
Sanjay Gandhi PGIMS, Lucknow
Lucknow, Uttar Pradesh, India
PM

Prabhakar Mishra

Additional Professor
Sanjay Gandhi PGIMS, Lucknow
Lucknow, Uttar Pradesh, India
JB

Jayanta Kumar Biswas

Laboratory Technician
Sanjay Gandhi PGIMS, Lucknow
Lucknow, Uttar Pradesh, India
RK

Rajesh Kashyap

Professor
Sanjay Gandhi PGIMS, Lucknow
Lucknow, Uttar Pradesh, India

Background: Inhibitory antibodies develop with incidence of approximately 30% among with hemophilia A. Inhibitors are measured by the Bethesda assay, which requires testing for residual FVIII levels in multiple dilutions and in resource constrained settings these assays become prohibitively expensive.

Aims: The study aimed at utilizing the results of inhibitor screening, and values of fresh mix (FM) and incubated mix (IM), to determine/predict the approximate titer of the antibody in a given sample.

Methods: A total 104 samples of hemophilia A with inhibitors were analyzed over a period of 4 years (January 2019 to December 2022). Inhibitor screening and Bethesda assay or the Nijmegen modified Bethesda assay was performed as recommended. The results of prolonged APTT of FM and diffecence between FM and IM were studied and correlated with inhibitor titers. The results of the analysis were then applied prospectively for screening new set of samples.

Results: A concordance in the APTT value of FM and increasing difference between IM and FM increased with rise in inhibitor titers upto 16 BU. However, in higher titers, the difference between IM and FM results decreased. The samples where APTT values of FM were < 50 sec, 51- 60 sec, 60 -70 sec and > 70 sec, the corresponding median inhibitor titers were 3.2BU, 18.4 BU, 27.2 BU and 199.8 BU respectively. Based on these cut-offs, inhibitor assay was performed in 26 new cases. In 68% cases we were able to find the desirable titers in ≤3 dilutions and in remaining 32% cases ≥4 tubes were needed.

Conclusion(s): The inhibitor screening findings and values of FM and IM can be valuable indicators of the expected Bethesda titers. This information can be used to guide the dilution/(s) where residual FVIII assay has to be performed to estimate the Bethesda titer will reduce cost of assay.

Learning Objectives:

To understand the kinetics of inhibitors in a patients Haemophilia A
To predict the inhibitor titres on the basis of the results of inhibitor screening in Haemophilia A
Strategies to reduce the cost of Bethesda assay for inhibitor in Haemophilia A