PB0143 - Harnessing the potential of two APTT reagents with different sensitivities for diagnosis of lupus anticoagulant (LA) and its comparison with DRVVT.

Sunday, June 23, 2024

13:45 – 14:45 ICT

Room: Exhibition Hall

Presenting Author(s)

JD

Jasmita Dass, MD, DM

Associate Professor of Hematopathology
All India Institute of Medical Sciences, New Delhi
New Delhi, Delhi, India

Co-Author(s)

Himil Parikh, MD

Senior resident
All India Institute of Medical Sciences, New Delhi
New delhi, Delhi, India
Vandana Puri Tiwari, DR

Senior resident (Academic)
All India Institute of Medical Sciences, New Delhi
New Delhi, Delhi, India
SA

Shreyam Acharya

Senior resident (Academic)
All India Institute of Medical Sciences, New Delhi
New Delhi, Delhi, India
GV

Ganesh Kumar Viswanathan

Associate Professor
All India Institute of Medical Sciences, New Delhi
New Delhi, Delhi, India
RC

Richa Chauhan

Assistant Professor
All India Institute of Medical Sciences, New Delhi
New Delhi, Delhi, India
SK

Suresh Kumar

Senior Technical Officer
All India Institute of Medical Sciences, New Delhi
New Delhi, Delhi, India
MA

Mukul Aggarwal

Assistant Professor
All India Institute of Medical Sciences, New Delhi
Delhi, Delhi, India
PK

Pradeep Kumar

Associate Professor
All India Institute of Medical Sciences, New Delhi
New Delhi, Delhi, India
RD

Rishi Dhawan

Associate professor
All India Institute of Medical Sciences, New Delhi
New Delhi, Delhi, India
TS

Tulika Seth

Professor
All India Institute of Medical Sciences, New Delhi
New Delhi, Delhi, India
MM

Manoranjan Mahapatra

Professor and Head
All India institute of Medical Sciences, New Delhi
New Delhi, Delhi, India

Background: Two test screening strategies are recommended for the diagnosis of lupus anticoagulant (LA) based on Dilute Russell viper venom time (DRVVT) and activated partial thromboplastin time (APTT). Different APTT reagents have varying LA sensitivity and integrated tests are also available.

Aims: To calculate a normalized ratio between clotting times (CT) obtained with the LA- sensitive PTT-LA and a less LA-sensitive CK-Prest reagent (APTT-CK) may represent a valuable APTT-based screening strategy for LA and comparison with DRVVT.

Methods: For determining the cut-off of normalized PTT-LA/ APTT-CK ratio (nLA/CK), plasma from 40 normal subjects was used. A total of 227 plasma samples investigated for LA were included and PTT-LA, nLA/CK, and normalized DRVVT ratio (nDRVVT) were done. All samples showing a prolonged CT on any test underwent 1:1 mixing study and Rosner’s index was calculated. Mix ratios were used for DRVVT if both screen and confirm times were outside laboratory-generated intervals. For nLA/CK, mix ratios were assessed if both PTT-LA and APTT with CK-Prest were outside the reference intervals. Concordance between nLA/CK Ratio, PTT-LA Rosner’s, and nDRVVT ratio was assessed.

Results: Mean±3SD of nLA/CK was 0.75-1.16. nDRVVT ratio (cut-off >1.2) was positive in 80/227 (35.2%) samples while nLA/CK ratio was positive in 74/227 (32.6%). When the mix nLA/CK ratio was also considered, 74/227 (32.6%) samples were positive. For comparison of Rosner’s (cut-off ≥16%), 76/227 (33.5%) samples were positive using PTT-LA, and using DRVVT, positivity declined to 67/227 (29.5%). Chi-square tests comparing the differences between all the tests are shown in Table 1.

Conclusion(s): LA sensitivity of different APTT reagents varies. Calculation of nLA/CK ratio and mixing for prolonged tests is a useful adjunct for LA diagnosis. It represents a simple and sensitive APTT-based integrated strategy for LA screening and can be used as a test for LA where DRVVT is not available.