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Impact of the variability between normal pooled plasma batches on normalized ratio and mixing time reference cut-off values in lupus anticoagulant testing

1Université catholique de Louvain, CHU UCL Namur, Yvoir, Namur, Belgium, 2Qualiblood s.a., Namur, Namur, Belgium, 3CHU UCL Namur, Yvoir, Namur, Belgium, 4CHU UCL Namur, yvoir, Namur, Belgium, 5Université catholique de Louvain, CHU UCL Namur, Namur Thrombosis and Hemostasis Center (NTHC), Hematology Laboratory, Namur Research Institute for Life Sciences (NARILIS), Yvoir, Belgium, Yvoir, Namur, Belgium

Abstract Number: PB1062

Meeting: ISTH 2022 Congress

Theme: Diagnostics and OMICs » Laboratory Diagnostics

Background: Following ISTH guidelines for lupus anticoagulant testing, Normal Pooled Plasmas (NPPs) should be used for mixing studies and calculation of normalized ratios. The implementation of normalized ratios is assumed to reduce intra-laboratory variability while mixing studies increase lupus anticoagulant diagnosis efficiency. Our current hypothesis is that different batches of a same commercial frozen NPP (Cryocheck®) may show significant variability in clotting times and therefore impact NPP-related reference cut-offs.

Aims: The objective of this study was to demonstrate that significant differences of clotting times between different batches of a same commercial frozen NPP (Cryocheck®) directly affect reference normalized ratios as well as reference mixing (1:1) clotting times.

Methods: Dilute Russell Viper Venom Time (DRVVT) and Activated Partial Thromboplastin Time (APTT) pathways were explored for lupus anticoagulant evaluation. Screening, mixing and confirm tests were performed with Stago® instruments and reagents. Two different batches (NPP 1291 and 1301 from Cryocheck®) were compared in the determination of reference cut-off values with 60 healthy donors (plasmas stored less than 3 years at -80°C). Reference cut-off values were defined as 99th percentile values according to a nonparametric approach. Differences between reference cut-off values were assessed by Mann-Whitney test.

Results: Reference cut-off values obtained with two different NPP batches were significantly different for DRVVT system, reflecting the variability of NPPs clotting times. On the contrary, no significant difference was observed in APTT system (see Table 1).

Conclusion(s): This study has proved that differences between NPP batches may influence lupus anticoagulant reference values that directly depend on NPP clotting times such as normalized ratios and mixing studies. Comparing any new NPP batch to the former one would be useful in the decision of reviewing reference cut-off values. Adequate cut-off values, taking into account NPP clotting time, are important to provide accurate conclusion about the presence or absence of a lupus anticoagulant.

Table

Comparison of reference cut-off values derived from two different NPP batches -NPP 1291 and NPP 1301-.

To cite this abstract in AMA style:

Cabo J, Soleimani R, Morimont L, Baudar J, Guldenpfennig M, Douxfils J, Mullier F. Impact of the variability between normal pooled plasma batches on normalized ratio and mixing time reference cut-off values in lupus anticoagulant testing [abstract]. https://abstracts.isth.org/abstract/impact-of-the-variability-between-normal-pooled-plasma-batches-on-normalized-ratio-and-mixing-time-reference-cut-off-values-in-lupus-anticoagulant-testing/. Accessed October 1, 2023.

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