Variability among commercial batches of normal pooled plasma in lupus anticoagulant testing

Abstract

Introduction Lupus anticoagulant (LA) testing requires normal pooled plasma (NPP) in performing mixing studies and can be used for normalized ratios of clotting times (CTs). The aims were to demonstrate whether significant differences in clotting times between two batches of a same commercial NPP (CRYOcheck™) directly affect NPP‐based cut‐off values. Methods Diluted Russell Viper venom time (DRVVT) and activated partial thromboplastin time (aPTT) were used for LA testing. Screening, mixing and confirm tests were performed with Stago® instruments and reagents. Two batches of commercial NPP (A1291 and A1301 from CRYOcheck™; frozen) were compared in the determination of cut‐off values. Cut‐off values were defined as 99th percentile values of 60 healthy donors and compared with Mann–Whitney U test. Results Cut‐off values obtained with the two NPP batches were significantly different for DRVVT (screen normalized ratio: 1.09 vs. 1.24, screen mix: 41.9 s vs. 38.9 s; index of circulating anticoagulant: 5.0 vs. 8.4; all had p‐value <.001). On the contrary, no significant differences were observed for aPTT (screen normalized ratio: 1.32 vs. 1.34; p‐value = .4068, screen mix: 37.8 s vs. 38.1 s; p‐value = .1153) except for index of circulating anticoagulant: 9.6 versus 10.4 (p‐value <.05). Conclusion This study demonstrates that differences between two commercial NPP batches produced by a same manufacturer influenced LA cut‐off values used for mixing studies and normalized ratios. Adequate cut‐off setting, taking into account NPP CTs, is important to provide accurate conclusion about the presence or absence of a LA and avoid potential clinical impact.

Performance characteristics of 5 numerical indexes in mixing test interpretation under coexistence of lupus anticoagulant and coagulation factor deficiency

“…The mix ratios of the test plasma to NPP were 1:1, 4:1, and 1:4, as described in previous studies [ 1 , 4 , 5 ]. This study introduced 5 indexes to interpret the mixing test results: ICA, mixing test normalized ratio, 1:1 and 4:1 percent corrections, and Mix–NPP ( Table 1 ), in which the cutoff values were followed as described in previous studies [ 1 , 5 , 6 , 15 ].…”

Reassessment of dextran sulfate in anti-Xa assay for unfractionated heparin laboratory monitoring

“…Conversely, in accordance with its usual laboratory use, hexadimethrine bromide was used at a constant concentration of 25 μg/mL [ 22 , [28] , [29] , [30] , [31] ]. The NPP used in this study was frozen platelet-poor plasma (PPP) constituted by plasmapheresis from a minimum of 20 healthy donors mixed in HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) buffer (CRYOcheck) [ 32 ]. The same batch (A1301) was used for all the study.…”

Analytical dilemmas in lupus anticoagulant detection

“…This approach uses the NPP as a marker of on-the-day analytical system performance, from which the patient result is derived via the ratio calculation. An under-appreciated disadvantage of normalizing against NPP values is that different NPP preparations, or even different batches of the same preparation, do not necessarily generate the same clotting times with a given reagent, or with different reagents of the same test type [20,[76][77][78]. The greater the distance of the clotting time of a given NPP from the assay and analyser-specific reference interval (RI) mean clotting time, the greater the likelihood of systematic bias towards false-positive or false-negative ratios [20,74,77,78].…”

“…An under-appreciated disadvantage of normalizing against NPP values is that different NPP preparations, or even different batches of the same preparation, do not necessarily generate the same clotting times with a given reagent, or with different reagents of the same test type [20,[76][77][78]. The greater the distance of the clotting time of a given NPP from the assay and analyser-specific reference interval (RI) mean clotting time, the greater the likelihood of systematic bias towards false-positive or false-negative ratios [20,74,77,78]. In that respect, in the same way that a locally derived, fixed geometric mean normal PT is used in the calculation of the international normalized ratio for VKA monitoring [79], a local reagent and analyser-specific RI mean clotting time is a viable alternative for the denominator in LA assay ratios [14,20,28,70,75,77,[80][81][82].…”