Abstract Number: PB0168
Meeting: ISTH 2020 Congress
Background: The aPTT (activated partial thromboplastin time) test is designed to evaluate the activity of the intrinsic factors. Elongated aPTT may be due to heparin treatment, lack of one of the intrinsic factors, or presence of antibodies against phospholipids, such as Lupus Anti-Coagulant (LAC).
Until now, Instrumentation Laboratory (IL) had a single reagent available for aPTT on the ACL TOP system. This reagent, SynthASil, contains low levels of phospholipids, and is therefore sensitive to the presence of LAC. In cases of prolonged aPTT, we cannot distinguish between the presence of LAC or factor/factors deficiency. Recently, IL adapted an additional reagent for aPTT, SynthAFax, which is rich in phospholipids and therefore is not sensitive to LAC.
Aims: To perform a validation of the SynthAFax reagent, in comparison to SynthASil and Actin FS (Siemens).
Methods: Blood was drawn from 350 subjects in a 3.2% sodium citrate vacuum tube. An aPTT test was done using platelet-poor plasma within four hours, with SynthASil (sensitive to LAC), Actin FS (not sensitive to LAC), and SynthAFax (not sensitive to LAC) on the ACL TOP 750/500.
Results: The reference range of 120 healthy subjects (60 men, 60 women) was 21.2 – 29 sec. (Manufacturer´s reference range is 22.4-32.9 sec.). The repeatability was found to be CV< 1.3% for controls and samples.
aPTT results of subjects lacking LAC were in high correlation between all reagents (SynthAFax vs. Actin FS , R2 = 0.886, SynthAFax vs. SynthASil, R2 = 0.977). 43% (16 out of 37) of subjects who were LAC positive and had prolonged aPTT with SynthASil were corrected to the normal range by Actin FS or SynthAFax.
Conclusions: SynthAFax is highly correlated with the other reagents in subjects negative to LAC. SynthAFax corrects aPTT in some of the LAC positive patients with prolonged aPTT using SynthASil reagent.
To cite this abstract in AMA style:Nakav S, Sulayev Y, Mendez T, Bragg A, Ben-Dor A, Pickholtz I, Kat I. Validation of a Non- Sensitive aPTT Reagent for the Presence of Anti-Phospholipid Abs (Lupus Anti-Coagulant) [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/validation-of-a-non-sensitive-aptt-reagent-for-the-presence-of-anti-phospholipid-abs-lupus-anti-coagulant/. Accessed May 16, 2022.
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