Abstract 3185

Introduction:

Lupus anticoagulant (LA) is one of the laboratory criteria for the diagnosis of antiphospholipid syndrome. To detect the presence of LA, ISTH recommends performing two assays based on different principles. Our LA profile includes dilute Russell viper venom time (dRVVT) and two different activated partial thromboplastin time (aPTT) reagents.

The aim of the study was to evaluate sensitivity and specificity of aPTT and dRVVT in women with a history of pre-eclampsia, intra-uterine growth restriction, early recurrent abortion, late fetal loss and placental abruption collectively termed “placenta mediated complications”.

Materials and Methods:

We studied a total of 247 patients and 287 samples in a 10 months period. Based on consensus criteria, samples were retested within a period of three months. 62/247 plasmas samples were collected during pregnancy.

Laboratory studies: Screening tests: aPTT was performed using PTT-LA (Stago) and an aPTT home made reagent with diluted cephalin. dRVVT was performed using Russel viper venom RVV (Stago) and diluted cephalin. Negative control plasma was prepared according to ISTH LA recommendations for the mixing tests. Confirmatory tests: We performed a home made reagent for platelet neutralization procedure (PNP)-aPTT and dRVVT; Rosner Index and % of Correction as criteria for mixing and confirmatory tests interpretation.

Statistical evaluation was performed by ROC method using EP Evaluator 9.9 software.

Results:

172/287 samples (59.9%) were negative, while 115/287 samples (40.1%) were positive for LA. 44/115 samples (38.26%) were positive for both tests (aPTT and dRVVT), 60/115 samples (52.17 %) were positive only for dRVVT and 11/115 samples (9.57%) were positive only for aPTT.

LA was confirmed in 9/62 pregnant women samples (14.5 %). 7 (11.3%) had abnormal dRVVT, the remaining 2 samples were positive for both tests.

Table for PP–

Assay(UCA)/Cut offSensitivity (SE)Specificity (SP)
aPTT (Cephalin) 0.812/43 seg 57.4 94.8 
aPTT (PTT–LA, Stago) 0.813/42 seg 58.3 91.9 
dRVVT (Cephalin) 0.964/45 seg 87.0 100 
Assay(UCA)/Cut offSensitivity (SE)Specificity (SP)
aPTT (Cephalin) 0.812/43 seg 57.4 94.8 
aPTT (PTT–LA, Stago) 0.813/42 seg 58.3 91.9 
dRVVT (Cephalin) 0.964/45 seg 87.0 100 
View Large
Conclusions:

Our results demonstrated: 1- High prevalence of dRVVT positive plasmas 104/115 (90.43%); 2- Despite showing a low performance regarding sensitivity when compared to dRVVT, both aPTT tests were able to detect LA in 47.83% of the positive studies. 3- According to our experience, considering this initial cohort of selected patients, the use of dRVVT as the first and aPTT as the second screening test may help improve the performance for the diagnosis of LA.

Disclosures:

No relevant conflicts of interest to declare.

Topics:
antiphospholipid syndrome, complications of pregnancy, childbirth and the puerperium, fetal death, activated partial thromboplastin time measurement, dilute russell viper venom time, phosphatidylethanolamines, screening test, abortion, habitual, abruptio placentae, laboratory techniques and procedures

Author notes

*

Asterisk with author names denotes non-ASH members.

© 2010 by The American Society of Hematology
2010
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