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Sensitivity, specificity and predictive value of modified assays for activated protein C resistance in children
G Brandt1, R Gruppo, C J Glueck
1The Division of Hematology/Oncology, S. Illinois University School of Medicine, Springfield, USA.
Insights
Modified activated partial thromboplastin time (aPTT)-based assays for activated protein C (APC) resistance show high clinical utility in children. Prediluting samples in factor V deficient plasma improves concordance with DNA testing for factor V Leiden mutation.
Area of Science:
- Pediatric Hematology
- Thrombosis and Hemostasis
- Molecular Diagnostics
Background:
- The factor V Leiden mutation is a common inherited thrombophilia.
- Assessing activated protein C (APC) resistance is crucial for identifying thrombophilia risk.
- Limited data exists on the clinical utility of coagulation-based APC resistance assays versus DNA testing in children.
Purpose of the Study:
- To evaluate the clinical utility of four aPTT-based APC resistance assays in pediatric patients.
- To compare the diagnostic performance of these assays against DNA-based factor V Leiden mutation analysis.
Main Methods:
- 169 children (3 months–16 years) were included.
- Four aPTT-based APC resistance assays were performed: APC-SR, n-APC-SR, FDAPC-SR, and n-FDAPC-SR.
- Results were compared with DNA-based PCR for the factor V Leiden mutation (Arg506 to Gln).
- Two modified assays (FDAPC-SR, n-FDAPC-SR) involved prediluting patient plasma in factor V deficient plasma.
Main Results:
- The prevalence of the factor V Leiden mutation was 4.1% (7/169).
- Standard APC resistance assays (APC-SR, n-APC-SR) showed poor concordance with PCR (sensitivity 29% and 57%).
- Modified assays (FDAPC-SR, n-FDAPC-SR) demonstrated excellent concordance (100% sensitivity).
- FDAPC-SR and n-FDAPC-SR showed high predictive values (1.00 and 0.88) and excellent discrimination.
Conclusions:
- Modified aPTT-based APC resistance assays, particularly FDAPC-SR and n-FDAPC-SR, offer high clinical utility in children.
- Predilution in factor V deficient plasma significantly enhances the accuracy of APC resistance testing.
- These modified assays provide reliable identification of the factor V Leiden mutation in pediatric populations.
Abstract:
Very little data is available assessing the clinical utility of coagulation-based APC resistance assays compared to DNA-based analysis for the factor V Leiden mutation in children. Therefore, the clinical utility of four aPTT-based assays for APC resistance was evaluated in 169 children, ages 3 months through 16 years. The prevalence of the Arg506 to Gln mutation was 7/169 (4.1%). Using cutoff points derived from the normal PCR-screened population (n = 162), two assays for APC resistance (APC-SR and n-APC-SR) gave poor concordance with the PCR assay (sensitivity 29% and 57%, respectively). Two modified assays (FDAPC-SR and n-FDAPC-SR), in which patient plasma was prediluted 1:5 in factor V deficient plasma, gave excellent concordance (sensitivity 100%). The predictive value of a positive test was 0.25, 0.44, 1.00 and 0.88 for the APC-SR, n-APC-SR, FDAPC-SR and n-FDAPC-SR, respectively. The FDAPC-SR and n-FDAPC-SR tests gave excellent discrimination using cutoff values derived from the total population (n = 169) without regard to previous PCR screening results.