Genotype phenotype association in a large cohort of subjects with protein C or protein S deficiency
L. Böff1, F. Bergmann2, A. Czwalinna2, C. Heller1, M. Krause3, W. Miesbach1, S. Körber1, E. Seifried1, C. Geisen1 (1Frankfurt / Main, Germany, 2Hannover, Germany, 3Wiesbaden, Germany)
Time: 08:00 - 09:15
Objective: Hereditary deficiencies of natural anticoagulant proteins including protein C (PC) and protein S (PS) are known causes of inherited thrombophilia. We aimed to assess the performance of genetic analysis of PROC and PROS1 with relation to PC and PS assay data.
Methods: In a retrospective cohort study we genotyped 314 subjects with PC and 460 subjects with PS deficiency. Mutations were detected by direct sequencing of the coding regions including splice sites of PROC and PROS1. We performed multiplex ligation dependent probe amplification in order to reveal large copy number variations. PC and PS assay data were provided by external centres. Statistic methods of logistic regression and receiver operating characteristic curve analysis were applied to evaluate the correlation between laboratory status and inherited deficiencies and to propose cut-off values for the indication of genetic testing.
Results: Mutations were identified in 226 patients of the PC and 197 patients of the PS deficiency cohort, correlating with an overall mutation detection rate (MDR) for PROC of 72% and PROS1 of 43%, respectively. Both cohorts had a similar mutation profile with the highest prevalence for missense mutations (81% in PC, 60% in PS). MDR correlated negatively with PC and PS levels. In addition, we observed a clear correlation between laboratory data and the type of mutation. For PC activity we determined a cut-off value of 61% with a sensitivity of 81% and a specificity of 64% for revealing a causal gene mutation. Within the PS cohort factor V Leiden (FVL) showed a significant influence on MDR. For individuals without FVL the proposed cut-off value for PS activity is 45% associated with a sensitivity of 70% and a specificity of 65%. In states of acquired reduction due to vitamin K antagonist intake or pregnancy lower cut-off values for PC (44%) and PS (21%) were calculated.
Conclusion: Our findings suggest that in patients with PC activity below 61% and PS levels (activity or free antigen) below 45% genetic analysis represents a useful diagnostic tool to confirm inherited PC and PS deficiency. In addition, in the presence of FVL and acquired deficiency states adjusted cut-off values might be applied.