Estimating the cost of redundancy in molecular diagnostics: The case of activated protein C resistance and factor V Leiden

Background: The activated protein C resistance - sensitivity ratio in the presence of Factor V deficient plasma (APC-SR/Factor V) exhibits a high sensitivity for factor V Leiden mutation and has been proposed as the diagnostic approach of choice, as an alternative to genetic tests, to evaluate activated protein C resistance. A survey, including 4969 requests, was performed on the activity of a typical Molecular Diagnostics Laboratory in order to estimate the costs due to reagents, instrumentation and personnel. Methods: The global costs of three hypothetical diagnostic approaches were compared: (A) exclusive molecular test for FV Leiden; (B) APC-SR alone; (C) APC-SR and the exclusive confirmation of positive results with molecular test. Results: The global cost for each patient with the three approaches investigated were respectively 42.20 euros (A), 1.09 euros (B), and 4.33 euros (C). The cost for finding a patient with factor V Leiden mutation was 549.00 euros for A, 14.18 euros for B, and 56.32 euros for C. It was calculated that a decrease of 97.42% and 89.74% can be obtained using the approaches B and C, respectively. The difference in cost between B and C can be justified by the avoidance of false positive cases (6%) and by the impossibility of distinguishing homozygous from heterozygous patients using APC-SR exclusively (B). Conclusions: In the case of suspected phenotype APC resistance, we suggest a laboratory approach, which provides the combined and sequential use of ProCGlobal/FV analysis and a subsequent genetic test for positive patients.