A Whole Blood, Multiplex PCR Detection Method for Factor V Leiden and the Prothrombin G20210A Variant

Laboratory Diagnosis of Activated Protein C Resistance and Factor V Leiden

The factor V Leiden (FVL) polymorphism is known as the most common inherited risk factor for venous thrombosis. In turn, FVL is the leading cause of an activated protein C resistance (APCR) phenotype, in which the addition of exogenous activated protein C to plasma does not result in the expected anticoagulant effect. In the routine laboratory approach to the formal diagnosis of FVL, an initial positive screening plasma-based method for APCR is often performed, and only if needed, this is followed by a confirmatory DNA-based assay for FVL. Multiple methods with accepted sensitivity and specificity for determining an APCR/FVL phenotype are commonly categorized into two separate groups: (1) screening plasma-based assays, including qualitative functional clot-based assays, for APCR, and (2) confirmatory DNA-based molecular assays, entailing several tests and platforms, including polymerase chain reaction-based and non-PCR-based techniques, for FVL. This review will describe the methodological aspects of each laboratory test and prepare suggestions on the indication of APCR and FVL testing and method selection.

An overview of methods for detection of factor V Leiden and the prothrombin G20210A mutations

Venous thromboembolism, represented by deep venous thrombosis and pulmonary embolism, is a common disease with high mortality and morbidity. Within the last 25 years, risk factors for venous thromboembolism have been linked to mutations in the genes of the coagulation/anticoagulation system. Factor V Leiden and the prothrombin G20210A mutations are the most prevalent inherited risk factors predisposing to venous thromboembolism in the Western world. Tests to detect these mutations are carried out when investigating a personal or family history of venous thromboembolism. At the present, there are several different methods available for the detection of these mutations in the laboratory. The choice of the method will depend on many variables. This article is aimed at reviewing the available methods for the detection of factor V Leiden and prothrombin G20210A mutations, their principle, applicability, advantages and disadvantages of use.

A whole-blood homogeneous assay for the multiplex detection of the factor V G1691A and the prothrombin G20210A mutations

We describe an assay for the simultaneous detection in DNA or whole blood samples of the G1691A (Leiden) mutation in the factor V allele and the G20210A mutation in the prothrombin allele, both of which predispose humans to thrombosis. The assay uses a dual-probe quenching system in which one probe of a pair is labelled with a fluorophore and the adjacent probe is labelled with a fluorescence quencher. The primer partners were present in unequal amounts, and the genotypes were identified by melt curve analysis, which, together with the PCR, was performed in a Rotor-Gene centrifugal thermal cycler. The performance of the assay was assessed by consistency of melting temperature (Tm) values and height of melt curves from within- and between-run analyses. The stability of the PCR reagents and whole blood was assessed by determining Tm and peak height values after storage at -20, 4 degrees C or room temperature. Concentrations of the reaction reagents were finely adjusted to obtain consistent and clearly distinguishable melt curves that facilitated automatic assignment of 43 genotypes comprising wild-type and mutant alleles. The mean (SD) Tms and peak heights of 31 DNA samples assayed in a single run were 54.85 degrees C (0.07) and 2.33 U (0.15) for factor V and 53.69 degrees C (0.19) and 1.5 0U (0.08) for prothrombin. The Tms and melt peak heights for DNA from wild-type individuals (n=10) when assayed for between- and within-run variability showed SDs of <or=0.17 and <or=0.3 for Tm and peak height values, respectively. When whole blood was used as the sample, the assay performance was comparable to that of purified DNA samples, with whole blood assays (n=30) yielding mean (SD) Tms and peak heights of 53.74 degrees C (0.11) and 2.10 U (0.32) for factor V and 53.27 degrees C (0.12) and 2.15 U (0.18) for prothrombin. Reaction reagents stored for 12 months at room temperature produced satisfactory results, as did whole blood stored frozen for 2 years or in mineral oil at room temperature for at least 1 week. The features of the homogeneous PCR assay described in this article should facilitate the use of such assays in clinical laboratories.

Multiplex PCR-RFLP assay for detection of factor V Leiden and prothrombin G20210A

Factor V Leiden and prothrombin G20210A are clinically relevant genetic risk factors for venous thrombosis. Molecular diagnostic testing for factor V Leiden and prothrombin G20210A is widespread, and laboratories use a variety of technical approaches. Here we introduce a multiplex polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) based on single (Mn/l) restriction endonuclease digestion. The assay was shown to simultaneously and accurately detect factor V Leiden and prothrombin G20210A mutations.

Detection of factor V Leiden by PCR-SSCP using GMA precast Elchrom scientific gels

Genetic abnormalities in hemostatic proteins associated with hypercoagulability are an important hereditary risk factor for venous thrombosis. Several genetic mutations that cause hereditary disorders predisposing to thrombosis have been described, point mutation in the coagulation factor V gene (FV:R506Q), called factor V Leiden, being the most common of them. A new inexpensive and simple polymerase chain reaction-single-strand polymorphism (PCR-SSCP) based method for detection of this genetic abnormality is reported. The study population consisted of 150 subjects whose factor V genotype was previously determined by PCR-RFLP method using the Mnl I restriction endonuclease. A 223-bp fragment containing the G1692-A (Arg 506-Gln) polymorphic site in exon 10 of the factor V gene was amplified, denatured, and run overnight on the commercially available GMA gels for SSCP. PCR-SSCP analysis showed reproducible and uniform band patterns for FV mutant and wild type alleles. Furthermore, PCR-SSCP results were consistent with those obtained with PCR-RFLP analysis (100%). The described PCR-SSCP procedure is reliable, time-saving, and cost-effective. The method may be considered as a potentially powerful new tool in the routine detection of factor V Leiden.

Duplex PCR-RFLP for simultaneous detection of factor V Leiden and prothrombin G20210A

The authors have used a primer-engineered duplex polymerase chain reaction (PCR) -restriction fragment length polymorphism (RFLP) for the simultaneous detection of factor V Leiden and prothrombin G20210A mutations. The method involves the generation of HindIII RFLPs, and the restricted amplification products are analyzed by agarose gel electrophoresis in a single gel lane. This method is simple an inexpensive, and readily adaptable to the routine in a clinical molecular diagnostic laboratory other that our own.

DNA technology for the detection of common genetic variants that predispose to thrombophilia

With the identification of common single locus point mutations as risk factors for thrombophilia, many DNA testing methodologies have been described for detecting these variations. Traditionally, functional or immunological testing methods have been used to investigate quantitative anticoagulant deficiencies. However, with the emergence of the genetic variations, factor V Leiden, prothrombin 20210 and, to a lesser extent, the methylene tetrahydrofolate reductase (MTHFR677) and factor V HR2 haplotype, traditional testing methodologies have proved to be less useful and instead DNA technology is more commonly employed in diagnostics. This review considers many of the DNA techniques that have proved to be useful in the detection of common genetic variants that predispose to thrombophilia. Techniques involving gel analysis are used to detect the presence or absence of restriction sites, electrophoretic mobility shifts, as in single strand conformation polymorphism or denaturing gradient gel electrophoresis, and product formation in allele-specific amplification. Such techniques may be sensitive, but are unwielding and often need to be validated objectively. In order to overcome some of the limitations of gel analysis, especially when dealing with larger sample numbers, many alternative detection formats, such as closed tube systems, microplates and microarrays (minisequencing, real-time polymerase chain reaction, and oligonucleotide ligation assays) have been developed. In addition, many of the emerging technologies take advantage of colourimetric or fluorescence detection (including energy transfer) that allows qualitative and quantitative interpretation of results. With the large variety of DNA technologies available, the choice of methodology will depend on several factors including cost and the need for speed, simplicity and robustness.

Analytical evaluation of primer engineered multiplex polymerase chain reaction-restriction fragment length polymorphism for detection of factor V Leiden and prothrombin G20210A

Factor V Leiden and prothrombin G20210A are clinically relevant genetic risk factors for venous thrombosis. Analysis for both mutations is increasingly being performed on patients exhibiting hypercoagulability. The goal of the current study was to evaluate the performance of primer-engineered multiplex polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for the simultaneous detection of factor V Leiden and prothrombin G20210A. Primer-engineered multiplex PCR-RFLP methods for the detection of factor V Leiden and prothrombin G20210A from the medical literature were reviewed. A modified method was optimized in which both mutations generate HindIII RFLPs and the prothrombin amplicon contains an invariant HindIII recognition site to assess the completeness of endonuclease digestion. Digested amplification products were analyzed by agarose gel electrophoresis in a single gel lane and visualized by ethidium bromide. Primer-engineered multiplex PCR-RFLP was used to analyze 205 human genomic DNA samples whose factor V Leiden genotypes had been previously determined by MnlI PCR-RFLP. Complete concordance for factor V Leiden genotypes was observed between the two methods in the 205-sample cohort comprising 139 wild-type, 62 heterozygous mutant, and four homozygous mutant individuals. For prothrombin G20210A, primer-engineered multiplex PCR-RFLP identified 196 wild-type and nine heterozygous mutant individuals in the 205-sample cohort. To independently verify prothrombin genotypes, the nine heterozygous mutants and an additional 11 wild-type patient samples (representing 10% of patient samples) were subjected to DNA sequencing. Complete concordance was observed between DNA sequencing and primer-engineered multiplex PCR-RFLP results. In further validation, 123 of the DNA samples consisting of four heterozygous mutant and 119 wild type individuals were genotyped with the Invader Assay for Factor II (prothrombin G20210A). Results showed 100% concordance between the Invader Assay and primer-engineered multiplex PCR-RFLP. A primer-engineered multiplex PCR-RFLP based on single restriction endonuclease digestion has been evaluated and shown to simultaneously and accurately detect factor V Leiden and prothrombin G20210A mutations. The method is robust and readily adaptable to the clinical molecular diagnostic laboratory.

The methylenetetrahydrofolate reductase gene C677T polymorphism in patients with homozygous sickle cell disease and stroke

Homozygosity for the methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism may cause hyperhomocysteinaemia, a recognized risk factor for stroke, in individuals with folate deficiency. Homozygous sickle cell (SS) disease is associated both with increased demands for folic acid and a tendency to develop stroke. We therefore investigated a possible role of the MTHFR C677T polymorphism in SS disease patients with stroke. Investigation of the frequency of the polymorphism in 48 patients with stroke and in 48 age-, sex- and racially-matched SS controls without stroke failed to reveal a difference between the groups (Fisher exact test, P = 0.99). Homozygosity for the MTHFR C677T polymorphism is unlikely to be a risk factor for stroke in this population with SS disease.