Evaluation of the Roche LightCycler: a simple and rapid method for direct detection of factor V Leiden and prothrombin G20210A genotypes from blood samples without the need for DNA extraction

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.

Simultaneous and sensitive detection of two pathogenic genes of thrombotic diseases using SPRi sensor with one-step fixation probe by a poly-adenine oligonucleotide approach

Single-base mutations of Factor V Leiden G1691A and Prothrombin gene G20210A are the main genetic risk factors for inherited thrombotic tendency. The establishment for rapid and efficient detection method is of great significance to the prevention of venous thrombosis. In this work, a multiplexed, highly sensitive and regenerable surface plasmon resonance imaging (SPRi) sensor is described to identify and detect the two pathogenic genes by fixing probes in one-step. The probes are fixed by ployA, which is a simpler, faster and lower cost modification method compared with traditional thiol (-SH). PolyA-DNA-AuNPs is used to amplify the signal to improve sensitivity. The detection limit of the sensor is 8 pM, and it has a wide dynamic range between 8 pM and 100 nM and a good linear relationship between 8 pM to 50 pM. The equilibrium dissociation constant (KD) of 3.0 (± 0.3) pM indicates a high binding capacity. Based on the advantages of high-throughput detection, the SPRi chip can simultaneously identify and detect two genes related to thrombotic Diseases. In addition, more than 90% signal intensity can still be obtained on the surface of the chip after being regenerated of 25 times, indicating that this SPRi sensor has good stability and reproducibility. The established SPRi sensor has the advantages of high-throughput, high-sensitivity, label-free and no need for amplification, which is expected to become an effective technical means for real-time online detection of gene point mutations, and can be extended to detect and quantify a wider range of DNA mutation diseases.

Label-Free Oligonucleotide-Based SPR Biosensor for the Detection of the Gene Mutation Causing Prothrombin-Related Thrombophilia

Prothrombin-related thrombophilia is a genetic disorder produced by a substitution of a single DNA base pair, replacing guanine with adenine, and is detected mainly by polymerase chain reaction (PCR). A suitable alternative that could detect the single point mutation without requiring sample amplification is the surface plasmon resonance (SPR) technique. SPR biosensors are of great interest: they offer a platform to monitor biomolecular interactions, are highly selective, and enable rapid analysis in real time. Oligonucleotide-based SPR biosensors can be used to differentiate complementary sequences from partially complementary or noncomplementary strands. In this work, a glass chip covered with an ultrathin (50 nm) gold film was modified with oligonucleotide strands complementary to the mutated or normal (nonmutated) DNA responsible for prothrombin-related thrombophilia, forming two detection platforms called mutated thrombophilia (MT) biosensor and normal thrombophilia (NT) biosensor. The results show that the hybridization response is obtained in 30 min, label free and with high reproducibility. The sensitivity obtained in both systems was approximately 4 ΔμRIU/nM. The dissociation constant and limits of detection calculated were 12.2 nM and 20 pM (3 fmol), respectively, for the MT biosensor, and 8.5 nM and 30 pM (4.5 fmol) for the NT biosensor. The two biosensors selectively recognize their complementary strand (mutated or normal) in buffer solution. In addition, each platform can be reused up to 24 times when the surface is regenerated with HCl. This work contributes to the design of the first SPR biosensor for the detection of prothrombin-related thrombophilia based on oligonucleotides with single point mutations, label-free and without the need to apply an amplification method.

Evolving methods for single nucleotide polymorphism detection: Factor V Leiden mutation detection

BACKGROUND

The many techniques used to diagnose the Factor V Leiden (FVL) mutation, the most common hereditary hypercoagulation disorder in Eurasians, and the most frequently requested genetic test reflect the evolving strategies in protein and DNA diagnosis.

METHODS

Here, molecular methods to diagnose the FVL mutation are discussed.

RESULTS

Protein-based detection assays include the conventional functional activated protein C resistance coagulation test and the recently reported antibody-mediated sensor detection; and DNA-based assays include approaches that use electrophoretic fractionation e.g., restriction fragment length polymorphism, denaturing gradient gel electrophoresis, and single-stranded conformational PCR analysis, DNA hybridization (e.g., microarrays), DNA polymerase-based assays, e.g., extension reactions, fluorescence polarization template-directed dye-terminator incorporation, PCR assays (e.g., amplification-refractory mutation system, melting curve analysis using real-time quantitative PCR, and helicase-dependent amplification), DNA sequencing (e.g., direct sequencing, pyrosequencing), cleavase-based Invader assay and ligase-based assays (e.g., oligonucleotide ligation assay and ligase-mediated rolling circle amplification).

CONCLUSION

The method chosen by a laboratory to diagnose FVL not only depends on the available technical expertise and equipment, but also the type, variety, and extent of other genetic disorders being diagnosed.

Detection of Factor V Leiden and prothrombin c.20210G>A allele by Roche Diagnostics LightCycler®

Venous thrombosis affects one in one thousand people each year, and in many countries, it is a major cause of morbidity and death in hospitalised patients. Factor V Leiden and the prothrombin c.20210G>A transition are relatively common in the Western World, and both increase the risk of venous thrombosis. The author describes the detection of t+++hese two genetic variants on the carousel-based Roche LightCycler®. This simple method has high sensitivity for DNA, making it possible to test blood samples without the need for traditional DNA extraction and purification.

Analytic validity of genetic tests to identify factor V Leiden and prothrombin G20210A

The objective of this study is to systematically review methods for detecting Factor V Leiden or prothrombin G20210A. English-language literature from MEDLINE, EMBASE, The Cochrane Library, the Cumulative Index to Nursing and Allied Health Literature, PsycInfo(c), 2000-December 2008. Studies assessed methods for detection of these mutations in at least 10 human blood samples and reported concordance, discordance, or reproducibility. Two investigators abstracted data on the sample selection criteria, test operators, DNA extraction, experimental test, reference standard, commercial instruments, concordance rates, explanation of any discordance, and whether discordance resolved after repetition. We assessed strength of the evidence using the GRADE criteria. We reviewed 7,777 titles and included 66 articles. The majority of the reviewed studies used PCR-RFLP or AS-PCR as the reference standard. The studies demonstrated that commercially available and precommercial tests have high analytic validity with all having greater than 99% concordance with the reference standard. With a few exceptions, discordance resolved with repetition of the test, suggesting operator or administrative errors were responsible for the discordant results. In the quality assurance studies, greater than 98% of laboratories demonstrated high, even perfect, accuracy when asked to diagnose a sample with a known mutation. The majority of errors came from a limited number of laboratories. Although not all methods may be accurate, there is high-grade evidence that genetic tests for the detection of FVL and prothrombin G20210A have excellent analytic validity. There is high-grade evidence that most, but not all, clinical laboratories test for FVL and prothrombin G20210A accurately.

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.

Quality Assurance Issues and Interpretation of Assays

The consequences of an erroneous thrombophilia diagnosis may be serious if it is used to determine clinical management. Therefore careful selection, assessment, and control of laboratory tests for thrombophilia are essential. As for other coagulation tests, the pre-analytical phase must be carefully controlled with attention to the specific problems associated with each type of assay. The investigator must then recognize that for most laboratory tests of thrombophilia, there are a number of assay types available, often based on different principles of analysis. This creates the potential for different users to obtain varying results depending on the technique employed. Such problems can occur in assays of antithrombin activity, depending on whether the assay employs factor Xa, human thrombin, or bovine thrombin. In clot-based assays of protein C and protein S, there can be specificity problems related to interference by factor V Leiden (FVL), antiphospholipid antibodies, and other substances. Even genetic tests can give erroneous results and should not automatically be seen as absolute without supporting evidence and careful quality-control measures. Whatever technique is selected, it is mandatory to incorporate sufficient concurrent quality-control samples to validate the results of thrombophilia tests. These should include assessment of the parameter at normal and abnormal levels to give confidence in results across the measurement range that would normally be encountered in routine practice. This should be used in conjunction with regular participation in external quality assessment (EQA) (which has been linked to improved laboratory performance in thrombophilia testing). Larger EQA programs can provide information concerning the relative performance of analytical procedures, including the method principle, reagents, and instruments. Herein, we describe many of the methodologic effects in detail. We use specific examples to illustrate the general principle that, in performing laboratory testing for thrombophilia, one must always consider the performance characteristics and limitations of the assay in use.

Fatal spontaneous thrombosis of a cerebral arteriovenous malformation in a young patient with a rare heterozygousprothrombingene mutation

The authors report a case of fatal stroke due to thrombosis of a cerebral arteriovenous malformation (AVM) in a young patient. The patient presented with a progressive severe headache that had lasted for a few days, followed by a rapid deterioration in the level of consciousness. Computed tomography and magnetic resonance imaging were immediately performed, and the images showed a large area of venous ischemia in the left hemisphere as well as a left temporal pial AVM. An emergency decompressive craniectomy was unsuccessful in preventing deterioration in the patient's condition. An autopsy examination revealed a thrombosed AVM leading to a wide area of venous ischemia and massive brain swelling. Thrombophilia investigations identified a heterozygous mutation at position 20209 of the prothrombin gene, a recently reported rare prothrombotic defect. Acute neurological decline after spontaneous thrombosis of an intracranial AVM is rare, and an association with the prothrombin defect in this patient is likely.

Comparative study between the Light Cycler® and the PCR-restriction fragment length polymorphism in detecting factor V Leiden and factor II 20210G>A mutations

OBJECTIVES

To test reproducibility, speed and cost of testing for factor V Leiden and FII 20210G>A in our practice.

DESIGN AND METHODS

We compared conformity, reproducibility, speed and cost using the Light Cycler (LC) and PCR-RFLP.

RESULTS

There was 100% conformity and reproducibility. LC was faster but 23% more expensive per sample. When equipment depreciation and patient expenses are added, LC testing becomes cheaper.

CONCLUSION

In our practice, LC provides fast, reproducible and cost-effective results.

Molecular Genetic Testing of Polymorphisms Associated With Venous Thrombosis

The growing knowledge of genetic polymorphisms predisposing to venous thrombosis has increased the demand for genetic testing of associated risk factors. This has prompted the need for simple, fast, reliable, and cost-effective genotyping methods for identification of those mutations. In the past decade, a large variety of DNA mutation analysis methods have been developed for detection of genetic variants associated with venous thrombosis, including PCR-based and PCR-independent technologies. Each of these technologies possesses unique advantages, but all have a common goal of simplifying and expediting mutation analysis. This review describes some of the commonly used technologies and commercially available platforms employed in clinical laboratories for genetic testing of thrombophilia. The choice of a technology for each individual laboratory would primarily depend on the specific requirements for the assay's accuracy, reliability, speed, throughput, and cost-effectiveness.