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Detection of a common mutation in factor V gene responsible for resistance to activate protein C causing
A Ferreira-Gonzalez1, L M Fisher, C M Lehman
1Department of Pathology, Medical College of VA/VCU, Richmond, Virginia 23298-0248, USA.
Insights
A genetic test for factor V mutation, a cause of hereditary thrombosis, is more sensitive than the COATEST assay. Direct genetic testing is recommended when activated protein C resistance is suspected.
Area of Science:
- Genetics
- Hematology
- Molecular Biology
Background:
- Activated protein C resistance (APCR) is linked to a factor V gene mutation (G1691A).
- This mutation leads to arginine 506 being replaced by glutamine, predisposing individuals to thrombosis.
- Prevalence varies by ethnicity, with higher rates in Caucasians.
Purpose of the Study:
- To evaluate the prevalence of the factor V mutation in different ethnic groups.
- To compare the diagnostic accuracy of RFLP-PCR genetic testing with the COATEST assay for detecting the factor V mutation.
- To determine the optimal diagnostic approach for suspected hereditary predisposition to thrombosis.
Main Methods:
- Restriction Fragment Length Polymorphism-Polymerase Chain Reaction (RFLP-PCR) assay used to detect the factor V G1691A mutation.
- COATEST, a modified partial thromboplastin assay, used for comparison.
- Analysis of 90 patient specimens, with 78 compared between the two methods.
Main Results:
- Factor V mutation prevalence was 3.3% in healthy Caucasians and 1.25% in healthy African-Americans.
- The COATEST assay showed a sensitivity of 50% and specificity of 93% compared to RFLP-PCR.
- Mutation frequency in tested samples was 13.3% for Caucasians and 6.88% for African-Americans.
Conclusions:
- The RFLP-PCR genetic test is a more sensitive and definitive assay for detecting the factor V mutation.
- The COATEST assay's low sensitivity limits its utility for diagnosing factor V mutation.
- Direct genetic testing via RFLP-PCR or equivalent is recommended for suspected hereditary thrombosis due to APCR.
Abstract:
Hereditary predisposition to thrombosis due to activated protein C resistance (APCR) has been attributed to a missense mutation in the factor V gene at nucleotide 1691 (G to A), causing replacement of arginine at codon 506 with glutamine. Using an RFLP-PCR assay to detect this mutation, we measured a prevalence of 3.3% in healthy Caucasians and 1.25% in healthy African-Americans. In addition, we evaluated a total of 90 consecutive specimens submitted to the coagulation laboratory at the Medical College of Virginia for the presence of this mutation. We compared our results for 78 of these specimens with the values measured by a modified partial thromboplastin assay, the COATEST. Twelve of the 90 samples could not be tested using the COATEST because the patients were undergoing anticoagulant therapy. One of the latter 12 specimens was positive by the RFLP-PCR test. Using the genetic test as the definitive assay and the cutoff value established for distinguishing between normal and abnormal results by the COATEST, the COATEST had a sensitivity of 50% and specificity of 93% for the detection of factor V mutation. Analysis of the 90 samples stratified by ethnic groups revealed a frequency of mutation of 13.3% for Caucasians and 6.88% for African-Americans, although with the present sample size, the difference was not statistically significant. Although the COATEST is technically simpler to perform than the genetic test for diagnosing the presence of the factor V mutation, its use for this purpose is limited due to low sensitivity. Thus where this disorder is clinically suspected, submission of the specimen directly for genetic testing by RFLP-PCR or equivalent assay should be considered.