American College of Medical Genetics consensus statement on factor V Leiden mutation testing

The genetic family history as a risk assessment tool in internal medicine

PURPOSE

The study goals were to (1) determine the proportion of unselected individuals at increased risk for diseases with known genetic components and (2) compare the documentation and quality of risk assessment between a questionnaire, a pedigree interview, and chart review.

METHODS

Seventy-eight patients seen in a division of internal medicine were randomized into two groups, which completed a questionnaire or underwent a pedigree interview. Chart notes were compared to both study tools.

RESULTS

Sixty-two (79.5%) of the 78 participants scored at increased risk for at least one category. Either of the two study tools found significantly more people at high risk (48/78, 61.5%) than the chart review (31/78, 39.7%) (P = 0.01).

CONCLUSIONS

Approximately 20% of patients in an unselected internal medicine practice were at an increased risk that was not documented in reviewed chart notes. Targeted family history analysis reveals patients who require increased medical surveillance, preventive measures, or genetic counseling/testing.

Primer on medical genomics. Part VI: Genomics and molecular genetics in clinical practice

An important milestone in medical science is the recent completion of a "working draft" of the human genome sequence. The identification of all human genes and their regulatory regions provides the framework to expedite our understanding of the molecular basis of disease. This advance has also formed the foundation for a broad range of genomic tools that can be applied to medical science. These developments in global gene and gene product analysis as well as targeted molecular genetic testing are destined to change the practice of modern medicine. Despite these exciting advances, many practicing clinicians perceive that the role of molecular genetics, especially that of genomics, is confined primarily to the research arena with little current clinical applicability. The aim of this article is to highlight advances in DNA/RNA-based methods of susceptibility screening, disease diagnosis and prognostication, and prediction of treatment outcome in regard to both drug toxicity and response as they apply to various areas of clinical medicine.

Factor V Leiden protects against blood loss and transfusion after cardiac surgery

BACKGROUND

The outcome of cardiac surgery is influenced by several factors, but the impact of specific genetic variants has not been systematically explored. Because blood conservation is a pressing issue in cardiac surgery, we tested the hypothesis that factor V Leiden (FVL), a common coagulation factor polymorphism, may protect against blood loss and transfusion in patients undergoing cardiac surgery.

METHODS AND RESULTS

We enrolled 517 patients undergoing cardiac surgery, including 26 heterozygous FVL carriers, and evaluated the impact of FVL on chest tube output and transfusion by using univariate and multivariate techniques. For patients with FVL, blood loss at 6 (238+/-131 mL) and 24 hours (522+/-302 mL) was significantly lower than that for noncarriers (358+/-259 mL and 730+/-452 mL; P<0.001 and P=0.001, respectively). In a multivariate regression analysis, controlling for ethnicity and factors known to affect blood loss, FVL was a significant independent contributor at both time points. Using a similar regression approach, FVL did not have a significant effect on the number of units transfused. However, logistic regression of the risk of receiving any transfusion during hospitalization demonstrated a significant independent protective effect of FVL on overall transfusion risk.

CONCLUSIONS

FVL represents a common genetic trait that may protect against blood loss and transfusion in this population. This study demonstrates that genetic variability can affect the outcome of cardiac surgery.

Clinical utility of factor V leiden (R506Q) testing for the diagnosis and management of thromboembolic disorders

OBJECTIVE

To review the current state of the art regarding the role of the clinical laboratory in diagnostic testing for the factor V Leiden (FVL) thrombophilic mutation (and other protein C resistance disorders), and to generate, through literature reviews and opinions of recognized thought-leaders, expert consensus recommendations on methodology and diagnostic, prognostic, and management issues pertaining to clinical FVL testing.

DATA SOURCES, EXTRACTION, AND SYNTHESIS

An initial thorough review of the medical literature and of current best clinical practices by a panel of 4 experts followed by a consensus conference review, editing, and ultimate approval by the majority of a panel of 28 additional coagulation laboratory experts.

CONCLUSIONS

Consensus recommendations were generated for topics of direct clinical relevance, including (1) defining those patients (and family members) who should (and should not) be tested for FVL; (2) defining the preferred FVL laboratory testing methods; and (3) defining the therapeutic, prophylactic, and management ramifications of FVL testing in affected individuals and their family members. As FVL is currently the most common recognized familial thrombophilia, it is hoped that these recommendations will assist laboratorians and clinicians caring for patients (and families) with this common mutation.

Medical genetic test reporting for cystic fibrosis (deltaF508) and factor V Leiden in North American laboratories

PURPOSE

Physicians are ordering an increasing number of genetic tests. Results and additional information provided in the test result report are vital to the physician in making appropriate patient management decisions. Because variability in test result reports can impact patient care, we sought to determine whether variations exist in test reports for cystic fibrosis (CF) and factor V Leiden (fVL) with specific comparison to professional guidelines and recommendations.

METHODS

A cross-sectional study design analyzing for the presence of 16 critical elements in CF reports and 12 critical elements in fVL reports solicited from United States and Canadian laboratories.

RESULTS

Of 44 laboratories performing CF testing and 72 laboratories performing fVL testing, 64% responded. For CF reports, 21% included ethnicity, 64% described methodology, and 61% discussed genetic counseling. For fVL reports, 80% described methodology and 52% discussed the need for genetic counseling in mutation-positive reports.

CONCLUSIONS

Variability exists in report content among North American laboratories performing CF and fVL testing. Many reports lack information deemed critical by professional guidelines and recommendations.

Commercial molecular diagnostics in the U.S.: The Human Genome Project to the clinical laboratory

Molecular diagnosis is the detection of pathogenic mutations in DNA and RNA samples to aid in detection, diagnosis, subclassification, prognosis, and monitoring response to therapy. Principles underlying nucleic-based diagnosis originate from localization, identification, and characterization of genes responsible for human disease. Clinical molecular genetics is now part of the mainstream of medical care in the United States. All commercial clinical reference laboratories now have a molecular genetic diagnostic unit, many of which are in contractual agreement with third party payers to provide services. Gene discovery provides valuable insight into the mechanisms of disease processes and gene-based markers will enable clinicians to study disease predisposition, as well as improved methods for diagnoses, prognosis, and monitoring of therapy. The broad range of mutation spectrum and type performed in the clinical laboratory requires the use of multiple technologies rather than a single typing platform. Platform choice depends on such diverse factors as local expertise, test volume, economies of scale, R&D budget, and royalties. Test validation is a major hurdle and positive control samples are often not readily available. Oversight and the regulatory environment for clinical molecular genetics laboratories in the United States are evolving rapidly. Several government agencies and private organizations are currently involved in revision of specific laboratory standards, including the Secretary's Advisory Committee on Genetic Testing (SACGT), Food and Drug Administration (FDA), Center for Disease Control (CDC), College of American Pathologists (CAP), American College of Medical Genetics (ACMG), and the individual states.