Marc S. Williams

Pharmacogenetic testing of CYP2C9 and VKORC1 alleles for warfarin

Disclaimer: American College of Medical Genetics statements and guidelines are designed primarily as an educational resource for medical geneticists and other health care professionals to help them provide quality medical genetic services. Adherence to these standards and guidelines does not necessarily ensure a successful medical outcome. These statements and guidelines should not be considered inclusive of all proper procedures and tests or exclusive of other procedures and tests that are reasonably directed to obtaining the same results. In determining the propriety of any specific procedure or test, the health care professional should apply his or her own professional judgment to the specific clinical circumstances presented by the individual patient or specimen. It may be prudent, however, to document in the patients record the rationale for any significant deviation from these standards and guidelines.Warfarin (Coumadin) is a potent drug that when used judiciously and monitored closely, leads to substantial reductions in morbidity and mortality from thromboembolic events. However, even with careful monitoring, initiation of warfarin dosing is associated with highly variable responses between individuals and challenges achieving and maintaining levels within the narrow therapeutic range that can lead to adverse drug events. Variants of two genes, CYP2C9 and VKORC1, account for 30–50% of the variability in dosing of warfarin; thus, many believe that testing of these genes will aid in warfarin dosing recommendations. Evidence about this test is evolving rapidly, as is its translation into clinical practice. In an effort to address this situation, a multidisciplinary expert group was organized in November 2006 to evaluate the role of CYP2C9 and VKORC1 testing in altering warfarin-related therapeutic goals and reduction of adverse drug events. A recently completed Rapid-ACCE (Analytical, Clinical Validity, Clinical Utility, and Ethical, Legal, and Social Implications) Review, commissioned to inform this work group, was the foundation for this analysis. From this effort, specific recommendations for the appropriate use of CYP2C9 and VKORC1 testing were developed and are presented here. The group determined that the analytical validity of these tests has been met, and there is strong evidence to support association between these genetic variants and therapeutic dose of warfarin. However, there is insufficient evidence, at this time, to recommend for or against routine CYP2C9 and VKORC1 testing in warfarin-naive patients. Prospective clinical trials are needed that provide direct evidence of the benefits, disadvantages, and costs associated with this testing in the setting of initial warfarin dosing. Although the routine use of warfarin genotyping is not endorsed by this work group at this time, in certain situations, CYP2C9 and VKORC1 testing may be useful, and warranted, in determining the cause of unusual therapeutic responses to warfarin therapy.

Population-based family-history-specific risks for colorectal cancer: a constellation approach

BACKGROUND & AIMSnColorectal cancer (CRC) risk estimates based on family history typically include only close relatives. We report familial relative risk (FRR) in probands with various combinations, or constellations, of affected relatives, extending to third-degree.nnnMETHODSnA population-based resource that includes a computerized genealogy linked to statewide cancer records was used to identify genetic relationships among CRC cases and their first-, second-, and third-degree relatives (FDRs, SDRs, and TDRs). FRRs were estimated by comparing the observed number of affected persons with a particular family history constellation to the expected number, based on cohort-specific CRC rates.nnnRESULTSnA total of 2,327,327 persons included in > or =3 generation family histories were analyzed; 10,556 had a diagnosis of CRC. The FRR for CRC in persons with > or =1 affected FDR = 2.05 (95% CI, 1.96-2.14), consistent with published estimates. In the absence of a positive first-degree family history, considering both affected SDRs and TDRs, only 1 constellation had an FRR estimate that was significantly >1.0 (0 affected FDRs, 1 affected SDR, 2 affected TDRs; FRR = 1.33; 95% CI, 1.13-1.55). The FRR for persons with 1 affected FDR, 1 affected SDR, and 0 affected TDRs was 1.88 (95% CI, 1.59-2.20), increasing to FRR = 3.28 (95% CI, 2.44-4.31) for probands with 1 affected FDR, 1 affected SDR, and > or =3 affected TDRs.nnnCONCLUSIONSnIncreased numbers of affected FDRs influences risk much more than affected SDRs or TDRs. However, when combined with a positive first-degree family history, a positive second- and third-degree family history can significantly increase risk.

A Policy Model to Evaluate the Benefits, Risks and Costs of Warfarin Pharmacogenomic Testing

AbstractBackground: In 2007, the US FDA added information about pharmacogenomics to the warfarin label based on the influence of the CYP2C9 and VKORC1 genes on anticoagulation-related outcomes. Payers will be facing increasing demand for coverage decisions regarding this technology, but the potential clinical and economic impacts of testing are not clear.n Objective: To develop a policy model to evaluate the potential outcomes of warfarin pharmacogenomic testing based on the most recently available data.n Methods: A decision-analytic Markov model was developed to assess the addition of genetic testing to anticoagulation clinic standard care for a hypothetical cohort of warfarin patients. The model was based on anticoagulation status (international normalized ratio), a common outcome measure in clinical trials that captures both the benefits and risks of warfarin therapy. Initial estimates of testing effects were derived from a recently completed randomized controlled trial (n = 200). Healthcare cost (

Clinician perspectives about molecular genetic testing for heritable conditions and development of a clinician-friendly laboratory report

US, year 2007 values) and health-state utility data were obtained from the literature. The perspective was that of a US third-party payer. Probabilistic and one-way sensitivity analyses were performed to explore the range of plausible results.n Results: The policy model included thromboembolic events (TEs) and bleeding events and was populated by data from the COUMAGEN trial. The rate of bleeding calculated for standard care approximated bleeding rates found in an independent cohort of warfarin patients.According to our model, pharmacogenomic testing provided an absolute reduction in the incidence of bleeds of 0.17%, but an absolute increase in the incidence of TEs of 0.03%. The improvement in QALYs was small, 0.003, with an increase in total cost of

Predicting phenotypic severity of uncertain gene variants in the RET proto-oncogene.

US162 (year 2007 values). The incremental cost-effectiveness ratio (ICER) ranged from testing dominating to standard care dominating, and the ICER was <

The natural history of severe anemia in cartilage-hair hypoplasia.

US50 000 per QALY in 46% of simulations. Results were most sensitive to the cost of genotyping and the effect of genotyping.n Conclusion: Our model, based on initial clinical studies to date, suggests that warfarin pharmacogenomic testing may provide a small clinical benefit with significant uncertainty in economic value. Given the uncertainty in the analysis, further updates will be important as additional clinical data become available.

Familial Clustering of Hemangiomas

The use of molecular genetic tests for heritable conditions is expected to increase in medical settings, where genetic knowledge is often limited. As part of a project to improve the clarity of genetic test result reports to minimize misunderstandings that could compromise patient care, we sought input about format and content from practicing primary care clinicians. In facilitated workgroup discussions, clinicians from pediatric, obstetrics-gynecology, and family practice provided their perspectives about molecular genetic testing with a focus on the laboratory reporting of test results. Common principles for enhancing the readability and comprehension of test result reports were derived from these discussions. These principles address the presentation of patient- and test-specific information, the test result interpretation, and guidance for future steps. Model test result reports for DNA-based cystic fibrosis testing are presented that were developed based on workgroup discussions, previous studies, and professional guidelines. The format of these model test reports, which are applicable to a variety of molecular genetic tests, should be useful for communicating essential information from the laboratory to health care professionals.

Inflammatory bowel disease aggregation in Utah kindreds

Although reported gene variants in the RET oncogene have been directly associated with multiple endocrine neoplasia type 2 and hereditary medullary thyroid carcinoma, other mutations are classified as variants of uncertain significance (VUS) until the associated clinical phenotype is made clear. Currently, some 46 non-synonymous VUS entries exist in curated archives. In the absence of a gold standard method for predicting phenotype outcomes, this follow up study applies feature selected amino acid physical and chemical properties feeding a Bayes classifier to predict disease association of uncertain gene variants into categories of benign and pathogenic. Algorithm performance and VUS predictions were compared to established phylogenetic based mutation prediction algorithms. Curated outcomes and unpublished RET gene variants with known disease association were used to benchmark predictor performance. Reliable classification of RET uncertain gene variants will augment current clinical information of RET mutations and assist in improving prediction algorithms as knowledge increases.

Development, testing, and validation of a patient satisfaction questionnaire for use in the clinical genetics setting

Anemia is seen in over 80% of patients with cartilage‐hair hypoplasia (CHH). While this is usually mild and self‐limited, some patients demonstrate a severe, persistent anemia resembling that seen in Diamond‐Blackfan anemia (DBA). This paper examines the natural history of 12 patients with CHH and severe anemia. Phenotypic features and mutation data (where available) were reviewed, but no significant differences were found that predicted severe anemia. Severe anemia is estimated to occur in approximately 6% of CHH patients and is permanent in more than half of these patients. Thrombocytosis, though not previously reported in CHH, was noted in five patients, similar to that seen in DBA. The role of possible gene–gene and gene–environment interactions is discussed.

Pulmonary disease is a component of distal arthrogryposis type 5

OBJECTIVESnTo assess the degree of relationship among individuals with hemangiomas and to evaluate the relative risk (RR) for family members of individuals with hemangiomas.nnnDESIGNnRetrospective case-control study.nnnSETTINGnUtah Population Database.nnnPARTICIPANTSnData sets of individuals of different ages with International Classification of Diseases, Ninth Revision (ICD-9) codes for hemangiomas were created from sources having medical records linked to the Utah Population Database. Controls were selected who matched cases for sex, birth year, and birthplace inside vs outside of Utah. Ten controls were selected per case, and sampling was performed without replacement. Kinship analysis tools were used to identify pedigrees having excess individuals with hemangiomas.nnnMAIN OUTCOME MEASUREnUsing conditional logistic regression analysis, RR for hemangiomas among several kinship classes was determined.nnnRESULTSnIdentified were 2514 distinct cases 12 years or younger with ICD-9 code 228.01, and the RR for sibs in this group was significantly increased (RR, 2.52; Pxa0<xa0.001). Seventy-three founder families had 5 or more affected descendants with cluster P valuesxa0≤xa0.01; familial standardized incidence ratios ranged from 1.64 to 9.50. Family sizes ranged from 546 to 22xa0291 descendants.nnnCONCLUSIONSnSibs have increased RR for infantile hemangiomas, suggesting a potential genetic contribution to this likely multifactorial disease. Identification of large families with distantly related individuals will be helpful for future shared segment identification analyses.