From Personalized Medicine

Knowledge, Attitudes and Education of Pharmacists Regarding Pharmacogenetic Testing

Mary W Roederer; Marcia Van Riper; John Valgus; George Knafl; Howard McLeod

Abstract and Introduction

Abstract

Aim: Pharmacists are positioned to provide medication counseling and drug information to patients. This study assessed the knowledge, attitudes and education of over 700 pharmacists concerning pharmacogenetics and pharmacogenetic testing.
Methods: A multiquestion, online survey was developed to assess healthcare provider knowledge, attitudes and education concerning pharmacogenetic testing.
Results: More than 90% of pharmacists were interested in learning more about pharmacogenetics and testing, with those with less than 10 years of experience were more likely to want web-based continuing education programs. The pharmacists were unlikely to have had formalized education regarding pharmacogenetics, were very likely to rate their knowledge accurately, and were more likely to have a positive attitude about pharmacogenetics if they had received education regarding pharmacogenetics.
Conclusion: Most pharmacists were interested in learning more about pharmacogenetic testing.

Introduction

Pharmacists know that one dose does not always fit all. Just as pharmacokinetics helps to find the right dose of gentamicin or vancomycin for a patient, pharmacogenetics is the study of how heritable traits affect an individual's response to a medication. Pharmacogenetic testing utilizes the results of genetic tests to guide a patient's drug therapy, much like renal function and drug levels guide pharmacokinetic dosing of selected drugs.
With adverse drug reactions costing hundreds of thousands of US dollars and drugs causing the desired effect in only a subset of those prescribed the drug, any and all scientific advances that decrease the toxicity or improve the efficacy of prescribed medications is beneficial.^[1–3] Pharmacists, as the chemists of the healthcare team and the drug therapy experts, are poised to take the lead in providing patients and prescribers with the information essential to optimizing pharmacotherapy for treatment and control of diseases and conditions. Pharmacogenetics can be a powerful tool to aid in refining a drug dose or prioritizing one drug over another for a patient. In fact the US FDA requires inclusion of pharmacogenetic information in over 100 drug labels, approximately 10% of all drug labels up to 2005.^[4] Of the drugs reviewed by a major pharmacy benefits manager (PBM; n = 36.1 million patients), approximately 25% of the patients filled prescriptions for drugs with a mention of pharmacogenetics in the drug label.^[4] Astoundingly, pharmacists may see one in four patients fill prescriptions for drugs that have human genomic information in the drug label.
Warfarin is one drug with pharmacogenetic information included in the drug label. Warfarin is metabolized by the polymorphic CYP2C9 enzyme, among other drug-metabolizing enzymes, and targets VKORC1 for drug action. The warfarin drug label states that CYP2C9 and VKORC1 genotype can assist in selecting a starting dose of warfarin and provides a table with a range of doses for each combination of genotype information.^[101] The dosing recommendations based on genotype were added to the drug label for warfarin after studies found that genetic differences in CYP2C9 and VKORC1 affect the dose of warfarin required to achieve the desired therapeutic effect, generally an international normalized ratio of 2–3, or to avoid untoward effects such as bleeding.^[5,6] Ultimately an algorithm that integrates clinical dosing criteria and pharmacogenetics data was established and tested.^[7] The pharmacogenetically enhanced algorithm performed better than the clinical algorithm in selecting the therapeutic dose.^[7]
Few studies exist that evaluate the knowledge of pharmacists related to pharmacogenetics. In one study by Kadafour et al., healthcare professionals providing anticoagulation services were surveyed regarding warfarin pharmacogenetic testing. The majority of respondents were pharmacists (63.9%) providing anticoagulation services for more than 5 years (62.2%). However, over 80% (80.1%) did not have pharmacogenetic testing available at their practice site. From the five questions assessing knowledge of pharmacogenetic testing associated with warfarin anticoagulation, on average respondents scored 2 out of 5. Respondents with testing available at their practice site scored significantly higher with a score of 3 out of 5 (p = 0.03 by Wilcoxon-rank sum test).^[8]
In terms of attitudes regarding pharmacogenetics among pharmacists and other healthcare professionals, our current understanding is very limited. This is unfortunate given that there are likely to be ethical, legal and social implications of the routine use of pharmacogenetics. These include concerns regarding privacy, confidentiality, informed consent, cost, equity of access to treatments that may be more expensive, genetic testing in minors, duty to warn of potential risk for adverse drug reactions, and inappropriate marketing of race-based medications.^[9,10] Moreover, the implementation of pharmacogenetics in clinical practice is highly dependent upon acceptance of pharmacogenetics among pharmacists and other healthcare professionals.
One of the few existing studies concerning attitudes about pharmacogenetics is a study by Rogausch and colleagues.^[11] Findings from this study suggest that attitudes and concerns regarding pharmacogenetics often differ between patients and physicians. They found that while patients were primarily concerned with privacy issues and adverse treatment by employers or insurance companies, physicians were concerned that employers or insurance companies might pressure patients into pharmacogenetic testing and patients might be disadvantaged if test results indicated a need for higher doses of a drug. In the study by Kadafour and colleagues, over 35% of the participants agreed that warfarin pharmacogenetic testing will help to more accurately determine initial warfarin dose, 32% agreed that warfarin pharmacogenetic testing will help achieve therapeutic international normalized ratio more quickly and 26% agreed that warfarin pharmacogenetic testing will decrease the incidence of bleeding adverse events.^[8] An increasing number of drugs have a response that is linked to genetic differences in drug metabolizing enzymes, drug transporters or drug targets. Pharmacists are positioned in communities and in health systems where they may be presented with a patient prescribed a medication that requires at least an understanding of pharmacogenetic principles to address the relationships between genetics and metabolizing enzymes, transporters or drug targets.
Certainly, the call to action by the International Society of Pharmacogenomics that was reported in a paper by Gurwitz et al. in 2005 highlighted the need for pharmacogenomics education for medical, pharmaceutical and other health professionals schools.^[12] From the studies on pharmacy education, Latif et al. found that 78% of 41 schools provided pharmacogenomics education, however, only 39% of the doctor of pharmacy programs included this education.^[13] By 2010, Murphy et al. found that 92% of schools provided educational content on pharmacogenomics, with 89% providing content within the clinical degree program or doctor of pharmacy program.^[14]
The purpose of this article is to share select findings from a larger study concerning knowledge and attitudes regarding pharmacogenetic testing among healthcare professionals. For this article, the focus is limited to the responses of pharmacists from North Carolina, USA.

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