Frequently Asked Questions

Castle Biosciences operates clinical laboratories in Phoenix and Pittsburgh. The Company’s laboratories are College of American Pathologists (CAP) accredited and Clinical Laboratory Improvement Amendments (CLIA) certified, reflecting the Company’s commitment to high-quality standards and excellence in patient care. Castle's laboratories are licensed to perform tests throughout the United States.

Many psychiatric drugs are metabolized by the CYP enzymes, including 2D6, 2C19 and 2C9, which are genes included in our IDgenetix® tests. The CYP2D6 enzyme, for example, primarily or substantially metabolizes a number of selective serotonin reuptake inhibitors, or SSRI, serotonin-norepinephrine reuptake inhibitors, or SNRI, and tricyclic antidepressants or TCA, which are, according to IMS Health, the three most-commonly prescribed drug classes in psychiatry, as well as antipsychotic drugs. Our neuropsychiatric tests also include variant analysis for informative receptor and transporter genes associated with clinical response to psychiatric drugs and risk of side effects, such as SLC6A4 and HTR2A, which are important factors for psychiatric drugs. More than 10% of patients taking antidepressants experience significant adverse drug reactions. Twenty-four psychiatry drugs are included on the FDA’s Table of Pharmacogenomic Biomarkers in Drug Labeling as having PGx information in the drug labeling. For additional Information: Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines for CYP2D6 and CYP2C19 genotypes and dosing of tricyclic antidepressants.

Link to Publication

FDA Table of Pharmacogenetic Biomarkers in Drug Labeling

References: 1) Ingelman-Sundberg M, Sim S, Gomez A, Rodriguez-Antona C. Influence of cytochrome P450 polymorphisms on drug therapies: Pharmacogenetic, pharmacoepigenetic and clinical aspects. Pharmacology & Therapeutics. 2007;116: 496–526. 2) Ingelman-Sundberg M, Rodriguez-Antona C. Pharmacogenetics of drug-metabolizing enzymes: implications for a safer and more effective drug therapy. Philos Trans R Soc Lond B Biol Sci. 2005;360:1563-1570. 3) Fanikos J, Grasso-Correnti N, Shah R, Kucher N, Goldhaber SZ. Major bleeding complications in a specialized anticoagulation service. Am J Cardiol. 2005;Aug 15;96(4):595-598. 4) Machado M, Iskedjian M, Ruiz I, Einarson TR. Remission, dropouts, and adverse drug reaction rates in major depressive disorder: a meta-analysis of head-to-head trials. Curr Med Res Opin. 2006;Sept. 22(9), 1825-1837.

We have our own educational channel on YouTube called IDgenetix® TV with tons of relevant educational Pharmacogenomics (PGx) pearls that you can listen on at own time. Our MSL who is an expert in PGx can speak with you on an individual basis regarding any questions you may have or review your patient’s IDgenetix report with you. For ease and efficiency, please use the Calendly link to set up a personalized session with our MSL, Behnaz Sarrami, MS, PharmD.

Based on the largest depression study conducted, funded at 35 million US dollars, the STAR*D Trial showed that about half the patients do not respond on the first round of treatment for depression. Using IDgenetix® as a tool to help guide therapy rather than the traditional trial-and-error mental health prescribing is key in getting patients mentally stable sooner.

Depression and Anxiety Individual patient response to medications is influenced by genetic variation in the enzymes responsible for drug metabolism as well as targeted receptors and transporters. The family of cytochrome P450 genes code for enzymes responsible for approximately 80% of phase 1 drug metabolism. Genetic variation of these genes alone is estimated to influence 20-25% of all drug therapies to the extent that outcome is affected. [1] Why is this important? Variations in metabolism can cause life-threatening toxicity in one patient and reduce drug effectiveness in another.[2] Clinically significant genetic alterations in the cytochrome P450 (CYP) genes can result in decreased or increased enzyme activity. These alterations in enzyme function are categorized into four phenotypes. Knowing a patient’s metabolic phenotype and its impact on drug metabolism can empower clinical treatment decisions, increase drug efficacy, and reduce the risk of adverse events. Extensive Metabolizers (EM) carry 2 functional genes and have normal enzyme activity. Standard medication dosing is appropriate for extensive metabolizers. Poor Metabolizers (PM) have severely reduced or no functional capacity to metabolize substrate medications. Poor metabolizers are at risk for side effects due to toxic drug accumulation and may require lower doses. Intermediate Metabolizers (IM) also have a severely reduced capacity to metabolize drugs and therefore may also require modified drug doses. In contrast, Ultra-Rapid Metabolizers (UM) typically carry multiple copies of the same gene and have elevated enzyme activity and may need increased drug dosing or decreased drug dosing, in the case of pro-drugs, in order to offset the higher rate of metabolism.

Based on our pharmaco-economical RCT, the direct and indirect cost of depression is about $30,000 annually per patient. Indirect costs such as loss of job and suicide takes a huge toll on not just the patients but the patient’s families and the healthcare system. IDgenetix® has shown to save each patient about $6,000 per year by personalizing patient’s medications based on their genetic makeup.

Each person has two alleles that are inherited from each parent. Alleles are variations of a gene that determine our phenotype.

Below is the summary of the AltheaDx randomized controlled trial that showed using IDgenetix® improved patient’s clinical outcomes with statistical significance.

The IDgenetix® Advantage The IDgenetix® Testing Process Consists of Three Important Steps Obtaining therapeutic benefit from a medication is dependent on the functioning of metabolic enzymes and key transporter and receptor proteins at the biological site of action. Each IDgenetix test analyzes genes and gene mutations with a demonstrated role in influencing medication response, including efficacy or adverse events. IDgenetix testing provides tailored treatment recommendations for each patient by utilizing our bioinformatic algorithm to integrate patient specific health information with comprehensive genetic results.

Please call our customer service staff at 866-788-9007 or email.