Misinterpretation of direct-to-consumer (DTC) genetic testing results could pose a clinical risk to individuals, according to a case study published in Clinical Pharmacology & Therapeutics. In the reported case, rare genotypes for the gene encoding thiopurine methyltransferase (TPMT) were misinterpreted by a DTC company and could have affected dosing treatment decisions. The authors say that professional interpretation and test validation, comparable to a CLIA-certified lab, are necessary to ensure that DTC test results are not misapplied. “We are not advocating the end of DTC testing, nor are we universally denouncing DTC genetic testing companies,” the authors write. “However, we feel that the interpretations must be accurate and reasonable, with adequate and freely available interpretation support for consumers and physicians.” A male patient received a DTC genetic test (company unnamed) based on the standard HumanHap550 panel (Illumina) supplemented with a custom set of 25,000 additional single nucleotide polymorphisms selected by the company. His results report that for TPMT he has “one *3B mutation and one *3C mutation, a homozygous nonfunctional alleles pattern resulting in significant enzyme deficiency. A person with these mutations has an increased risk of toxicity when treated with thiopurine drugs at standard doses.” The report did contain the […]