Susceptibility Test Methods: Viruses

Abstract Testing for viral susceptibility, primarily via genotypic drug resistance mutation testing, is now standard practice for the management of viral infections for optimum patient care. Antiviral resistance is expressed as a drop in the efficacy of a drug to inhibit viral replication. The virus being treated is inherently resistant to the drug(s) being given. Alternatively, host biological and socio‐behavioral factors or inadequate dosing may influence therapeutic success. Host physiologic factors can interfere with a successful clinical response. Viral susceptibility testing can identify resistance and guide patient management strategies. The clinical category and status of the patient are important in determining whether antiviral resistance testing is indicated. Genotypic viral susceptibility testing requires knowledge of the mutations that confer antiviral resistance. FDA‐cleared genotypic antiviral resistance tests include software to analyze the raw sequence and render a resistance interpretation. The pharmaceutical industry is actively investigating and developing new antiviral drugs.