Laboratory guidelines for the practical use of HIV drug resistance tests in patient follow-up

HIV drug resistance is one of the major limitations in the successful treat ment of HIV-infected patients using currently available antiretroviral comb ination therapies. When appropriate, drug susceptibility profiles should be taken into consideration in the choice of a specific combination therapy. Guidelines recommending resistance testing in certain circumstances have be en issued. Many clinicians have access to resistance testing and will incre asingly use these results in their treatment decisions. In this document, w e comment on the different methods available, and the relevant issues relat ing to the clinical application of these tests. Specifically, the following recommendations can be made: (i) genotypic and phenotypic HIV-1 drug resis tance analyses can yield complementary information for the clinician. Howev er, insufficient information currently exists as to which approach is prefe rable in any particular clinical setting; (ii) when HIV-1 drug resistance t esting is required, it is recommended that testing be performed on plasma s amples obtained before starting, stopping or changing therapy, on samples t hat have a viral load above the detection limit of the resistance test; (ii i) the panel recommends that genotypic and phenotypic HIV-1 drug resistance testing for clinical purposes be performed in a certified laboratory under strict quality control and quality assurance standards; and (iv) the panel recommends that resistance testing laboratories provide clinicians with re sistance reports that include a list of drug-related resistance mutations ( genotype) and/or a list of drug-related fold resistance values (phenotype), with interpretations of each by an experienced virologist. The interpretat ion of genotypic and phenotypic analysis is a complex and developing scienc e, and in order to understand HIV-1 drug resistance reports, communication between the requesting clinician and the expert that interpreted the resist ance report is recommended.