Interpretation

Detectable HIV-1 genotypic mutations conferring resistance to an antiviral drug are reported as amino acid codon changes (eg, M184V) resulting from the nucleic acid base alterations, according to the interpretative algorithm of the Stanford HIV Database program. The codon mutations are categorized and interpreted in relation to previously published data of phenotypic antiviral susceptibility tests on virus that harbor such mutations. Each codon mutation is assigned a drug penalty score. The total score generated from all mutations relevant to the specific antiviral drug is used to estimate the level of resistance to that drug. These interpretive rules may be updated periodically by the Stanford HIV Database Team after reviewing newly published data on HIV-1 genotypic drug resistance-associated codon mutations.

Susceptible (SUSC) indicates that the codon mutations present in patient's HIV-1 strain have not been associated with resistance to the specific drug (Stanford HIVdb total score 0 to 9).

Potential Low-Level Resistance (PLR) indicates that codon mutations detected have been associated with possible reduction in susceptibility to the specific drug (Stanford HIVdb score 10 to 14).

Low-Level Resistance (LR) indicates that codon mutations detected have been associated with reduction in susceptibility to the specific drug (Stanford HIVdb score 15 to 29).

Intermediate Resistance (IR) indicates that codon mutations detected have been associated with reduction in susceptibility to the specific drug (Stanford HIVdb score 30 to 59).

High-level Resistant (HR) indicates that codon mutations detected have been associated with maximum reduction in susceptibility to the specific drug (Stanford HIVdb ≥ 60).

Unable to genotype indicates that the sequence data obtained are of poor quality to determine the presence or absence of resistance-associated codon mutations in the patient's HIV-1 strain. Probable causes of such poor sequence data include polymorphism in the region of the sequencing primers interfering with primer binding and subsequent sequencing reaction, or low viral load (ie, <1000 copies/mL).

Inconclusive indicates inability of the assay to reliably determine antiviral resistance because of the presence of polymerase chain reaction inhibitors or ambiguous or incomplete viral target sequences generated from the assay.