Understanding the statistical analysis of resistance data

Excerpt

Phenotypic resistance data are a continuous statistical variable that indicate the concentration of drug needed to inhibit the replication of a patient's virus. Typically, this is measured by specifying the concentration of drug needed to inhibit 50% or 90% of virus replication (IC₅₀ or IC₉₀, respectively), or by comparing the fold change in drug concentration required to inhibit the replication of the patient's virus compared with a sensitive virus isolate. In contrast, genotypic resistance data are typically a series of binary variables documenting the presence of specific mutations in the amino acid sequences of the HIV-1 genome in the reverse transcriptase (RT) or protease (PR) regions (e.g. yes/no variables for resistance mutations 41L, 65R, 67N and 184V). This chapter focuses on the statistical analysis of the genotypic resistance data that are generated from routine clinical care.