It has been reported that the increase in human immunodeficiency virus (HIV) sequence diversity in drug resistance surveillance specimens may be used to classify the duration of HIV infection as 1 year. We describe a mixed base classifier (MBC) optimized to categorize the duration of subtype B infections as 6 months on the basis of sequences for drug resistance surveillance specimens and compared MBC findings with those of serologic methods.
The behavior of the MBC was examined across a range of thresholds for calling mixed bases. MBC performance was then evaluated using either complete pol sequences or sites reflecting evolutionary pressures (HLA selection sites, sites that increased in entropy over the course of infection, and codon positions).
The MBC performance was optimal when secondary peaks on the sequencing chromatogram accounted for at least 15% of the area of primary peaks. A cutoff of