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Case 2: Features of Genotypic and Phenotypic Resistance Assays

You answered:

D When a patient is undergoing a change in antiretroviral therapy because of virologic failure, genotypic resistance testing does not provide any benefit in improving virologic responses.

This answer is incorrect. Several clinical trials have demonstrated that genotypic resistance testing improves virologic response among patients undergoing salvage antiretroviral therapy, primarily among patients that have experienced virologic failure to a single or a few regimens. Fewer trials have been conducted regarding phenotypic testing, and the results to date have been equivocal. Attention to the patient's antiretroviral history and the experience of the clinician in using resistance data have also been found to impact on the suppressive effect of the prescribed salvage regimen.

Choose another answer:

A Compared with the phenotypic assay, the genotypic assay is more expensive and has a longer turnaround time.
B The M184V mutation notation refers to the replacement of the amino acid methionine (M) by valine (V) at amino acid position 184.
C The genotypic assay detects resistance in greater than 98% of minority populations of HIV that exist within an individual.

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