They will usually tell you what this means in terms of drug resistance. Tables 1 and 2 show the known muta-tions that give resistance to current HIV drugs. The genotypic test report can be hard to understand. You and your doctor may need to consult a specialist who knows how to read and interpret the results. The Pros and Cons Table 3 lists advantages and disadvantages of genotypic tests.
Results usually return within a week.
A major problem with genotypic testing is that it will miss unknown gene mutations. Also, while the effects of some mutations are clear-cut, this is not always true. A mutation that does not cause resistance by itself could lead to resistance when combined with other mutations. Also, resistance to one drug sometimes results in increased sensitivity to another. The most common way that genotypic testing is done uses a machine that reads the gene sequence of the protease and RT genes.