If the sample grows more than normal, it is resistant to the medication. It can take over a month to get the results. However, new phenotypic tests are quicker. The genetic code of the sample virus is compared to the wild type. The code is a long chain of molecules called nucleotides.
Results come back in about two weeks.
This new type of resistance test combines some elements of genotypic and phenotypic testing. First, genotypic testing is done on the sample. Then other virus samples with the same genetic code are identified. The test tells you how the sample virus is likely to behave based on the matched samples. The virtual phenotype is faster and less expensive than a phenotypic test.