3
Drug Resistance Testing
Î Initial drug resistance testing is recommended for all persons with
HIV infection (AIII). If therapy is deferred, repeat testing at the time of
ART initiation should be considered (CIII).
Î A genotypic assay is generally preferred for ARV-naive persons (AIII).
If transmitted integrase strand transfer inhibitor (INSTI) resistance
is a concern, providers may wish to supplement standard genotypic
resistance testing with genotypic testing for resistance to this class of
drugs (CIII).
Î Perform drug resistance testing to select active drugs when changing
ARV regimens in cases of virologic failure and HIV RNA levels >1,000
copies/mL (AII). Consider testing in persons with >500 but <1,000
copies/mL (BII).
Î Genotypic testing is the preferred resistance testing to guide therapy
in patients with suboptimal virologic responses or virologic failure
while on first or second regimens (AIII).
Î Addition of phenotypic testing to genotypic testing is generally
preferred for persons with known or suspected complex drug
resistance mutation patterns, particularly to protease inhibitors (BIII).
Î Perform drug resistance testing in the setting of virologic failure while
the patient is taking ARV drugs, or within 4 weeks after discontinuing
therapy (AII).
Î Perform genotypic resistance testing for all pregnant women prior
to initiation of therapy (AIII) and for those entering pregnancy with
detectable HIV RNA levels while on therapy (AII).
Î In persons failing INSTI-based regimens, perform genotypic testing
for INSTI resistance to determine whether to include a drug from this
class in subsequent regimens (AII).
HLA-B*5701 Screening
Î Screen for HLA-B*5701 before starting patients on an abacavir-
containing regimen, to reduce the risk of hypersensitivity reaction (AI).
Î HLA-B*5701-positive patients should NOT be prescribed abacavir (AI).
The positive status should be recorded as an abacavir allergy in the
patient's medical record (AII).
Î When HLA-B*5701 screening is not readily available, initiate abacavir
with appropriate clinical counseling and monitoring for any signs of
hypersensitivity reaction (CIII).
Coreceptor Tropism Assays
Î Perform coreceptor tropism assay whenever the use of a CCR5
inhibitor is being considered (AI).
ÎA genotypic tropism assay can be used as an alternative to a phenotypic
tropism assay before initiation of a CCR5 antagonist-containing regimen (BII).
Î Consider coreceptor tropism testing for patients who exhibit virologic
failure on a CCR5 inhibitor (CIII).
