The HIV-1 genotype test is performed by (1) reverse transcription, (2) amplification of the HIV-1 reverse transcriptase (codons 1-320) and protease (codons 1-99) genes by polymerase chain reaction (PCR), and (3) Sanger DNA sequencing.
Test Codes: 34471, 34949, 91691, 91692
HIV-1 drug resistance testing is recommended for people with HIV at entry into care to guide initial antiretroviral (ARV) regimen selection.1,2 Resistance testing is also recommended for pregnant people with HIV before initiation of therapy and for those entering pregnancy with detectable HIV RNA levels.1 Resistance testing is also recommended for patients with treatment failure.
Testing in the context of virologic failure should be performed while the person is still taking their ARV regimen, or, if that is not possible, within 4 weeks after discontinuing their regimen.1,2
If transmitted integrase strand transfer inhibitor (INSTI) resistance is suspected, if the person has ever used long-acting cabotegravir (CAB-LA) as pre-exposure prophylaxis, or if the person has ever received an INSTI-based regimen for post-exposure prophylaxis, providers should ensure that genotypic resistance testing also includes the integrase gene.1 Please refer to HIV-1 Integrase Genotype | Quest Diagnostics for further information on our integrase genotype test.
Genotypic assays detect drug resistance mutations in relevant viral genes and use various tools to interpret resistance test results.1 Phenotypic assays measure the ability of a virus to grow in the presence of different concentrations of ARV drugs.1
Genotypic testing is preferred over phenotypic testing for patients with virologic failure on first- or second-line regimens and in people for whom resistance mutation patterns are not expected to be complex.
Phenotypic testing in addition to genotypic testing is recommended for people with known or suspected complex drug resistance mutation patterns.1
Mutations listed in the 2022 edition (or newer) of the International Antiviral Society-USA (IAS-USA) drug resistance mutations list are reported. These include resistance-associated mutations for nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), and protease inhibitors (PIs).3
- Nucleoside reverse transcriptase inhibitors (NRTIs):
- Abacavir
- Didanosine
- Emtrcitabine
- Lamivudine
- Stavudine
- Tenofovir
- Zidovudine
- Non-nucleoside reverse transcriptase inhibitors (NNRTIs):
- Doravirine
- Efavirenz
- Etravirine
- Nevirapine
- Rilpivirine
- Protease inhibitors (PIs):
- Atazanavir
- Darunavir
- Fosamprenavir
- Indinavir
- Lopinavir
- Saquinavir
- Tipranavir
Quest Diagnostics utilizes an in-house–developed, rules-based system that takes into account published scientific literature that correlates genotype to phenotype or genotype to clinical outcome. The Quest algorithm is also informed by the Stanford HIV Drug Resistance Database (HIVdb) interpretation system.4 The algorithm is periodically reviewed and updated as warranted.
As this test uses viral RNA extracted from the plasma of HIV--infected patients, a minimum viral load of 500 to 1,000 copies/mL is recommended. If the patient’s viral load is undetectable or too low for a plasma RNA genotype, a proviral DNA genotype test may be considered (HIV-1 Resistance Proviral DNA RTI PI Integrase Inhibitors | Quest Diagnostics).
A result of “not detected” indicates that Quest was unable to amplify any HIV-1 viral RNA for genotyping. Common reasons for this may include insufficient viral load (see Question 7), viral mutations that inhibited the reverse transcription or PCR amplification, or specimen collection or transportation issues that may have resulted in degradation of the HIV-1 viral RNA.
Please see the test ordering instructions for guidelines to properly collect, store, and transport specimens for HIV-1 genotyping.
Yes. For test details, please see the FAQ for HIV integrase genotyping (HIV-1 Integrase Genotype | Quest Diagnostics) and order HIV-1 Genotype (RTI, PI, Integrase Inhibitors) (test code 91692) or HIV-1 RNA, Quantitative, Real-Time PCR with Reflex to Genotype (RTI, PI, Integrase) (test code 91691). The integrase genotype may also be ordered as a standalone test: HIV-1 Integrase Genotype (test code 16868).
References
- Panel on Antiretroviral Guidelines for Adults and Adolescents. Guidelines for the use of antiretroviral agents in adults and adolescents with HIV. Department of Health and Human Services. Accessed 10/08/2024. Available at https://clinicalinfo.hiv.gov/en/guidelines/adult-and-adolescent-arv
- Gandhi RT, Bedimo R, Hoy JF, et al. Antiretroviral drugs for treatment and prevention of HIV infection in adults: 2022 recommendations of the International Antiviral Society-USA Panel. JAMA. 2023;329(1):63-84. doi: 10.1001/jama.2022.22246
- Wensing AM, Calvez V, Ceccherini-Silberstein F, et al. 2022 update of the drug resistance mutations in HIV-1. Topics in Antiviral Medicine. 2022;30(4):559-574
- HIV Drug Resistance database. https://hivdb.stanford.edu/
This FAQ is provided for informational purposes only and is not intended as medical advice. A physician’s test selection and interpretation, diagnosis, and patient management decisions should be based on the physician’s education, clinical expertise, and assessment of the patient.
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