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HIV-1 Resistance Genotyping by Reverse Transcriptase Phenotypic Assay

Published: August 9, 2026Updated: August 16, 2026

This test measures how HIV-1 drugs affect the virus’s ability to multiply in your blood. It helps doctors choose the best treatment by identifying drug resistance patterns.

Quick summary

["Determines which HIV drugs may work best by checking how resistant the virus is to common treatments."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
83327-7
Short code
HIV 1 RNA phenotype Islt
Synonyms
HIV 1 RNA phenotype Islt
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
phenotyping
CPT
86701
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What This Test Measures

The test analyzes the HIV-1 reverse transcriptase enzyme, which is critical for the virus’s replication. By assessing how resistant this enzyme is to specific antiretroviral drugs, it provides data on potential treatment effectiveness.

Why It’s Done

Doctors may order this test if you’re starting HIV treatment, experiencing treatment failure, or developing resistance to certain drugs. It helps tailor therapy to avoid drug-resistant strains.

Sample Collection and Preparation

A blood sample is taken, typically from a vein. The sample is processed to isolate viral RNA, which is then used to grow the virus in the lab. This allows for testing how resistant the virus is to common antiretroviral drugs.

How Results Are Used

Results show the virus’s sensitivity or resistance to specific drugs, helping doctors adjust your treatment plan. This may include switching drugs, adding new ones, or adjusting dosages to improve effectiveness and reduce side effects.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

HIV Resistance Phenotyping (RT)

Frequently asked questions

What does a positive or negative result mean?
A positive result indicates that the virus has developed resistance to certain drugs, meaning those medications may not work as expected. A negative or low resistance result suggests the virus is more likely to respond to those drugs.
How long does it take to get results?
Results typically take about 2 to 4 weeks from the time the sample is collected, as this involves viral culture and drug susceptibility testing in a specialized lab.
Can this test be done on other types of samples?
No, this test specifically requires a blood sample to isolate viral RNA for analysis. Other tests may be used for initial HIV detection or monitoring.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy