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Test Code HIQDR HIV-1 RNA Quantification with Reflex to Genotypic Drug Resistance to Reverse Transcriptase, Protease, and Integrase Inhibitors, Plasma


Ordering Guidance


This test is intended for quantification of HIV-1 RNA level in plasma specimens of individuals with known HIV-1 infection and for identification of drug resistance-associated HIV-1 genotypic mutations prior to or while receiving combination antiretroviral therapy.

 

Prior to requesting this test, the patient must have a known HIV-1 infection. The following tests are available to screen and confirm the HIV-1 infection status:

-HVCOP / HIV-1 and HIV-2 Antigen and Antibody Routine Screen, Plasma

-HIVDX / HIV-1 and HIV-2 Antigen and Antibody Diagnostic Evaluation, Plasma

 

If only HIV-1 genotypic mutation testing is needed, order HIVDR / HIV-1 Genotypic Drug Resistance to Reverse Transcriptase, Protease, and Integrase Inhibitors, Plasma.



Shipping Instructions


1. Ship specimen frozen on dry ice.

2. If shipment will be delayed for greater than 24 hours, freeze plasma specimen at -20 to -80° C until shipment on dry ice.



Specimen Required


Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube: Lavender top (EDTA)

Submission Container/Tube: Plastic vial

Specimen Volume: 3.6 mL

Collection Instructions:

1. Centrifuge blood collection tube and aliquot plasma into plastic vial per collection tube manufacturer's instructions (eg, centrifuge and aliquot within 2 hours of collection for BD Vacutainer tubes).

2. Freeze aliquoted plasma for shipment.


Secondary ID

616917

Useful For

Quantifying plasma HIV-1 RNA levels (viral load) in individuals (including children) with known HIV-1 infection, followed by identification of HIV-1 genotypic mutations associated with resistance to nucleotide and non-nucleoside reverse-transcriptase inhibitors protease inhibitors , and integrase strain transfer inhibitors

 

Guiding initiation or change of combination antiretroviral therapy in individuals, including children, with HIV-1 infection

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
HIVDR HIV-1 Genotypic Drug Resistance, P Yes No

Method Name

Real-Time Reverse Transcription-Polymerase Chain Reaction (RT-PCR)

Reporting Name

HIV-1 RNA Quant Reflex to Resist, P

Specimen Type

Plasma EDTA

Specimen Minimum Volume

2 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma EDTA Frozen (preferred) 55 days
  Refrigerated  5 days

Reject Due To

Gross hemolysis Reject
Gross lipemia OK

Clinical Information

HIV-1 is an RNA virus that infects human host cells and is then converted to complementary DNA by the action of viral reverse transcriptase. HIV-1 is the causative agent of AIDS, a severe, life-threatening condition, and the virus has been isolated from asymptomatic, infected individuals at high-risk for AIDS. Accounting for over 99% of HIV infections in the world, HIV-1 is transmitted by sexual contact, by exposure to infected blood or blood products, from an infected pregnant woman to fetus in utero or during birth, or from an infected mother to infant via breast feeding.

 

Multiple clinical studies of plasma HIV-1 viral load (expressed as HIV-1 RNA copies/mL of plasma) have shown a clear relationship of HIV-1 RNA copy number to stage of HIV-1 disease and efficacy of anti-HIV-1 therapy. Quantitative HIV-1 RNA level in plasma (ie, HIV-1 viral load) is an important surrogate marker in assessing the risk of disease progression and monitoring response to anti-HIV-1 drug therapy in the routine medical care of HIV-1-infected patients.

 

Studies have identified a number of mutations associated with antiviral resistance. Genotypic analysis allows identification of nucleotide changes associated with HIV drug resistance. When combination therapy fails, genotyping for drug resistance mutations may help direct appropriate changes in antiretroviral therapy and may result in at least a short-term benefit, as evidenced by viral load reduction.

Reference Values

Undetected

Interpretation

HIV-1 RNA Quantification:

This assay has a HIV-1 RNA quantification result range of 20 to 10,000,000 copies/mL (1.30-7.00 log copies/mL) in plasma.

 

An "Undetected" result indicates that the assay was unable to detect HIV-1 RNA within the plasma specimen.

 

A result of "<20 copies/mL" indicates that HIV-1 RNA is detected, but the level present is less than the lower quantification limit of this assay. Due to the increased sensitivity of this assay, patients with previously low or undetectable HIV-1 viral load may show increased or detectable viral load with this assay. However, the clinical implications of a viral load below 20 copies/mL remain unclear. Possible causes of such a result include very low plasma HIV-1 viral load present (eg, in the range of 1-19 copies/mL), very early HIV-1 infection (ie, <3 weeks from time of infection), or absence of HIV-1 infection (ie, false-positive result).

 

A result of ">10,000,000" with the result comment of "HIV-1 RNA level is >10,000,000 copies/mL (>7.00 log copies/mL). This assay cannot accurately quantify HIV-1 RNA above this level" indicates that HIV-1 RNA is detected, but the level present is above the upper quantification limit of this assay.

 

For the purpose of monitoring patient's response to antiretroviral therapy, the US Health and Human Services Panel on Antiretroviral Guidelines for Adults and Adolescents defines virologic failure as a confirmed viral load of greater than 200 copies/mL, which eliminates most cases of viremia resulting from isolated blips or assay variability. Confirmed viral load rebound (ie, >200 copies/mL) on 2 separate tests obtained at least 2 to 4 weeks apart should prompt a careful evaluation of patient's tolerance of current drug therapy, drug-to-drug interactions, and patient adherence.

 

If the viral load is greater than or equal to 1000 copies/mL, genotypic antiviral drug resistance mutation analysis is performed automatically at an additional charge.

 

Genotypic Drug Resistance:

Codon sequences of the reverse transcriptase, protease and integrase coding region of the HIV-1 genome are compared with those in the Stanford HIV database of known antiretroviral resistance-associated mutations determined with the assay software application. Results are provided on the interpretation of those codon changes associated with resistance to individual antiretroviral drugs.

 

Susceptible (SUSC) indicates that the codon mutations present in patient's HIV-1 strain have not been associated with resistance to the specific drug (Stanford HIVdb total score 0 to 9).

 

Potential Low-Level Resistance (PLR) indicates that codon mutations detected have been associated with possible reduction in susceptibility to the specific drug (Stanford HIVdb score 10 to 14).

 

Low-Level Resistance (LR) indicates that codon mutations detected have been associated with reduction in susceptibility to the specific drug (Stanford HIVdb score 15 to 29).

 

Intermediate Resistance (IR) indicates that codon mutations detected have been associated with reduction in susceptibility to the specific drug (Stanford HIVdb score 30 to 59).

 

High-level Resistant (HR) indicates that codon mutations detected have been associated with maximum reduction in susceptibility to the specific drug (Stanford HIVdb ≥60).

 

Unable to genotype indicates that the sequence data obtained are of poor quality to determine the presence or absence of resistance-associated codon mutations in the patient's HIV-1 strain. Probable causes of such poor sequence data include polymorphism in the region of the sequencing primers interfering with primer binding and subsequent sequencing reaction, or low viral load (ie, <1000 copies/mL).

 

Inconclusive indicates inability of the assay to reliably determine antiviral resistance because of the presence of polymerase chain reaction inhibitors or ambiguous or incomplete viral target sequences generated from the assay.

CPT Code Information

87536

0219U (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
HIQDR HIV-1 RNA Quant Reflex to Resist, P 70241-5

 

Result ID Test Result Name Result LOINC Value
616917 HIV-1 RNA Detect/Quant, P 70241-5

Forms

If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.