• Guide selection of antiretroviral drugs

• Predict HIV-1 resistance to the integrase inhibitor raltegravir (Isentress^®′)

• Monitor transmission of raltegravir-resistant HIV-1

Despite continuing advances in treatment for HIV-1 infection, antiretroviral therapy (ART) may fail due to the accumulation of drug resistance mutations. Identifying such mutations can optimize and guide selection of antiretroviral drugs. Thus, detection of mutations associated with treatment resistance is recommended at entry into care, when ART is initiated or changed, when treatment failure is suspected, or when otherwise clinically indicated.^1,2 When virologic failure is suspected, resistance testing should be performed while the patient is taking the drug or within 4 weeks after discontinuing it.¹

This HIV-1 Integrase Genotype test is designed to detect mutations associated with resistance to raltegravir, the first FDA-approved HIV integrase inhibitor. Raltegravir represents a new antiretroviral class in which the catalytic activity of integrase is inhibited, thereby preventing formation of the HIV provirus required for viral propagation. The major mutations associated with raltegravir resistance include N155H, Q148H/K/R, and Y143C/H/R.^3,4 In addition, minor mutations that may contribute to resistance are detected and reported.

• HIV-1–infected individuals receiving raltegravir and showing evidence of virologic failure

• HIV-1–infected individuals for whom raltegravir treatment is being considered

2 mL frozen EDTA plasma (lavender-top tube); 0.6 mL minimum.

Alternatively, submit PPT-potassium EDTA plasma (white-top tube).

Centrifuge blood within 6 hours of collection; transfer the plasma to a separate plastic screw-cap vial and freeze. Provide the most recent viral load data: collection date and level.

• Reverse transcription and PCR amplification of the HIV-1 integrase gene

• DNA sequencing of the entire integrase gene (codons 1–288)

• Report includes detected mutations and predicted drug resistance to raltegravir

• Analytical sensitivity: 1000 copies/mL

• Analytical specificity: detects mutations in the integrase gene of HIV-1 group M subtype B and various non-B subtypes

• Aliases: Isentress (raltegravir, MK-0518) resistance, HIV-1 integrase mutations

• CPT codes*:  87901

Lack of mutations associated with raltegravir resistance suggests the patient may be eligible for treatment with raltegravir.⁴ On the other hand, mutations predictive of raltegravir resistance are associated with drug failure, and alternative therapy should be considered.³

Therapeutic failure may be due to factors other than resistance, including poor adherence to the drug regimen, suboptimal therapy or drug bioavailability, and immunologic decline. Thus, in clinical practice, physicians select therapeutic regimens on the basis of the patient’s antiretroviral treatment history, viral load, clinical status, and potential metabolic toxicity as well as resistance information.