Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1385 page)

HUMAN IMMUNODEFICIENCY VIRUS TYPE 1 (HIV-1) GENOTYPE (MOLECULAR ASSAY)*

   Definition

   HIV-1 genotyping detects HIV genomic mutations that confer resistance to specific types of antiretroviral drugs. Current sequence-based assays detect resistance mutations in the protease (PR) and part of the reverse transcriptase (RT) genes. Two Food and Drug Administration (FDA)-approved genotyping methods are commercially available: the ViroSeq HIV-1 genotyping system, version 2.0 (Celera Diagnostics) and the Trugene HIV-1 genotyping system for drug resistance (Siemens Healthcare Diagnostics).

   Use

   As an aid in monitoring and treating HIV-1–infected individuals:

   At initial presentation, before initial drug therapy

   At drug therapy failure

   Limitations

   Viral load not <1,000 copies/mL for TrueGene and 2,000 copies/mL for ViroSeq.

   The FDA-approved tests are specific for analysis of subtype B HIV-1 only. For analysis of non–B HIV-1 strains that represent up to 90% of HIV-1 variants circulating worldwide, lab-developed tests should be used.

HUMAN IMMUNODEFICIENCY VIRUS TYPE 1 (HIV-1) RNA, QUANTITATIVE VIRAL LOAD (MOLECULAR ASSAY)
*

   Definition

   The HIV-1 viral load assay quantifies HIV-1 RNA in the plasma of HIV-1 infected individuals. Result of HIV-1 RNA testing are reported in copies/mL and/or International Units/mL (IU/mL). Results reported in IU/mL can be compared between laboratories independently which platform was used to obtained results.

   
Normal range:
Not detected when the result is below the level of detection of the assay.

   Use