HIV-1 Tropism testing
An important subclass of drugs used in patients with HIV-1 infection have been designed to inhibit HIV-1 viral entry. These entry inhibitors are drugs which target one of the receptors that can be used (in addition to the main receptor CD4 by HIV-1), as a coreceptor to enter the cell.
The most important HIV coreceptors are the chemokine receptors CCR5 and CXCR4. HIV-1 particles fall into three classes according to which of them they can use to enter a cell: some can only use CCR5, others can only use CXCR4, and some can use either of them. Before and during drug treatment with a coreceptor antagonist, it is important to find out about the coreceptor usage of the virus population in the patient.
The amino acid sequence of the V3 loop can be determined by RT-PCR of isolated RNA extracted from plasma samples and analysed using the Trugene software. The sequence can be inserted into the Geno2pheno software and the coreceptor usage predicted directly from the sequence.
Baseline and/or when failing therapy
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Must have quantifiable HIV-1 viral load.
HIV tropism test (V3 loop) is referral only.
Record last updated
August 21, 2025
Sample Container
4ml EDTA Vacutainers (Lavender top)
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Test Results
Yes, we have a Pathology User Guide
Yes. Please email your request to Imperial.nwlpcustomerservice@nhs.net
Results are communicated to clinical staff and are normally not communicated direct to patients either on telephone requests or in written report. If you need to contact us please click here to view the contact details page
Please contact the Customer Service Team Monday to Friday from 8:30am – 6:00pm on 0203 313 5353. Alternatively, see the Pathology User Guide for how to contact the relevant department. If advice is not urgent you can also email your query to Imperial.nwlpcustomerservice@nhs.net
Additional tests may be added by discussion with the relevant laboratory. The time limit for adding additional tests to a sample already received in the laboratory will depend on the type of sample and the department it was sent to.
Information on the repertoire of tests performed by pathology, including reference ranges, turnaround times and specimen requirements, can be found in the test directory.
Phlebotomy services are not managed by NWLP. For further information please see:
Imperial College Healthcare Trust Phlebotomy services
Chelsea and Westminster Hospital NHS Foundation Trust Phlebotomy services
NWLP operates UKAS accredited medical laboratories as per the references below. The current scope of accreditation for all NWLP’s laboratories can be found on the UKAS website.
See the following UKAS ref numbers:
- Clinical Biochemistry Ref: 8673
- Haematology and Blood Transfusion Ref: 8674
- Infection & Immunity Sciences (Including Immunology, Virology, Microbiology and Histocompatibility and Immunogenetics ) Ref: 8659
- Cellular Pathology (Including Histopathology, Cytology and Molecular Pathology) Ref: 9615
If you require copies of our certificate of accreditation and associated documentation please contact Imperial.nwlpcustomerservice@nhs.net.
UKAS requires the laboratories to be accredited for a particular repertoire/scope (ISO15189), any changes or additions to repertoire require assessment by UKAS (extension to scope).
The BD Hospital Tube Guide, BD GP Tube Guide and BD Paediatric Tube Guide provide visual references to the correct tube types and collection instructions.
Home testing
INSTRUCTION SHEET FOR BLOOD SAMPLE COLLECTION
We also have two instruction videos available (one with subtitles and one without) – please click on the links to view the videos on Google.
Our accreditations
Upholding excellence in diagnostic standards
Our laboratories are accredited by the UK Accreditation Service (UKAS) against the international standard ISO15189:2022. UKAS is the accreditation body for the UK that assesses medical laboratories.
Find out more about our accreditations on the UKAS website.
UKAS website