Overview
The HIV Genotyping and Drug Resistance Test is an advanced laboratory test that examines the genetic structure of the Human Immunodeficiency Virus (HIV) present in a person’s blood. HIV is a virus that can change and mutate as it multiplies inside the body. Some of these mutations can cause the virus to become resistant to antiretroviral drugs, meaning that the usual HIV medicines may not work as effectively.
This test plays a crucial role in modern HIV care because it helps doctors understand which medicines will work best for each patient. Since HIV treatment is long-term and requires the right combination of drugs, genotyping is an essential step in personalized treatment planning.
How HIV Mutations Develop Inside the Body
HIV is not produced by the human body. Instead, once HIV enters the bloodstream, it targets specific immune cells, mainly CD4 T-cells, and uses them to reproduce. During this replication process, the virus often makes copying errors in its genetic material (RNA). These errors are called mutations.
Some mutations are harmless, but others make the virus resistant to one or more antiretroviral medications. The HIV Genotyping Test identifies these mutations in the viral RNA and informs the healthcare provider about which drugs will no longer be effective.
Why HIV Genotyping Test is Important
This test is a key component of HIV management and is often done:
- Before starting HIV treatment (baseline testing)
- When viral load increases unexpectedly
- When treatment stops working
- During pregnancy, to ensure the chosen drugs prevent transmission to the baby
Main Functions and Importance
1. Detects Resistance Mutations
The primary purpose of this test is to identify specific genetic mutations in the HIV genome that make the virus resistant to medications. These mutations may affect drug classes like:
- NRTIs (Nucleoside Reverse Transcriptase Inhibitors)
- NNRTIs (Non-Nucleoside Reverse Transcriptase Inhibitors)
- PIs (Protease Inhibitors)
- INSTIs (Integrase Strand Transfer Inhibitors)
2. Helps in Choosing Effective Treatment
Treatment combinations vary from person to person. Based on the genotyping results, doctors can prescribe the best medication plan with the highest chance of success.
3. Prevents Drug Failure
If a patient unknowingly continues a medicine that no longer works due to mutations, the viral load can rise again. This test helps avoid that risk.
4. Supports Personalized Care
Not all patients respond to drugs in the same way. Genotyping allows individualized decision-making, resulting in better long-term outcomes.
Causes of Low/Negative Values
A “negative” result does not mean HIV is gone. It simply means:
- No resistance mutations were detected.
- The virus is still sensitive to the commonly used antiretroviral drugs.
- The patient is likely responding well to treatment.
- The viral load may be too low for the test to detect mutations.
In some cases, the viral load has to be above a certain level (usually >1,000 copies/mL) for the genotyping test to work accurately.
Symptoms of Low/Negative Values
There are no direct physical symptoms associated with a negative result.
However, it is actually a good sign, indicating that:
- The current treatment is effective.
- The virus has not developed resistance.
- No change in medication is needed.
Causes of High/Positive Values
A “positive” result means resistance mutations were detected. This can happen due to:
1. Frequent Viral Replication
If the virus is multiplying actively, mutation chances increase.
2. Poor Medication Adherence
Missing doses or irregular usage can allow the virus to adapt and become resistant.
3. Long-Term Use of the Same Drug Regimen
Over time, some strains naturally develop resistance to specific drug types.
4. Transmission of Resistant HIV
A person may acquire a strain of HIV that is already resistant to some medicines.
Symptoms of High/Positive Values
A positive drug resistance result may be associated with clinical signs such as:
- Persistent or recurring HIV-related symptoms
- Increasing viral load despite regular treatment
- A fall in CD4 count
- Opportunistic infections like:
- Fever
- Weight loss
- Chronic diarrhea
- Skin infections
- Fatigue
- Frequent respiratory infections
These signs indicate that treatment may not be working effectively.
Reference Range
There is no fixed numerical reference range for this test. Results are reported in two categories:
- “No resistance mutations detected”
– The virus is sensitive to available medications. - “Resistance mutations detected”
– Reports mention which drug classes are affected and which drugs may not work.
The laboratory report usually includes detailed mutation names such as K103N, M184V, etc., along with their clinical significance.
Sample Type
- Blood sample (plasma)
- Collected through a standard venous blood draw
The sample is then processed to extract viral RNA for genotyping.
Test Preparation
- No fasting required.
- Continue regular medications unless your doctor advises otherwise.
- Ensure you attend the test when viral load is detectable (not too low).
- Bring previous HIV treatment records if available.
When to Consult a Doctor
You should immediately consult a doctor if:
- Your viral load is increasing despite proper medication.
- You develop new HIV-related symptoms.
- Your CD4 count is falling suddenly.
- Your doctor recommends a change in your treatment plan.
- You are starting HIV treatment for the first time.
- You are pregnant and living with HIV.
Important Word Explanations
- Mutation: A change in the genetic material of the virus.
- Drug Resistance: When HIV stops responding to certain medicines.
- Viral Load: The amount of HIV in the blood.
- CD4 Cells: Immune cells that HIV attacks.
- Genotyping: Analyzing the virus’s genes to check for mutations.
- Antiretroviral Therapy (ART): Medicines used to control HIV.
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