HCV Drug Resistance Test
HCV Drug Resistance Test
Hepatitis C is a chronic bloodborne liver infection that affects an estimated 6–12 million individuals in India. The current standard of care for patients with HCV involves interferon-free, direct-acting antivirals (DAAs) drug combination therapy. These drugs work by targeting specific proteins necessary for the virus to replicate and cause infection. However, issues such as patients not taking medications as prescribed and the virus developing resistance before treatment compromise the effectiveness of HCV antiviral therapy.
Mutations, known as resistance-associated substitutions (RASs), can occur in specific regions of the HCV genome either naturally or as a result of treatment, causing the development of antiviral resistance among the virus, with consequent treatment failure.
The Hepatitis C Virus (HCV) Drug Resistance Assay is a blood test that utilizes polymerase chain reaction (PCR) amplification and DNA next-generation sequencing techniques to identify and detect RASs in the NS3, NS5A, and NS5B genomic regions of some HCV genotypes. If a specific RAS is present, it signifies resistance to a particular antiviral drug for HCV.
Knowledge of RASs helps clinicians choose the most effective treatment options for patients, improving health outcomes.
This test is explicitly conducted on samples that have confirmed HCV genotypes and a detectable viral load of ≥500 IU/ml in the preceding 2-4 weeks.
What is the HCV Drug Resistance test Used For?
The HCV Drug Resistant test is used
To see whether or not people with HCV infection are treatable before starting the therapy or restarting treatment after it didn't work the first time.
To guide selection of antiviral therapy in patients with HCV genotype 1 and 3
To predict the likelihood of cure in patients with chronic HCV infection
For monitoring patient’s response to HCV drugs
Symptoms of Hepatitis C infection
Most people with HCV lack symptoms. Yet, a few may experience
Jaundice (yellow discoloration of the eye and skin)
Tiredness
Nausea and Vomiting
Fever
Pain in the upper right part of the belly
Joint pain
Dark-colored urine and stool
Preparation for Test
The HCV drug resistance assay does not require any special preparation. But let your doctor know your medical history and the medications and supplements you take to avoid ambiguous test results.
Interpretation of Test Results
HCV drug resistance results are typically reported as "resistance probable" or "not detected/undetermined" to denote viral susceptibility to each HCV antiviral drug.
When making therapeutic decisions, your doctor may consider resistance result in conjunction with your treatment history, clinical presentation, and other test markers.
Resistance probable
It indicates the presence of drug-specific mutations in the HCV sequences found in the patient's serum, which in turn suggests reduced susceptibility of the viral population to specific HCV antivirals.
Not detected/Undetermined
This result suggests that resistance to a particular HCV antiviral is unlikely, although it does not rule out the presence of reservoirs of HCV-resistant strains in the infected patient.
FAQs
What are direct-acting antivirals(DAAs)?
DAAs are medications meant to eradicate HCV infection by attacking more than one target required in viral replication. They are classified into four classes:
- NS3/4A protease inhibitors
- NS5A polymerase inhibitors
- NS5B nucleoside polymerase inhibitors
- NS5B non-nucleoside polymerase inhibitors
What factors can affect the HCV drug resistance test?
Many factors can affect the results of an HCV drug resistance test, such as a low HCV RNA load (< 500 IU/ML), inhibitors in the blood, atypical genome sequences from multiple genotypes, and HCV target sequences that are ambiguous or incomplete.
What are resistance-associated substitutions (RASs)?
A resistance-associated substitution describes amino acid substitutions in the HCV genome sequence that make the virus less susceptible to one or more antiviral drugs, leading to treatment failure.
How are the HCV drug resistance assays performed?
Depending on the test selected, RT-PCR with genotype-specific primers amplifies either the NS3/4A, NS5A, or NB5B region of HCV from patient plasma samples. Then, the obtained nucleotide sequences are determined using NGS methods and compared to wild-type HCV reference sequences. Drug resistance is interpreted and reported for each antiviral drug by analyzing the amino acid difference from the reference sequences.
How often the HCV drug resistance testing is performed?
Drug resistance tests are typically conducted before starting antiviral therapy for chronic HCV infections. This helps doctors choose the most effective antiviral treatment. However, your doctor may also recommend a resistance test if you did not respond to DAA-based therapy in the past and are being assessed for retreatment. The goal is to detect any new mutations linked to HCV antiviral medications.
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