More Drug Resistance About

posted: 27/10/2010

There seems to be more transmitted drug-resistant HIV in the UK than we think, investigators say in HIV Medicine. The usual tests found 13% of undiagnosed HIV-positive gay men have drug-resistant virus. However, using more sensitive tests the researchers found 19% have become infected with drug resistant HIV.
 

Avoiding resistance

HIV treatment drug resistance is reduced by careful taking of HIV treatment, which is known as good adherence. Information and advice about better treatment taking and on adherence is in this booklet from NAM.

Rise and fall of resistance
The proportion of people who have become infected with drug-resistant HIV in the UK peaked at 12% in 2002. Better HIV treatment and care since then means this fell to 8% by 2006.

Resistance: test and treat

Everyone should be tested for drug resistance at the time of their HIV diagnosis. Drug resistance is measured at the time of HIV diagnosis because it becomes harder to find later. 

Even a little drug resistance reduces how well anti-HIV treatments will work. Knowing at the start what drugs someone’s HIV is already resistant to helps doctors and patients choose their personal best combination of HIV treatment drugs.

After treatment has begun if the treatment needs to be changed for any reason, there is a new online tool for deciding the best alternatives based on any drug resistance: HIV Treatment Response Prediction System (HIV-TRePS). 

Ordinary drug resistance tests not enough
The tests used normally to find resistance are only able to detect the main resistance types each person has. An international team of investigators wanted to see if a more sensitive test would find more resistance.

They tested 165 blood samples (anonymous) from undiagnosed gay men who used UK sexual health clinics between 2003 and 2006. None of the men knew they have HIV.

Sensitive tests find more

The samples were tested using both the normal method, and with a much more sensitive test that can find small amounts of the mutations resistant to first-line anti-HIV drugs.

Using the standard test, 21 samples (13%) were found with some drug resistance. This increased to 32 samples (19%) when the sensitive assay was used. This 45% increase in resistance levels was highly statistically significant.
 

Mutations found
They also looked for specific mutations.

• The standard test showed that 6% of patients had the K103N mutation (meaning resistance to efavirenz), and this rose to 7% with the more sensitive assay. This is not a significant difference.
• They did not find anyone with the Y181C mutation (resistant to efavirenz and nevirapine).
• One man had the M184V mutation (and resistance to 3TC or FTC). But this increased from 1 man (0.6%) to 13 men (8%) when both tests were used. This is highly statistically significant.

“The findings ... support the suggestion that M184V is as likely to be transmitted as other mutations”, write the study authors, adding, “this study contributes evidence to support the inclusion of minority assays for M184V surveillance.”

Rising drug resistance
Resistance rose by calendar year according to both methods. The standard test found 15% of samples in 2003 were drug resistant, and this rose to 19% using the sensitive test. In 2006 the standard test showed 10% of men have drug resistance, but this doubles when using both tests (highly statistically significant).
 

Is resistance still rising?
Resistance was found in 19% of undiagnosed gay men who were recently infected with HIV, and in 20% of those with long-standing infections. It appears drug resistance is still falling.

Source with reference

article abstract

Better treatment taking advice to avoid resistance

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