Dear Forum Members,
 
Patients taking modern antiretroviral regimens still have a good chance of
maintaining an undetectable viral load if their adherence is below 95%, Spanish
researchers report in the October edition of AIDS Research and Human
Retroviruses. They found that patients taking HIV treatment based on either a
non-nucleoside reverse transcriptase inhibitor (NNRTI) or a ritonavir-boosted
protease inhibitor at an adherence rate of only 80% was associated with a risk
of virological failure below 10%.

This is the equivalent of missing no more than one dose in five of a once-daily
combination. Ninety per cent adherence is the equivalent of missing one dose in
ten - a substantial difference in the frequency of missed doses.

But the study’s authors emphasise that the goal should still be to achieve the
highest possible rate of treatment adherence as there were very low rates of
treatment failure even amongst patients whose level of adherence was at least
90%.

Antiretroviral therapy provides HIV-positive individuals with the chance of
living a long and healthy life. However, HIV treatment is a life-long commitment
and can involve side-effects. Furthermore, many patients find it difficult to
sustain high levels of adherence to their antiretroviral therapy, and poor
treatment adherence is associated with the emergence of drug-resistant HIV as
well as an increased risk of HIV-related illness and death.

It is generally said that it is necessary to take at least 95% of HIV treatment
doses at the right time and in the right way for antiretroviral therapy to have
the best chance of achieving and maintaining suppression of HIV.

However, this estimate was based upon outcomes seen in patients taking older
unboosted protease inhibitors, a class of drugs that is no longer recommended.
Therefore researchers in Barcelona studied the level of adherence needed to
maintain an undetectable viral load in patients taking antiretroviral therapy
based upon NNRTIs or boosted protease inhibitors.

Their research involved 1142 treatment-naĂŻve and treatment-experienced patients
who were prescribed antiretroviral therapy between 2004 and 2005. All the
patients had achieved an undetectable viral load. The study lasted one year.

These patients were divided according to the type of antiretroviral regimen they
were taking: unboosted protease inhibitor (11%); boosted protease inhibitor
(31%); and NNRTI (58%). Adherence was assessed by pill count during routine
clinic appointments. The researchers compared the risk of viral load increasing
to detectable for each of the drug classes at various levels of adherence: below
70%; 70-80%; 80-90% and above 90%. They also examined whether any treatment or
patient characteristics were associated with adherence and outcome.

Most of the patients (1059) maintained an undetectable viral load for the
duration of the study, and their mean level of adherence was 96%. Mean adherence
for the 83 individuals who experienced a breakthrough in their viral load was
76%.

Compared to patients with 90% adherence or better, the risk of virologic failure
was 9% for those with adherence between 80-90%, increasing to 46% of those with
adherence between 70-80% and 77% for those who took below 70% of their doses.

At all levels of adherence below 90%, those taking an unboosted protease
inhibitor were the group most likely to develop resistance (100% failure rate
for adherence below 70%, 71%failure rate for adherence between 70-79%, 24%
failure rate for adherence between 80-89%).

Although the failure rate for patients taking a boosted protease inhibitor and
adherence below 90% was higher for patients taking a boosted protease inhibitor
than those taking an NNRTI, it was not significantly so (below 70%, 50% vs. 35%;
between 70-79%, 37% vs. 24%, between 80-89%, 9% vs. 6%).

The only factors associated with adherence were the number of pills (with the
chances of adherence decreasing significantly as the number of pills increased,
p < 0.001), and number of daily doses. However, although adherence was poorer
amongst patients taking their treatment three times a day, there were no
significant differences between patients taking their treatment once-daily and
twice-daily.

Our data show that virologic success is possible with less than 95%
adherence”, conclude the investigators, adding, “for patients taking NNRTI-
or boosted protease inhibitor-based regimens with adherence rates of 80%, the
failure rate is less than 10%.

However, the investigators found extremely low rates of treatment failure for
patients with adherence above 90% (1% for those taking an unboosted protease
inhibitor, 0.5% for those taking a boosted protease inhibitor and 1.4% for those
taking an NNRTI) and therefore conclude, that the goal should still be to
achieve “the highest rate of adherence possible.”

Reference

Marin M. Relationship between adherence level, type of antiretroviral regimen,
and plasma HIV type 1 RNA viral load: a prospective cohort study. AIDS Research
and Human Retroviruses 24: 1263-68, 2008.

Dr Diwakar Tejaswi
MBBS(Gold Medalist); MCH; FCCP; Ph.D.
Family Physician and Medical Director
Regional AIDS Training Centre and Network in India(RATNEI)
International Health Organization
India Office: B-33, Indirapuri Colony, Patna 800014, India
Phone: +91-612-3299323 (O); 2586788 (Telefax O); Clinic- Telefax:
+91-612-2206964; Mobile: +91-9835078298; Res: +91-612-2351771
www.ihousa.org