Comparative effectiveness of immediate antiretroviral therapy versus CD4-based initiation in HIV-positive individuals in high-income countries: observational cohort study

BACKGROUND

Recommendations have differed nationally and internationally with respect to the best time to start antiretroviral therapy (ART). We compared effectiveness of three strategies for initiation of ART in high-income countries for HIV-positive individuals who do not have AIDS: immediate initiation, initiation at a CD4 count less than 500 cells per μL, and initiation at a CD4 count less than 350 cells per μL.

METHODS

We used data from the HIV-CAUSAL Collaboration of cohort studies in Europe and the USA. We included 55,826 individuals aged 18 years or older who were diagnosed with HIV-1 infection between January, 2000, and September, 2013, had not started ART, did not have AIDS, and had CD4 count and HIV-RNA viral load measurements within 6 months of HIV diagnosis. We estimated relative risks of death and of death or AIDS-defining illness, mean survival time, the proportion of individuals in need of ART, and the proportion of individuals with HIV-RNA viral load less than 50 copies per mL, as would have been recorded under each ART initiation strategy after 7 years of HIV diagnosis. We used the parametric g-formula to adjust for baseline and time-varying confounders.

FINDINGS

Median CD4 count at diagnosis of HIV infection was 376 cells per μL (IQR 222-551). Compared with immediate initiation, the estimated relative risk of death was 1·02 (95% CI 1·01-1·02) when ART was started at a CD4 count less than 500 cells per μL, and 1·06 (1·04-1·08) with initiation at a CD4 count less than 350 cells per μL. Corresponding estimates for death or AIDS-defining illness were 1·06 (1·06-1·07) and 1·20 (1·17-1·23), respectively. Compared with immediate initiation, the mean survival time at 7 years with a strategy of initiation at a CD4 count less than 500 cells per μL was 2 days shorter (95% CI 1-2) and at a CD4 count less than 350 cells per μL was 5 days shorter (4-6). 7 years after diagnosis of HIV, 100%, 98·7% (95% CI 98·6-98·7), and 92·6% (92·2-92·9) of individuals would have been in need of ART with immediate initiation, initiation at a CD4 count less than 500 cells per μL, and initiation at a CD4 count less than 350 cells per μL, respectively. Corresponding proportions of individuals with HIV-RNA viral load less than 50 copies per mL at 7 years were 87·3% (87·3-88·6), 87·4% (87·4-88·6), and 83·8% (83·6-84·9).

INTERPRETATION

The benefits of immediate initiation of ART, such as prolonged survival and AIDS-free survival and increased virological suppression, were small in this high-income setting with relatively low CD4 count at HIV diagnosis. The estimated beneficial effect on AIDS is less than in recently reported randomised trials. Increasing rates of HIV testing might be as important as a policy of early initiation of ART.

FUNDING

National Institutes of Health.

When to start antiretroviral therapy: as soon as possible

BACKGROUND

The debate regarding 'When to Start' antiretroviral therapy has raged since the introduction of zidovudine in 1987. Based on the entry criteria for the original Burroughs Wellcome 002 study, the field has been anchored to CD4 cell counts as the prime metric to indicate treatment initiation for asymptomatic individuals infected with Human Immunodeficiency Virus. The pendulum has swung back and forth based mostly on the relative efficacy, toxicity and convenience of available regimens.

DISCUSSION

In today's world, several factors have converged that compel us to initiate therapy as soon as possible: 1) The biology of viral replication (1 to 10 billion viruses per day) strongly suggests that we should be starting early. 2) Resultant inflammation from unchecked replication is associated with earlier onset of multiple co-morbid conditions. 3) The medications available today are more efficacious and less toxic than years past. 4) Clinical trials have demonstrated benefits for all but the highest CD4 strata (>500 cells/μl). 5) Some cohort studies have demonstrated the clear benefit of antiretroviral therapy at any CD4 count and no cohort studies have demonstrated that early therapy is more detrimental than late therapy at the population level. 6) In addition to the demonstrated and inferred benefits to the individual patient, we now have evidence of a Public Health benefit from earlier intervention: treatment is prevention.

SUMMARY

From a practical, common sense perspective we are talking about life-long therapy. Whether we start at a CD4 count of 732 cells/μl or 493 cells/μl, the patient will be on therapy for over 40 to 50 years. There does not seem to be much benefit in waiting and there likely is significant long-term harm. Do not wait. Treat early.

Effect of immediate initiation of antiretroviral treatment on the risk of acquired HIV drug resistance

OBJECTIVE

We estimated and compared the risk of clinically identified acquired drug resistance under immediate initiation [the currently recommended antiretroviral therapy (ART) initiation strategy], initiation with CD4 cell count less than 500 cells/μl and initiation with CD4 cell count less than 350 cells/μl.

DESIGN

Cohort study based on routinely collected data from the HIV-CAUSAL collaboration.

METHODS

For each individual, baseline was the earliest time when all eligibility criteria (ART-naive, AIDS free, and others) were met after 1999. Acquired drug resistance was defined using the Stanford classification as resistance to any antiretroviral drug that was clinically identified at least 6 months after ART initiation. We used the parametric g-formula to adjust for time-varying (CD4 cell count, HIV RNA, AIDS, ART regimen, and drug resistance testing) and baseline (calendar period, mode of acquisition, sex, age, geographical origin, ethnicity and cohort) characteristics.

RESULTS

In 50 981 eligible individuals, 10% had CD4 cell count more than 500 cells/μl at baseline, and 63% initiated ART during follow-up. Of 2672 tests for acquired drug resistance, 794 found resistance. The estimated 7-year risk (95% confidence interval) of acquired drug resistance was 3.2% (2.8,3.5) for immediate initiation, 3.1% (2.7,3.3) for initiation with CD4 cell count less than 500 cells/μl, and 2.8% (2.5,3.0) for initiation with CD4 cell count less than 350 cells/μl. In analyses restricted to individuals with baseline in 2005-2015, the corresponding estimates were 1.9% (1.8, 2.5), 1.9% (1.7, 2.4), and 1.8% (1.7, 2.2).

CONCLUSION

Our findings suggest that the risk of acquired drug resistance is very low, especially in recent calendar periods, and that immediate ART initiation only slightly increases the risk. It is unlikely that drug resistance will jeopardize the proven benefits of immediate ART initiation.

Effect of Immediate Initiation of Antiretroviral Treatment in HIV-Positive Individuals Aged 50 Years or Older

BACKGROUND

Clinical guidelines recommend immediate initiation of combined antiretroviral therapy for all HIV-positive individuals. However, those guidelines are based on trials of relatively young participants.

METHODS

We included HIV-positive antiretroviral therapy-naive, AIDS-free individuals aged 50-70 years after 2004 in the HIV-CAUSAL Collaboration. We used the parametric g-formula to estimate the 5-year risk of all-cause and non-AIDS mortality under (1) immediate initiation at baseline and initiation at CD4 count, (2) <500 cells/mm, and (3) <350 cells/mm. Results were presented separately for the general HIV population and for a US Veterans cohort with high mortality.

RESULTS

The study included 9596 individuals (28% US Veterans) with median (interquantile range) age of 55 (52-60) years and CD4 count of 336 (182-513) at baseline. The 5-year risk of all-cause mortality was 0.40% (95% confidence interval (CI): 0.10 to 0.71) lower for the general HIV population and 1.61% (95% CI: 0.79 to 2.67) lower for US Veterans when comparing immediate initiation vs initiation at CD4 <350 cells/mm. The 5-year risk of non-AIDS mortality was 0.17% (95% CI: -0.07 to 0.43) lower for the general HIV population and 1% (95% CI: 0.31 to 2.00) lower for US Veterans when comparing immediate initiation vs initiation at CD4 <350 cells/mm.

CONCLUSIONS

Immediate initiation seems to reduce all-cause and non-AIDS mortality in patients aged 50-70 years.