New England Journal of Medicine AUGUST 27, 2015

Initiation of Antiretroviral Therapy in Early Asymptomatic HIV Infection

The INSIGHT START Study Group (Lundgren JD, et al.)

Bottom Line

The START trial provided definitive, randomized clinical trial evidence that initiating antiretroviral therapy (ART) immediately in HIV-positive adults with CD4+ counts above 500 cells/mm³ significantly reduces the risk of serious AIDS-related events, non-AIDS-related illnesses, and death compared to deferring treatment until CD4+ counts decline to 350 cells/mm³.

Key Findings

1. The primary composite endpoint (serious AIDS-related events, serious non-AIDS-related events, or death) occurred in 1.8% of the immediate treatment group compared to 4.1% in the deferred treatment group.

2. Immediate ART initiation was associated with a 57% reduction in the risk of the primary outcome compared to deferred treatment (Hazard Ratio 0.43; 95% CI 0.30–0.62; P<0.001).

3. Benefits were driven by both a 72% reduction in serious AIDS-defining events and a 39% reduction in serious non-AIDS events, particularly non-AIDS-defining cancers.

4. The reduction in risk was observed consistently across various subgroups, including sex, age, baseline CD4+ cell count, and geographic region.

Study Design

Design

RCT

Open-Label

Sample

4,685

Patients

Duration

3 yr

Median

Setting

Multicenter, international

Population HIV-positive, antiretroviral-naive adults (age ≥18) with a baseline CD4+ T-cell count >500 cells/mm³.

Intervention Immediate initiation of antiretroviral therapy upon enrollment.

Comparator Deferred initiation of antiretroviral therapy until the CD4+ count declined to <350 cells/mm³ or the development of AIDS.

Outcome Composite of any serious AIDS-defining event, serious non-AIDS-defining event (major cardiovascular disease, end-stage renal disease, liver disease, non-AIDS-defining cancer), or death from any cause.

Study Limitations

• The study was stopped early by the Data Safety Monitoring Board, which may have led to an overestimation of the magnitude of the effect size.

• The median follow-up of three years, while sufficient for identifying initial clinical benefits, does not capture the very long-term safety profile or potential cumulative toxicities of lifelong, early-initiated ART.

• While the study included a diverse international population, the absolute event rates in both groups were low, reflecting the relatively healthy baseline population.

• The trial did not compare immediate initiation to intermediate thresholds (e.g., waiting for CD4+ < 500 cells/mm³), which were standard in some regions at the time.

Clinical Significance

The results of the START trial fundamentally shifted global HIV treatment guidelines, moving from the previous standard of deferring ART until CD4+ counts dropped to specific thresholds to a 'treat all' approach. This change has improved individual patient morbidity outcomes and leveraged the secondary prevention benefit of treatment as prevention (TasP), thereby reducing community-level HIV transmission.

Historical Context

Prior to this trial, the optimal timing for starting ART in asymptomatic individuals with high CD4+ cell counts was a subject of intense debate. Earlier guidelines favored waiting to avoid potential medication toxicities, drug resistance, and long-term adherence challenges. Observational studies suggested benefits of early treatment, but START was the first large-scale, randomized trial to provide high-level evidence confirming that the clinical benefits of early viral suppression outweigh the potential risks.

Guided Discussion

High-yield insights from every perspective

Med Student

Medical Student

How does the pathophysiology of chronic HIV infection explain why starting antiretroviral therapy (ART) at high CD4+ counts (>500 cells/mm³) reduces non-AIDS-related events such as cardiovascular disease and malignancy?

Key Response

Even at high CD4+ counts, untreated HIV replication causes persistent systemic inflammation and chronic immune activation. This inflammatory state accelerates atherosclerosis, increases the risk of certain cancers, and causes end-organ damage. The START trial demonstrated that immediate ART suppresses viral replication earlier, thereby mitigating this 'inflamm-aging' process and reducing non-AIDS morbidity.

Resident

An asymptomatic patient newly diagnosed with HIV has a CD4+ count of 800 cells/mm³. Based on the START trial results, how would you counsel the patient regarding the 'wait and see' approach previously used in clinical practice?

Key Response

The START trial provided definitive evidence that deferring ART until the CD4+ count drops below 350 cells/mm³ significantly increases the risk of both serious AIDS and non-AIDS events. Residents should counsel patients that immediate initiation reduces the risk of serious illness by over 50% compared to deferred treatment, regardless of the absence of symptoms.

Fellow

The START trial observed a benefit for immediate ART across diverse geographic regions. How did the specific composition of the primary endpoint (serious AIDS vs. serious non-AIDS events) differ between high-income and low-to-middle-income countries, and what does this imply for global HIV management?

Key Response

While the overall benefit was consistent, the specific events varied; AIDS-related events (like tuberculosis) were more frequent in low-income settings, whereas non-AIDS events (like cardiovascular disease) were more prominent in high-income settings. This implies that while the 'Treat All' strategy is globally applicable, clinicians must still tailor co-morbidity screening to the patient's specific epidemiological risk factors.

Attending

Before the START trial, the 'threshold' for ART was a subject of intense debate due to concerns about cumulative drug toxicity. How should this study change your teaching approach when discussing the risk-benefit ratio of lifelong ART in young, otherwise healthy patients?

Key Response

The trial shifted the paradigm from 'avoiding drug toxicity' to 'preventing irreversible immune damage.' The attending should emphasize that the risks of untreated HIV (even at high CD4+ counts) far exceed the risks of modern, less-toxic ART regimens. Teaching should focus on the fact that the most 'toxic' element in the patient's system is the virus itself, not the medication.

Scholarly Review

Critical appraisal through the lens of expert reviewers and guideline development

PhD

The START trial was a large-scale, international randomized controlled trial (RCT) stopped early by the DSMB. Critique the potential for 'overestimation of effect' in trials stopped early for benefit, and discuss how the trial's use of a composite primary endpoint might complicate the interpretation of mortality benefits.

Key Response

Trials stopped early can suffer from 'random highs' where the effect size is exaggerated because of the truncated follow-up. However, the START trial's high p-values (p < 0.001) and consistency across individual components of the composite endpoint (AIDS, non-AIDS, and death) suggest a robust effect. A PhD would note that while the composite endpoint increases statistical power, it can mask which specific outcomes are most influenced by the intervention unless subgroup analyses are rigorous.

Journal Editor

As a reviewer, if you were evaluating the START trial's methodology, how would you address the potential for bias introduced by the open-label design, and did the use of an independent end-point adjudication committee sufficiently mitigate this concern?

Key Response

Open-label trials are susceptible to performance and detection bias. However, because the primary endpoints (e.g., death, malignancy, specific AIDS-defining illnesses) were objective and adjudicated by a blinded committee unaware of treatment assignment, the internal validity remains high. Editors look for this 'blinded adjudication' as a hallmark of rigor in non-blinded clinical trials.

Guideline Committee

How did the START trial resolve the discrepancies between the DHHS and WHO guidelines regarding the CD4+ threshold for ART initiation, and what is the current 'Strength of Recommendation' for treating all HIV-positive individuals regardless of CD4+ count?

Key Response

Prior to START, guidelines were hesitant to recommend ART above 500 cells/mm³ due to lack of RCT evidence. START provided Level A, Strength I evidence, leading to a global consensus. Current DHHS and WHO guidelines now recommend ART for all HIV-infected individuals regardless of CD4+ count (the 'Treat All' recommendation), primarily to improve individual health outcomes as demonstrated in START, and secondarily to prevent transmission (TasP).

Clinical Landscape

Noteworthy Related Trials

2006

SMART Trial

n = 5,472 · NEJM

Tested

Episodic (drug conservation) ART strategy

Population

HIV-infected adults on ART

Comparator

Continuous ART

Endpoint

Opportunistic disease or death from any cause

Key result: The episodic strategy was associated with a higher risk of disease progression or death compared to continuous therapy.

2011

HPTN 052 Trial

n = 1,763 · NEJM

Tested

Early ART initiation

Population

HIV-serodiscordant couples

Comparator

Delayed ART initiation

Endpoint

Linked HIV transmission to the uninfected partner

Key result: Early initiation of ART reduced the risk of HIV transmission to uninfected partners by 96%.

2015

TEMPRANO ANRS 12136 Trial

n = 2,056 · NEJM

Tested

Immediate ART initiation

Population

HIV-infected adults with CD4 counts above 500 cells/mm3

Comparator

Deferred ART based on WHO criteria

Endpoint

Composite of all-cause mortality, AIDS-defining disease, non-AIDS-defining cancer, or invasive bacterial disease

Key result: Immediate initiation of ART resulted in a significantly lower risk of severe HIV-related events compared to deferred treatment.

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