Situation: The Rural Health Unit (RHU) nurse extends services to population groups the program has reached poorly: key populations for HIV and an indigenous community in a geographically isolated and disadvantaged area (GIDA). The nurse reviews this year's HIV cascade-of-care data for men who have sex with men in the municipality. Assume the estimate is reliable. Estimated men living with HIV: 200 Diagnosed and aware of their status: 170 Started on antiretroviral therapy (ART): 90 Virally suppressed: 81 Which action should be the nurse's PRIORITY?

Each step of the cascade is compared with the step before it. Diagnosis reaches 170 of 200 (85%, a gap of 30 men), and viral suppression reaches 81 of 90 on ART (90%, a gap of 9), but only 90 of 170 diagnosed men have started ART (53%, a gap of 80). The largest break is linkage, so the priority is to trace diagnosed men who are not on ART and link them to a treatment hub for rapid ART start.

The HIV care cascade is a population-level framework that visualizes the sequential steps a person must pass through to achieve viral suppression: diagnosis, linkage to care, initiation of ART, and ultimately viral suppression ^[2]. When a nurse reviews cascade data, the goal is not to celebrate the steps that are working well but to identify the step with the largest drop-off, because that is where the greatest number of preventable adverse outcomes is concentrated ^[4].

In this municipality, the cascade can be expressed as three consecutive transitions. The first transition is from estimated infection to diagnosis: 200 estimated men living with HIV, of whom 170 are diagnosed, leaving a gap of 30 undiagnosed men. The second transition is from diagnosis to ART initiation: 170 diagnosed, but only 90 started on ART, leaving a gap of 80 men. The third transition is from ART initiation to viral suppression: 90 on ART, with 81 virally suppressed, leaving a gap of 9 men.

When each gap is expressed as a proportion of the preceding step, the diagnosis gap is 15% of the estimated total, the viral suppression gap is 10% of those on ART, but the ART initiation gap is 47% of those already diagnosed. The largest break in this cascade is the linkage-to-ART step, not the diagnosis step and not the adherence step.

This interpretation aligns with the cascade framework described in the literature. The HIV treatment cascade is defined by five main steps—diagnosis, linkage to care, retention in care, ART adherence, and viral suppression—and each step is measured against the step immediately before it ^[2]. When a single step shows a disproportionately large drop, that step represents the most efficient target for programmatic intervention, because the people lost at that point have already been identified by the health system and can be reached directly ^[1][4].

In this scenario, the 80 diagnosed men who have not started ART are already known to the system. They have a confirmed diagnosis, which means the health unit has a name, a record, and a point of contact for each of them. Tracing these men and linking them to a treatment hub for rapid ART initiation addresses the largest gap with the most actionable population. By contrast, the 30 undiagnosed men are unknown to the system, and finding them requires outreach, testing, and engagement strategies that are slower and less certain to yield immediate clinical benefit .

Key point! The priority is determined by comparing each cascade gap to the step immediately before it, not by comparing raw numbers across non-adjacent steps. A gap of 80 out of 170 diagnosed men is proportionally larger than a gap of 30 out of 200 estimated men.

Adherence counseling for the 90 men already on ART would address only the 9 men who are not suppressed, a much smaller group. Expanding condom and pre-exposure prophylaxis supply targets prevention, which is important but does not address the men already living with HIV who are not receiving treatment. Expanding peer-led testing outreach targets the undiagnosed, but the undiagnosed gap is smaller than the linkage gap. Watch out! Do not choose the prevention or testing option simply because it sounds proactive; the cascade data point to a specific, larger failure at the linkage step.

The dynamic nature of the cascade also supports this priority. Real-world engagement with HIV care is not perfectly linear, and patients may move in and out of care over time ^[1]. However, when a cross-sectional cascade shows a large linkage gap, the most direct and evidence-aligned response is to re-engage the people who have already entered the system but have not progressed to treatment ^[2][4].

Step	Numerator	Denominator	Gap	Gap as % of preceding step
Diagnosis	170	200 estimated	30	15%
ART initiation	90	170 diagnosed	80	47%
Viral suppression	81	90 on ART	9	10%

The largest proportional loss occurs between diagnosis and ART initiation. The nurse should therefore prioritize tracing the 80 diagnosed men who have not started ART and rapidly linking them to the treatment hub for ART initiation ^[2][4].