POPH90068 Chap.7 HIV Cascade and Prevention
HIV Cascade and Prevention
The HIV cascade arranges diagnosis, linkage, retention, treatment and viral suppression as sequential coverage stages. Differences between adjacent stages locate distinct service gaps and prevent a broad target from becoming a generic intervention. Combination prevention joins biomedical tools with accessible services, adherence, retention and social conditions.
A strong analysis defines denominators, identifies the transition that needs repair and keeps conclusions at the scale actually measured. Counts and conditional percentages are read together so a strong later stage does not hide losses before entry. Each proposed response is tied to one transition, an early process signal, an equity measure and a plausible downstream benefit.
What this chapter covers
- 01
Cascade stage definitions
- 02
Relative and population denominators
- 03
Diagnosis and linkage gaps
- 04
Retention and viral suppression
- 05
Combination prevention
- 06
Matched service interventions
Worked example · free
Repair a linkage gap
- 1Define the transition from diagnosis to linked care.
- 1Identify barriers such as referral complexity, cost, travel or stigma.
- 1Use navigation, booked appointments and barrier support rather than a broad testing campaign.
- 1Measure linkage within a defined interval and time to first appointment.
Key terms
- Cascade
- A sequence of coverage stages used to locate losses in care or prevention.
- Linkage
- Successful connection from diagnosis or referral to an appropriate care service.
- Retention
- Continued engagement with care across a defined period.
- Viral suppression
- Control of HIV replication to the threshold defined by the clinical measure.
- Combination prevention
- The coordinated use of biomedical, behavioural and structural approaches.
HIV Cascade and Prevention FAQ
Why do cascade denominators matter?
A percentage may use the previous stage or the estimated full population as its denominator. Those choices yield different values, so comparisons require the same definition and time window.
How is the largest cascade gap used?
Define the two adjacent stages, investigate barriers to that transition and select a delivery change capable of moving it. Then evaluate conversion and delay rather than relying on broad activity counts.
Why is combination prevention necessary?
Tools operate through different mechanisms and depend on access, uptake, adherence and retention. Social and service barriers can prevent biological efficacy from becoming population benefit.
Assessment move
Redraw the cascade with blank labels and define every numerator and denominator. For each possible gap, propose a different matched response: access to testing, supported linkage, retention assistance or adherence and treatment support. Add one process measure, one equity measure and one time measure. Practise ending with a bounded inference, such as improved linkage rather than reduced population incidence.
This stops targets from being treated as explanations and makes the intervention logic visible. Treat the cascade as linked conditional transitions. For each stage, specify who enters the denominator, what event places someone in the numerator and the period over which the measure is calculated. Do not compare percentages until definitions and populations are aligned.
A high proportion at a later stage may coexist with substantial loss earlier because people who never entered care are absent from that denominator. Redraw the pathway with counts as well as percentages to make the size of each gap visible. Match interventions to the location of loss. If the gap precedes diagnosis, examine access, testing offers, acceptability and coverage.
If it lies between diagnosis and care, focus on supported linkage and the handover process. If it occurs later, examine retention, continuity, adherence support and service conditions. Avoid offering the same education campaign at every stage. Write the mechanism that connects the proposed response to the specified transition and name an early process indicator that can show whether delivery occurred.
Add prevention choices without collapsing them into a single list. For each option supplied in the scenario, identify eligibility, the decision or behaviour required, the service support needed and the outcome it most directly influences. Consider combination approaches when barriers occur at different points, but give every component a defined role.
State where shared decision-making matters and where messages could create false reassurance or exclusion. Keep product efficacy separate from uptake, persistence and population coverage. Audit distribution at every step. Compare who is offered testing, who completes it, who links to care and who remains engaged, using subgroup measures that are ethically justified and safe to collect.
An overall cascade can improve while a particular population falls further behind. Add a qualitative question about why a transition failed, because an administrative count rarely distinguishes cost, stigma, inconvenient service design, distrust or competing priorities. Involve affected communities in interpreting gaps and choosing responses. Close practice answers with an inference ladder.
The strongest immediate claim may be better offer coverage, faster linkage or improved retention, not reduced incidence. State the observed stage, the plausible downstream benefit and the extra evidence needed to establish that benefit. Then specify a review point at which the team would continue, adapt or stop the intervention.
This makes cascade reasoning measurable and prevents aspirational targets from being treated as evidence of causation.
