Definition and description of potential loss of each step of the cascade framework
| Component | Definition | Potential loss of health benefits |
| Target population | All who need a service/intervention | |
| Service contact | Proportion among those in need (the target population) who visit a health service. | Service access, awareness of services and service acceptability. Lack of access to services can occur because of structural (eg, facilities are too far or not open), financial or other obstacles. Individuals may be unaware of the need for care or that services exist for the conditions they have (eg, asymptomatic HIV infection or hypertension). And, people may opt not to use services because of perceived low quality, or preferred use of other sources of treatment (eg, traditional providers). |
| Likelihood of services | Proportion who visit a health facility or provider that is ‘ready’ (ie, all necessary inputs are available) to deliver the required services among those in need. This is also referred to as as input-adjusted coverage. | Service readiness or inputs: services cannot be provided as recommended if essential inputs are unavailable and inadequate (eg, facilities are not adequately stocked with essential medicines and equipment or basic running water and electricity, there are not enough trained health workers, etc). |
| Crude coverage | Proportion of the target population who receive a needed health intervention. | A health service is visited and all needed inputs are available for delivering the relevant intervention, but the intervention is not given. This may refer to the condition for which the individual sought health services, but may also be other opportunities related to, for instance, child vaccination. |
| Quality-adjusted coverage | Proportion of the target population receiving the service according to recommended standards (provider adherence to standards). | Interventions can only result in the intended health benefit if they are delivered in a respectful, timely fashion and according to standards and recommended guidance. Providers can also harm patients through the prescription of incorrect treatment. |
| User-adherence-adjusted coverage | Proportion of the target population receiving the service according to recommended standards and adhering to the treatment guidelines. | Several interventions require adherence of the user home treatment (eg, ARV therapy, antibiotic therapy, family planning methods) to maximise the effectiveness of treatment. |
| Outcome-adjusted coverage | Proportion of the target population experiencing the health gains from the service. This is also referred to as effective coverage. The framework proposes to use effective coverage only for the outcome-based coverage. The other levels of coverage are quality-adjusted measures of coverage. According to WHO, quality of care is the extent to which healthcare services provided to individuals and patient populations improve desired health outcomes. This definition implies a causal association of care received and impact, and is consistent with outcome-based definition of effective coverage. | Treatments have variable levels of efficacy, which implies that even if all standards are followed, health gains will be less than 100%. This applies to vaccines, family planning methods, antibiotics, etc. |
ARV, antiretroviral.