Population risk stratification is a systematic, population-wide approach used to predict future needs, whether morbidity, resource consumption, costs, adverse events (unplanned admissions that are potentially avoidable) or other risks.
Although stratification makes it possible to calculate current resource consumption, its great value is due to the estimation of future resource consumption (based on historical data).
In practical terms, stratification classifies and groups patients, to identify subpopulations with 
comparable risk.
Typically the stratification follows the Keiser Permanent pyramid logic.
The highest-risk subpopulation comprises only a small percentage of the total population (5%), followed by a lower-risk group (about 20%), then a low-risk group (about 75% of the population).
Risk adjustment is a mechanism that guarantees an incentive to provide care to patients with a high risk of consumption in health care, avoiding the adverse selection of users (ie, the preferential choice of patients with less complexity, which means less coexistence of multiple disease conditions).
The care provider will be indifferent to having on his list patients at high risk or with low risk of consumption of care, as the adjustment for risk guarantees an adequacy of financial resources according to the characteristics of the patient and the greater probability of consumption of care and financial resources (such as the elderly, chronically ill and with multiple pathologies and who, as a result, have higher health costs).
It allows for a positive discrimination of populations with higher levels of health needs, making a fairer allocation of resources by guaranteeing the care provider a higher payment if the probability of consumption of health care by patient is also higher
Within the scope of the Recovery and Resilience Plan, was published a strategy for risk stratifying the population, as a structuring factor in the organization of people centered integrated care and in the distribution of resources, whether physical, human or financial.
Click here to see the document.
PCI | Patient Complexity Index
The PCI is a risk stratification tool developed by ACSS, which calculates, for all users, a numerical value with predictive capacity of the use of health resources, specially calibrated for the use of medical resources in primary health care, in terms specified at https://sdm.min-saude.pt/bi.aspx?id_estr=1746.
This tool has already been analysed regarding its methodological and statistical robustness. The study was financed by the European Commission.
The report was produced by an independent entity and is available here.
Other Stratification Instruments
As part of a European project on stratification strategies and results (Activation of Stratification Strategies and Results of the interventions on frail patients of Healthcare Services – ASSEHS), it was published a dashboard that allows the comparison between different instruments.
