Risk-Weighted Impact: Reframing Risk Analyses for Medical Decisions

Developing precise metrics for clinical use is vital to translating outcomes data to practice. Risk probabilities, such as the complication rate of surgery or the lifetime risk of an aneurysm rupture, are widely used for counseling patients, but their comparison may be misleading if risks are spread over different time horizons. This study evaluates a new risk-assessment approach called risk-weighted impact (RWI) that applies event probabilities to estimate the average number of years of life impacted by event occurrence.

Decision-making policies based on RWI and cumulative lifetime event risk were applied to determine management in a simplified model of incidental cerebral aneurysms through Monte Carlo simulation (1000 iterations of 10 000 synthetic patients). In addition, a web-based application was created to simplify risk-assessment calculations and comparisons.

When treatment of incidental cerebral aneurysms was simulated using both risk assessment methods, there was disagreement in 25.2% (95% CI: 24.4%-26.1%) of cases, with the RWI policy preferring observation, while event-risk policy preferred intervention. In these patients, the number of poor outcomes was nearly the same, 110 (95% CI: 91-129) in RWI policy and 111 (95% CI: 90-132) in event-risk policy, but the RWI policy resulted in 874.8 fewer quality-adjusted life year lost (95% CI: 299.5-1466.6) due to adverse events occurring an average of 11.3 years later (95% CI: 8.2-14.1 years).

Only using cumulative lifetime event risks may understate the impact of an up-front treatment given that a larger proportion of risk is assumed at an earlier age, when more years of life are in jeopardy. RWI offers an alternative approach to thinking about risk, using the same inputs (event probabilities and life expectancy) to compare estimated patient impact. RWI is more aligned with clinical objectives and is a valuable metric for risk assessment and decision making.