Understanding the ICA/CCA Ratio in Cost-Effectiveness Analysis
The ICA/CCA Ratio, more commonly referred to in health economics as the Incremental Cost-Effectiveness Ratio (ICER), is a critical metric used to compare the economic value of two different interventions. It provides a numerical value representing the additional cost required to achieve one additional unit of effectiveness (such as a life year gained or a Quality-Adjusted Life Year, QALY).
The Mathematical Formula
The ratio is calculated by dividing the difference in costs by the difference in outcomes:
Ratio = (Cost_New – Cost_Standard) / (Effectiveness_New – Effectiveness_Standard)
How to Interpret Results
Low Ratio: Suggests the new intervention provides a high degree of extra benefit for a relatively low extra cost.
High Ratio: Indicates that the additional benefits come at a high financial premium.
Negative Ratio: This usually occurs in two scenarios:
The new intervention is cheaper and more effective (Dominant).
The new intervention is more expensive and less effective (Dominated).
Real-World Example
Imagine a standard medication costs $30,000 and provides a patient with 0.60 QALYs. A new biotech drug costs $50,000 but increases effectiveness to 0.85 QALYs.