States that a natural relationship exists for each individual (or group of ind) between the frequency (observation) or the probability (prediction) of a morbid event without any treatment (Rc) and the frequency or probability of the same event with a treatment (Rt).
EM defines the relationship between the probability of disease-related events with (Rt) and without (Rt) therapy and can be calculated as a sum of differences for each patient.
EM is estimated by combining a formal model of the disease & therapy of interest with a Vpop representative of a specific geography or context. Sum of all clinical benefits of the treatment for each patient results in the Number of Prevented events (NPE).