Figure 1. Essence of the Person-Centered Treatment Approach.

A patient’s propensity for transfer is gauged according to observed and unobserved characteristics. Three patients (P, Q, and R) share the same propensity according to observed factors. However, the propensity for intensive care unit (ICU) transfer according to unobserved characteristics is low for patient Q, balanced for patient P, and high for patient R. An additional bed only affects the decision to transfer for P, the “marginal” patient. A, Patient P is marginal in that the propensity to transfer according to observed and unobserved characteristics is balanced. With 2 beds available, the marginal patient remains on the general ward. B, The additional bed availability (3 beds) encourages the decision to transfer the marginal patient (P→P′). C, For the marginal patient, we proxy the propensity for ICU transfer according to unobserved characteristics as the negative of the propensity due to observed characteristics. For this marginal patient, the treatment effect is estimated by accounting for observed and unobserved characteristics.