Measurement Bias in Documentation of Social Risk Among Medicare Beneficiaries

Are documentation patterns for Z codes, which are used to capture social risk, susceptible to measurement bias relative to clinical complexity and historical health care utilization?In this cohort study of more than 7 million hospitalized Medicare beneficiaries in 2022, Z codes were used more often for less clinically complex patients and patients with higher levels of historical health care utilization. These patterns lead to a spurious negative association between documented social risk and predicted mortality.Existing documentation patterns for social risk are susceptible to measurement bias through multiple mechanisms and have important implications for risk adjustment, value-based payment, and health care resource allocation.

Corresponding Author: Paula Chatterjee, MD, MPH, General Internal Medicine, University of Pennsylvania, 423 Guardian Dr, Blockley Hall, Room 1318, Philadelphia, PA 19104 (pchat@pennmedicine.upenn.edu).

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