Social Determinants of Health Coding Among Hospital Visits Made by Adults With Cancer

Social determinants of health (SDOH) affect clinical outcomes among patients diagnosed with cancer. In 2015, International Classification of Diseases-10 diagnosis codes starting with Z prefix, or Z-codes, were introduced to capture SDOH complexity. We examined Z-code uptake for patients treated by an academic medical center and county safety-net health system and their comprehensive hospital visits from a regional health information exchange.

We identified adults age 18 years or older from two tumor registries, diagnosed from January 1, 2015, to December 31, 2023, and identifiably linked them to their longitudinal, comprehensive hospital visits. We characterized Z-code uptake trends as patients visited over 80 hospitals, for all payers including the uninsured.

We identified 57,598 patients with 181,684 associated ED and inpatient hospital discharges across more than 80 regional hospitals. Approximately 4.7% of patients had at least one Z-code entered during any hospital visit, and Z-codes were present in just 2.8% of all hospital discharges. Z-code use rose over time from 1.1% of visits in 2016 to 11.3% by 2023. Of the cohort, 23.9% were treated by the county safety-net system; 9.4% had Medicaid and 28.6% were uninsured/charity care at diagnosis; and 24.4% had advanced-stage disease. The most common Z-code was Z59 (housing and economic circumstances), accounting for 48.6% of all Z-codes. Documentation was nearly three-fold higher at the county safety-net system than at the academic center (8.6% v 2.9%; P < .001).

In a population-based sample of adults with cancer and their comprehensive hospital visits, Z-code use increased to over 11% of hospital visits by 2023, and housing and economic problems were most prominent. Future work should explore the validity of this coding at an individual patient level.