Prevalence, Correlates and Predictive Value of ICD-10 Z Codes to Identify Social Determinants of Health That Affect Insured Adults’ Health and Health Care Use

In recent years, a growing understanding of the importance of social determinants of health (SDOH) has driven a flurry of efforts to identify and address health-related social needs in health care settings. One novel, national approach to identifying when SDOH influence demand for health care are SDOH-related Z codes (henceforth ‘Z codes’), which supersede the V codes used in the International Classification of Diseases (ICD), Ninth Revision coding architecture (1). Z codes were introduced with the ICD, Tenth Revision (ICD-10) coding architecture in October 2015, and identify reasons for encounters when circumstances other than a disease or injury are recorded as diagnoses or problems. Codes Z55-65, along with a few other ICD-10 codes, specifically identify socioeconomic and psychosocial circumstances, and identify SDOH-related factors that can affect health care use.

Project Summary

The proposed research offers an important opportunity to better understand very recent utilization of Z codes, beyond the initial two-year period following their introduction, and in both Medicare and non-Medicare populations. In addition, this research will provide important documentation of how SDOH influenced health care use during the years and months immediately preceding the current Covid-19 pandemic; these findings will provide important ‘baseline’ information that can aid future evaluations of the pandemic’s impacts on SDOH and health care use.

Identifying SDOH that Affect Americans’ Health and Health Care Use through ICD-10 Z Codes Utilization

Although two publications have evaluated Z code utilization for Medicare fee-for-service (FFS) enrollees in 2017 (2, 3), there has been little if any research with a national scope that evaluates very recent use of Z codes or Z code use in non-Medicare populations. In 2017, only 1.4% of FFS enrollees had a Z code, and the most common codes were homelessness (Z59.0), problems related to living alone (Z60.2), and disappearance and death of a family member (Z63.4). Among patients with any Z codes, chronic illness incidence was high, and depression incidence was particularly high (4). The current Phase 5 analytic infrastructure now offers an outstanding opportunity to conduct research on recent patterns of Z code assignment and the value of these codes in understanding patients’ health care use.

We expect that SDOH-related social needs are highly underreported in real-world practice, given that 1) the ICD-10 coding architecture and accompanying Z codes were only introduced in 2016, and 2) Z code assignment has generally been voluntary thus far. Nevertheless, we also expect that documented Z codes incrementally add value in characterizing patients’ overall risk profile.

Leveraging our team’s access to very recent health care claims from a large national insurer, this research project will: 1) calculate proportions of claims and patients with SDOH-related Z codes, and identify patient-level predictors of Z code assignment, in national patient populations with Medicare Advantage and commercial insurance coverage; 2) evaluate the extent to which Z codes independently predict subsequent outpatient and inpatient health care utilization, including avoidable inpatient admissions; and 3) attempt to replicate these analyses in Medicaid populations.

Supporting Literature:

  1. Torres JM, Lawlor J, Colvin JD, et al. ICD Social Codes: An Underutilized Resource for Tracking Social Needs. Med Care. 2017;55(9):810-816.
  2. Weeks WB, Cao SY, Lester CM, Weinstein JN, Morden NE. Use of Z-Codes to Record Social Determinants of Health Among Fee-for-service Medicare Beneficiaries in 2017. J Gen Intern Med. 2020;35(3):952-955.
  3. Mathew, J, Hodge, C, and Khau, M. Z Codes Utilization among Medicare Fee-for-Service (FFS) Beneficiaries in 2017. CMS OMH Data Highlight No. 17. Baltimore, MD: CMS Office of Minority Health. 2019.
  4. Mathew J, Hodge C, Khau M. Z Codes Utilization among Medicare Fee-for-Service (FFS) Beneficiaries in 2017. Baltimore, MD2019.

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