Association of Z-codes and Mortality in Patients with AKI and Heart Failure

Background: Acute kidney injury (AKI) is a serious complication in patients admitted for acute decompensated heart failure (ADHF). Z-codes are part of the ICD-10-CM coding system codes for social determinants health (SDOH). There is a lack of data regarding the association of coding for SDOH on outcomes in patients admitted for ADHF. Methods: This was a retrospective study using the National Inpatient Sample to identify patients admitted for ADHF and diagnosed with AKI from 2016 to 2020. Patients who had ESKD were excluded. The primary outcome was in-hospital all-cause mortality. Patients with Z-codes were compared to propensity matched patients without Z-codes. To determine if having Z-codes modifies the odds of requiring dialysis by race, we included an interaction term of Race x having any Z-code. Results: There were 481,298 patients admitted for ADHF and diagnosed with AKI during their hospital stay. 4,650 patients with Z-codes were propensity matched with 4,650 patients without Z- codes. Compared to the control group, those who had Z-codes are associated with signficantly lower odds of mortality (OR: 0.96 CI:0.96 -0.97). Females (OR 0.54; CI: 0.50- 0.578) and older (OR 0.96; CI: 0.96 - 0.96) individuals were significantly less likely to have any Z-codes. Compared to Whites, Black (OR 1.53; CI: 1.41 - 1.66), Hispanic (OR 1.14; CI:1.01 - 1.23) and Asian (OR 1.35 ; CI: 1.06-1.73) patients were significantly more likely to have Z-codes. Z-Code is associated with a significantly decrease odds of dialysis (OR: 0.52; CI: 0.36 – 0.76). Compared to Whites those who are Hispanic (OR:1.21; CI: 1.11- 1.31) and Asians (OR 1.32; CI:1.15 - 1.51) are significantly more likely to end up on dialysis during their hospital stay. However, there is no significant association for odds of requiring dialysis when comparing Whites with Z-Codes and Blacks (p=0.72) and Hispanics (p=0.61) with Z-Codes. Conclusion: We found that in matched cohorts, the presence of a Z-code lead to lower odds of mortality. Black, Hispanic, and Asian individuals were significantly more likely to have Z-codes than White individuals. These results maybe due to provider recognition and documentation of unmet SDOH, noting the importance of unmet SDOH.