||Wang, Q., El-Dassouki, N., Edwards, N., Mutia, P., Khairalla, R., Yanga, N., Saqib, M., Ali, A., Ford, H., Dychiao, A., Mucsi, I.
||Purpose: This study validates the 2016 Ontario Marginalization Index (OMI) scores derived from 3-digit postal codes to enable its research use in place of scores derived from 6-digit postal codes which may be difficult to use in research due to privacy concerns.
Methods: A cross-sectional sample of adults with end-stage kidney disease (ESKD) in Toronto completed standard, validated questionnaires. Socio-economic status (SES) was assessed by patient-reported information on neighborhood safety (NS), number of permanent household residents (HR), annual household income (HI), vehicle ownership (VO), employment, ethnicity, and immigration. OMI scores were generated by linking the first 3 digits of postal codes using the Statistics Canada Postal Code Conversion File. OMI quintile scores were calculated from population weighted average factor scores. Each quintile represents 1/5th of the geographic units in the Greater Toronto Area, ranked from Q1-Q5 (least-most marginalized).
Results: Of the 1163 participants (mean [SD] age = 56  years), 61% were male, 50% were White, 58% had ≥12 years education, 38% received transplant. For OMI Residential Instability (ORI), the proportion of patients with low NS across Q1-Q5 was 10, 6, 15, 17, and 12% (p=0.02); the proportion of patients with <3 HR across Q1-Q5 was 37, 45, 53, 63, and 73% (p<0.001). For OMI Material Deprivation (OMD), the proportion of patients with HI <$30,000 across Q1-Q5 was 22, 28, 20, 38, and 61% (p<0.001); the proportion of patients without VO across Q1-Q5 was 22, 12, 12, 17, and 41% (p<0.001). For OMI Dependency (OD), the proportion of unemployed patients across Q1-Q5 was 53, 64, 73, 60, and 67% (p<0.001). For OMI Ethnic Concentration (OEC), the proportion of non-White patients across Q1-Q5 was 20, 19, 43, 60, and 74% (p<0.001); the proportion of immigrant patients across Q1-Q5 was 20, 30, 47, 62, and 71% (p<0.001).
Conclusion: This study showed that OMD, OD, and OEC scores were significantly associated with the hypothesized trends of several corresponding patient-reported SES measures, whereas the ORI score was inversely associated with hypothesized trends. As such, we propose that OMD, OD, and OEC scores derived from 3-digit postal code are appropriate measures of SES and can be used to assess SES in studies enrolling patients with end stage kidney disease. The ORI score requires further study before being used.