Comparing the measurement properties of the ICECAP-A and ICECAP-O instruments in ages 50-70: a cross-sectional study on a representative sample of the Hungarian general population

Objective The ICECAP-A and ICECAP-O were validated as capability wellbeing measures of adults aged 18 + and 65 + years, respectively. We aimed to compare their measurement properties in age group 50-70. Methods Data were derived from a cross-sectional survey among a sample representative for the adult Hungarian population. Respondents aged between 50 and 70 filled in both the ICECAP-A and ICECAP-O questionnaires. We assessed and compared feasibility, agreement, discriminatory power, convergent and content validity of the two instruments and explored the determinants of the differences between the two measures. Results 707 respondents (99.4%) provided full answers to both questionnaires (46.3% women, average age 60.1 years). The instruments showed similar construct and convergent validity and discriminatory power. Pearson-correlations between instrument items were strong (r > 0.5). ICECAP-A and ICECAP-O scores could be calculated from each other with a good confidence (R-2 = 0.69 and 0.71). ICECAP-O scores (mean 0.87, SD = 0.12) were systematically higher than ICECAP-A scores (0.85, SD = 0.15) in most subgroups. The difference increased with the deterioration of capability and health, and with age. Regression results showed that employment and health status had larger marginal effect on the ICECAP-A than on the ICECAP-O scores, and these effects were larger than the effect of age on both measures. Conclusion Validity of both instruments was confirmed in the age groups 50-70. Given that employment and health status are important determinants of the differences between the two instruments besides age, the possibility of linking the choice between ICECAP-A and ICECAP-O to these factors should be investigated by further research.