Rating scale, standard gamble, and time trade-off for people with traumatic spinal cord injuries

The rating scale (RS), standard gamble (SG), and time trade-off (TTO) for people with traumatic spinal cord injuries (SCIs) have not been reported. This study compared psychometric performances of these preference-based measures among people with SCIs in Taiwan.

In total, 187 subjects from a nationwide registry of people with traumatic SCIs were interviewed by telephone. Score distributions, interrater reliability, discriminant ability, and convergent validity for the RS, SG, and TTO were compared.

The mean (median) values of the RS, SG, and TTO were 0.67 (0.70), 0.64 (0.75), and 0.53 (0.50), respectively, and their corresponding intraclass correlation coefficients for intrarater and interrater test-retest reliability were .92 and .89, .78 and .73, and .91 and .78. Compared with the SG and TTO, the RS had fewer floor and ceiling values as well as percent changes, more missing observations, a larger effect size, and better discrimination ability. The results of Spearman correlation and factor analysis showed that the SG strongly converged with the TTO (r=.65, and in a single common factor), but they weakly converged with the RS (r=.33 with the SG and r=.27 with the TTO). In the linear regression models, the RS was significantly associated with neurological severity, employment, educational level, and self-care ability; the SG was associated with neurological severity and employment; and the TTO was associated only with neurological severity.

The RS generally performed better than the SG and TTO among people with traumatic SCIs; however, the underlying construct measured by the RS differed considerably from those measured by the SG and TTO.