This study aimed to determine the validity and reliability of the Spanish version of the iHOT-12 (iHOT-Sv) to assess physical function and health-related quality of life in a population of young patients with femoroacetabular impingement with or without labral tear. Based on our results, the iHOT-12-Sv could be successfully recommended in physically active and young Spanish-speaking patients with hip conditions.
The internal consistency of the iHOT-Sv was excellent, demonstrating that all items contributed to the scale. These results are reinforced by previous validation studies [8, 10, 12], obtaining in most of them a Cronbach's alpha > 0.90 (e.g., the French version obtained a Cronbach’s alpha = 0.86) [11], but without obtaining a value high enough to reflect the presence of redundant items. Internal consistency is an important aspect to determine the homogeneity among the items on a test for verifying whether the items are consistent with each other measuring the same thing [32]. In addition, according to EFA findings, the final version of the iHOT-Sv consisted of 12 items englobed into one of the original factors, resulting in a reasonably good model and obtaining an optimal factor loading (≥ .641). Hence, the iHOT-12-Sv presented a unifactorial model, in line with the originally created version of the scale and with previous validations to other languages [7–12]. On the other hand, in line with previous validations of the iHOT-12 scale [8, 12], our results showed no floor or ceiling effects. Therefore, this version shows an adequate discriminant capacity and could be used for measuring changes on physical function and quality of life in young and active patients with hip pathology.
Convergent validity was evaluated with the HOS and the iHOT-33 as are applicable for assessing outcomes of treatment interventions in this patient population and previously validated in the Spanish language [13, 31]. The iHOT-12-Sv demonstrated strong correlations with the HOS and a very strong correlation with the iHOT-33. Thus, both subscales of the HOS analyzed independently showed strong correlations. Therefore, this iHOT-12-Sv could be considered a valid, short and simple alternative to the full version for its use in prospective clinical research.
The iHOT-12Sv demonstrated excellent test-retest reliability. Our reliability estimates (ICC = 0.93) were comparable to the French (0.84), Swedish (0.88), English (0.89), Turkish (0.92), Dutch (0.93) and German (0.94) versions of the iHOT-12 [7, 8, 10–12]. No systematic bias was found between the first and the second attempts. In addition, the MDC was similar to those obtained in previous validations of the scale [8, 10–12]. Specifically, according to our results, a change in the iHOT-12-Sv score equal to or greater than 17.21 points would indicate that it is a real change and not due to measurement error. It is important to mention that all the items of the iHOT-12 are included in the iHOT-33 [4]. Thus, although they are not totally comparable, it could be considered that the Spanish version of 12 items is somewhat less sensitive to change than the extended version of 33 items, since the latter presents an MDC of 12.5 points. Logically, this difference could be attributed to the greater precision obtained by increasing the number of items. However, we consider that the slight increase in sensitivity to change does not compensate for the greater time invested in completing the extended version. Based on the above, we consider that the iHOT-33 could be a more interesting scale to apply in the research setting, whereas the application of the iHOT-12 in the clinical setting could be more relevant and more widely accepted.
Limitations
Some limitations of this study must be acknowledged. Firstly, this study used a convenience sample, which could affect the extrapolation of the results to other hip disorders. Another limitation is that the Spanish language used in Spain differs from the Spanish used in other Spanish-speaking countries, so it is unknown whether the metric properties of the scale would be maintained when applied in other Spanish-speaking countries due to linguistic and cultural differences. Finally, the degree of improvement or change perceived by the patients (subjective assessment) was not assessed, so the minimum clinically important difference could not be determined.