How Should We Define Clinically Significant Outcome Improvement on the iHOT-12?

There is increased emphasis on efficiently administering patient-reported outcome measures (PROMs). The International Hip Outcome Tool-12 (iHOT-12) is a short-form version of the iHOT-33, and relatively little is known about clinically significant outcomes using the iHOT-12.

The purpose of this study was to define minimal clinically important difference (MCID) and patient acceptable symptomatic state (PASS) for the iHOT-12 and to identify predictors for achieving these psychometric end points in patients undergoing arthroscopic treatment of femoroacetabular impingement (FAI).

Data was prospectively collected and retrospectively analyzed as part of an institutional hip preservation repository. One hundred and twenty patients were included; mean age and body mass index (BMI) were 38.7 years and 25.9, respectively. A majority of patients were female (67.5%) and white (81.7%) and participated in recreational sports (79.2%). The iHOT-12 was administered pre-operatively and at 1-year follow-up to patients undergoing primary hip arthroscopy for FAI. The following anchor question was also asked at 1-year follow-up: "Taking into account all the activities you have during your daily life, your level of pain, and also your functional impairment, do you consider that your current state is satisfactory?" MCID was calculated using a distribution-based method. Receiver-operating characteristic analysis with area under the curve was used to confirm the significance of the PASS threshold.

Mean iHOT-12 scores improved from 35.6 at pre-operative assessment to 70.7 at 1-year follow-up. Patients indicating satisfaction with their outcome improved from 37.5 pre-operatively to 79.0 at 1-year follow-up. MCID value for the iHOT-12 was 13.0. The PASS threshold was 63.0, indicating an excellent predictive value that patients scoring above this threshold were likely to have met an acceptable symptom state. Worker's compensation patients and those with increased BMI were less likely to achieve PASS; lower pre-operative iHOT-12 score was predictive for achieving MCID, and achieving MCID was predictive for achieving PASS.

This is the first study to define PASS and MCID for the iHOT-12, which measures clinically significant outcome improvement comparably to that of other commonly used hip PROMs. As its use becomes more widespread, the iHOT-12 data-points presented in this study can be used to determine clinically significant improvement of patient-reported outcomes.