Minimal Clinically Important Difference (MCID) of the EOSQ-24 Questionnaire

Orthopaedic management of spinal deformity in patients with early onset scoliosis (EOS) often prioritizes objective radiographic correction; radiographic improvement alone does not fully capture the treatment's meaningful benefits from the patient's perspective. The Early Onset Scoliosis Questionnaire (EOSQ-24) has been previously developed and validated to measure health-related quality of life (HRQoL) in patients with EOS. To date, the traditionally accepted assumption has been that a 10% difference in scores is clinically different. However, an evidence-based estimate for the minimal clinically important difference (MCID) in EOSQ-24 scores is needed.

To determine the MCID for the EOSQ-24 questionnaire and establish a clinically relevant threshold to assess changes in patient HRQoL.

This is a prospective, multicenter study of EOS patients. Eighty-five patients with EOS and/or their parents completed the EOSQ-24 before and after treatment, and the mean change in EOSQ-24 score was calculated. A global assessment survey using a Likert-based scale then evaluated if patients experienced a change (worsening or improvement) after the intervention, and if so, whether it was important to their HRQoL. An anchor-based MCID was determined using a receiver operating characteristic curve to find the threshold score change that optimally identified those with important change. A secondary, 1 standard error of measurement (1 SEM) distribution-based approach was then calculated using the standard deviation of pre-intervention EOSQ-24 scores and a reliability coefficient of 0.92, based on prior validation studies. These 2 methods were compared with determine the MCID.

The mean change in EOSQ-24 score for all patients was 8.5 points (SD = 8.1). The anchor-based MCID was 5.2 with an area under the curve (AUC) of 0.600, indicating a limited discriminative ability of the EOSQ-24 score change. The data distribution-based MCID was 4.6, representing the minimum change to reflect a true difference beyond measurement error.

The final MCID for EOSQ-24 scores in EOS patients is a 5-point change and was derived from 2 methods that were highly consistent, supporting the robustness of this threshold for meaningful change in EOSQ scores. Accurate clinician recognition of important HRQoL changes in this population is important to improve clinical care.

Level II.