The Minimal Important Difference of the Thai Version of the Shoulder Pain and Disability Index and the Bodily Pain Subscale of the Thai Short Form 36 Version 2 Among Patients with Shoulder Pain

Objective: The present study aimed to determine the minimal important difference (MID) of the Thai version of the shoulder pain and disability index (Thai SPADI) and the bodily pain subscale of the thai short form 36 version 2 (Thai SF36v2-BP) among patients with shoulder pain.Material and Methods: A prospective observational study was conducted. Participants with unilateral shoulder pain were assessed using the Thai SPADI and the Thai SF36v2-BP at the baseline and follow-up sessions. Using an anchor-based approach, the MID value was the mean difference in value between the minimal improvement group and the no change group.Results: Of 92 participants, 70 (76%) were diagnosed with myofascial pain, 53 (58%) had pain>6 months. Additionally, the number of participants whose symptoms had undergone deterioration, no change, minimal improvement, and marked improvement were 4, 13, 32, and 43, respectively. The MID (95% confidence interval [CI]) for the total Thai SPADI scale was 10.1 (0.7 to 19.5), while the MID (95% CI) for the Thai SF36v2-BP was 3.1 (-7.2 to 13.5).Conclusion: In patients with shoulder pain, the Thai SPADI had more sensitivity to minimal clinical improvement than the Thai SF36v2-BP.