Responsiveness and Minimal Clinically Important Difference of the Thai Version of the International Knee Documentation Committee Subjective Knee Form in Patients With Anterior Cruciate Ligament Injury.

BACKGROUND

The International Knee Documentation Committee Subjective Knee Form (IKDC-SKF) is a knee-specific patient-reported outcome (PRO) measure that is commonly used to evaluate patients with various knee disorders. The Thai version of the IKDC-SKF (Thai IKDC-SKF) was shown to have good validity and reliability; nonetheless, no data regarding its responsiveness are available.

PURPOSE: To evaluate the responsiveness of the Thai IKDC-SKF for assessing patients with anterior cruciate ligament (ACL) injury and determine the minimal clinically important difference (MCID) for this PRO measure.

STUDY

DESIGN

Cohort study (diagnosis); Level of evidence, 3.

METHODS

This prospective study included ACL-injured patients who were scheduled for ACL reconstruction (ACLR) at a single institution. The patients completed the Thai IKDC-SKF at the baseline and the 6-month postoperative follow-up. The global rating of change scale was an anchor question that evaluated patients' overall perception of a clinical change compared with their preoperative condition. The effect size and standardized response mean were calculated. The MCID was identified with an anchor-based approach by plotting a receiver operating characteristic curve and calculating the value that maximized the Youden index.

RESULTS

Of 59 enrolled patients, 53 patients (89.8%) completed the preoperative and 6-month postoperative Thai IKDC-SKF. The mean (±SD) age of the participants was 32.3 ± 10.3 years, and 86.8% were men. The mean Thai IKDC-SKF score improved significantly from preoperatively to the 6-month follow-up (from 56.3 ± 14.9 to 70.8 ± 14.1, respectively; P < .001), with an effect size of 0.975 and a standardized response mean of 0.977. A receiver operating characteristic curve was generated to determine the ability of the Thai IKDC-SKF to distinguish between improved patients and unimproved patients, and the area under the curve was 0.80 (95% CI, 0.68-0.92), which was considered excellent. The MCID was 15.5, which yielded a sensitivity and specificity of 0.55 and 1, respectively.

CONCLUSION

This study confirmed the responsiveness of the Thai IKDC-SKF for detecting a clinical change in ACL-injured patients after ACLR. The identified MCID of 15.5 can be used to calculate the significant clinical change and sample size in future studies.