Establishing Minimum Clinically Important Difference Thresholds for Physical Function and Pain in Patients Undergoing Anterior Lumbar Interbody Fusion.

OBJECTIVE

To establish minimum clinically important difference (MCID) in anterior lumbar interbody fusion (ALIF) for the physical function patient-reported outcome measures, Patient-Reported Outcomes Measurement Information System Physical Function (PROMIS-PF), 12-Item Short Form (SF-12) physical component score (PCS), Veterans RAND 12 (VR-12) PCS, and pain patient-reported outcome measures visual analog scale (VAS) back and VAS leg through anchor- and distribution-based calculations.

METHODS

Patients undergoing ALIF with preoperative and 6-month Oswestry Disability Index were included. Using Oswestry Disability Index as the anchor, anchor-based calculation methods were the average change, minimum detectable change, and receiver operating characteristic curve methods. Distribution-based methods were the standard error of measurement, reliable change index, effect size, and half of the standard deviation (0.5ΔSD).

RESULTS

Fifty-one patients were identified. Anchor-based methods ranged from 2.9 to 11.5 for PROMIS-PF, 8.2-13.6 for SF-12 PCS, 7.8-16.8 for VR-12 PCS, 0.5-3.9 for VAS back, and 1.0-3.4 for VAS leg. The area under curve ranged from 0.59 (VAS back) to 0.78 (VR-12 PCS). Distribution-based methods ranged from 1.0 to 4.2 for PROMIS-PF, 1.8-12.2 for SF-12 PCS, 1.9-6.2 for VR-12 PCS, 0.4-1.6 for VAS back, and 0.5-1.7 for VAS leg.

CONCLUSIONS

The MCID values greatly relied on the calculation method. The minimum detectable change method was selected as the most appropriate MCID calculation method. The MCID values that may be utilized for ALIF patients are 7.3 for PROMIS-PF, 8.2 for SF-12 PCS, 7.8 for VR-12 PCS, 3.2 for VAS back, and 2.2 for VAS leg.