Responsiveness of specific and generic patient-reported outcome measures in patients with plantar fasciopathy

Purpose: To evaluate and compare responsiveness characteristics for the Foot Function Index revised short form (FFI-RS), RAND-12 Health Status Inventory (RAND-12), and Numeric Rating Scale (NRS), in patients with plantar fasciopathy receiving non-surgical treatment. Materials and methods: This study was conducted on a sub-group of patients from an ongoing randomised controlled trial. One-hundred fifteen patients were included. The patient-reported outcome measures (PROMs) were applied at baseline and after 6 months. Responsiveness was calculated using standardised response mean and area under the receiver operating characteristic (ROC) curve. ROC curves were used to compute the minimal important change (MIC) for the outcome measures. Results: The region specific FFI-RS had best responsiveness and the NRS at rest had lowest responsiveness. Conclusion: FFI-RS were marginally more responsive than the other PROMs. Responsiveness and MIC estimates should be regarded as indicative rather than fixed estimates. IMPLICATIONS FOR REHABILITATION The region-specific Foot Function Index Revised Short Form could, based on responsiveness perspectives, be recommended as an outcome measurement for patients with plantar fasciopathy. Responsiveness and minimal important change estimates are indicative and should be interpreted with caution.