Minimal Important Difference (MID) of two commonly used outcome measures for foot problems

Area of Science:

• Orthopedics
• Pain Management
• Clinical Measurement

Background:

• The Visual Analogue Scale (VAS) and Foot Health Status Questionnaire (FHSQ) are standard tools for assessing foot health outcomes.
• Establishing the Minimal Important Difference (MID) is crucial for interpreting the clinical significance of changes measured by these instruments.

Purpose of the Study:

• To calculate the Minimal Important Difference (MID) for the VAS and FHSQ in individuals experiencing plantar heel pain.
• To provide evidence-based values for clinicians and researchers to better understand meaningful improvements in foot health.

Main Methods:

• An anchor-based method was employed using data from 184 participants in two randomized trials for plantar heel pain.
• The MID was calculated for average pain and first-step pain using the VAS (100 mm scale).
• The MID was determined for the foot pain, foot function, footwear, and general foot health domains of the FHSQ.

Main Results:

• The MID for VAS average pain was -8 mm and for first-step pain was -19 mm.
• For the FHSQ, the MID was 13 points for pain and 7 points for function.
• The MID for the FHSQ footwear domain was -2 points, and for general foot health was 0 points.

Conclusions:

• The calculated MIDs for the VAS and FHSQ provide valuable benchmarks for assessing treatment effectiveness in plantar heel pain.
• These MIDs enhance the interpretation of patient-reported outcomes, signifying a minimal, worthwhile change.
• The findings will aid researchers in designing future studies and performing accurate sample size calculations.