Individual patient monitoring in daily clinical practice: a critical evaluation of minimal important change.

Purpose: In daily practice, physicians translate knowledge from clinical trials to practice, to improve health in individual patients. To help interpret meaningful change on disease outcome measures, the concept of minimal important change (MIC) was conceived. The objective of this study was to investigate whether MIC values are suited for individual patient monitoring.

Methods: Three main elements of the MIC concept were evaluated: (1) MIC values for improvement and deterioration were determined, and the amount of misclassification present in quantifying minimal change was analyzed. (2) Discordance between change categories (improved, unchanged, deteriorated), defined by the MIC values, and patients' satisfaction with their health was inspected. (3) Discordance between change categories, defined by MIC values, and patients' willingness to alter therapy was inspected.

Results: MIC value analysis was based on 469 patients with RA seen in daily practice. The chance of falsely classifying health change of an individual patient was high (false-positive range 19-30 % and false-negative range 43-72 %). Of patients classified as improved, 24 % were not satisfied with their health and 69 % were not willing to change therapy. Of patients classified as deteriorated, 54 % were satisfied with their health and 57 % were not willing to change therapy.

Conclusions: The misclassification in the quantification of change and high proportions of discordance between change categories defined by MIC cutoff values and patients' satisfaction and willingness to alter therapy indicate that MIC values as such are not suited for individual patient monitoring.