Clinimetric Properties and Minimal Clinically Important Differences for a Battery of Gait, Balance, and Cognitive Examinations for the Tap Test in Idiopathic Normal Pressure Hydrocephalus

BACKGROUND Idiopathic normal pressure hydrocephalus (iNPH) is treated by insertion of a ventricular peritoneal (VP) shunt. To help identify who would benefit from a VP shunt, patients undergo a tap test (TT). Several measures can identify change from a TT, but the magnitude of change and the combination of measures that indicate the improvement from a TT is unclear. OBJECTIVE To develop minimal clinically important differences (MCIDs) for a battery of gait, balance, and cognitive measures in relation to improvement from the TT, and to identify which combination of measures best identifies when improvement has occurred. METHODS Observational study of iNPH patients undergoing a TT for consideration of a VP shunt. Patients completed the: The Timed Up and Go (TUG), Timed Up and Go cognition (TUG-C), Performance Oriented Mobility Assessment (Tinetti), and Berg Balance Scale (BBS) pre- and post-TT. A Global Rating of Change scale assessed patients' perceived improvements in gait and balance post-TT. RESULTS MCIDs for the TT were (calculated as percentage changes): TUG: 13%, TUG-C: 11% Tinetti: 36%, and BBS: 20%. A combination of the TUG-C and Tinetti resulted in sensitivity of 90.28% to identify improvement, while the Tinetti and BBS resulted in specificity of 98.58% to exclude improvement from a TT. CONCLUSION These MCIDs provide the first evidence to quantify the significance of post-TT symptom changes and provides objective data to guide recommendations for clinical management. Utilizing a combination of measures, and these MCIDs as cut off values, results in high sensitivity and specificity for identifying improvement from a TT.