Role of the Functional Gait Assessment in Validating Item Difficulty Hierarchy and Fall Risk for Idiopathic Normal...

Falls along with gait-balance disturbances are important symptoms of idiopathic normal pressure hydrocephalus (iNPH).

This study aimed to validate the Functional Gait Assessment (FGA) item-difficulty hierarchy, determine its optimal fall cutoff value, and identify key items for assessing fall risk in iNPH.

One hundred eighty-eight iNPH patients underwent pre-intervention assessments using the FGA, timed up-and-go (TUG), 10-Meter Gait Speed (10MGS) tests, and their falls history in the past 6 months. Rasch analysis confirmed the validity of the FGA item-difficulty hierarchy and established the relationship between total scores and logit estimates. Logistic regression identified the optimal FGA cutoff value and key fall-related items.

The FGA's item-difficulty hierarchy was confirmed to range from item 5 ("gait and pivot turn") at -2.58 logits (easiest) to item 7 ("gait with narrow base of support") at 5.35 logits (most difficult). Total scores corresponded to logits from -10.39 (score 0) to 11.64 (score 30). The fall rate was 63.3%. The optimal FGA cutoff value was ≤15 points (area under curve [AUC]: 0.901, P < 0.001), outperforming TUG (AUC: 0.712) and 10MGS (AUC: 0.742). Key fall-related items (R²: 0.545, P < 0.001) were item 2 ("change in gait speed"), item 7 ("gait with narrow base of support"), item 1 ("gait on level surface"), item 10 ("stair steps"), and item 5 ("gait and pivot turn").

Our findings may facilitate early diagnosis and timely interventions, including tailored rehabilitation and fall prevention strategies, by leveraging the item difficulty and characteristics of the FGA for iNPH patients.