400 Section - 1-year Longitudinal Test-Retest Reliability and Natural History of Grip Strength in Adults with Cerebral Paly

To assess the one-year longitudinal test-retest reliability and natural history of grip strength (GS) among adolescents and adults (≥16 years old) with cerebral palsy (CP).

Design:

A convenience-based subset of participants from a previous cross-sectional study (05/2021–12/2021) were invited for a one-year follow-up to characterize GS reliability and natural history. GS was measured for both dominant and non-dominant hands using a Jamar Hydraulic Hand Dynamometer. Test-retest reliability was estimated by intraclass correlation coefficient (ICC) using a 2-way mixed-effects consistency model for the entire cohort (n=53) and subgroups defined by the Gross Motor Function Classification System (GMFCS) and the Manual Ability Classification System (MACS). The natural history of GS was analyzed using group-level and individual-level statistics, including patterns of increase, stability, or decrease over one year.

Results:

The cohort (mean age 37.5 years; 58.5% women) had ICCs (95% CI) of 0.92 (0.86–0.95) for the dominant hand and 0.91 (0.85–0.95) for the non-dominant hand, indicating good-to-excellent longitudinal reliability. For GMFCS subgroups, ICCs ranged from 0.79–0.91 (dominant hand) and 0.84–0.93 (non-dominant hand). For MACS subgroups, ICCs ranged from 0.77–0.88 (dominant hand) and 0.11–0.90 (non-dominant hand). The natural history of GS showed individual variation, with participants exhibiting either increases, stability, or decreases in GS, reported by GMFCS and MACS classifications.

Conclusion:

GS measured in the clinical setting shows good-to-excellent reliability over one year in individuals aged ≥16 with CP. Most GMFCS and MACS subgroups demonstrated consistent longitudinal reliability, except for the non-dominant hand in MACS III-V, supporting the use of GS as a reliable clinical measure and indicator of natural history in CP.