One-year longitudinal test-retest reliability and natural history of grip strength among adults with cerebral palsy

<b>Abstract</b>

<b>Purpose: </b>To assess the one-year longitudinal test-retest reliability of grip
strength (GS) and characterize the natural history of GS among adults with
cerebral palsy (CP).<b></b>

<b>Methods: </b>GS was measured in adults with CP approximately one year apart for
dominant and non-dominant hands using a handheld dynamometer. Test-retest
reliability was estimated with intraclass correlation coefficients (ICC;
two-way mixed-effects, consistency model) for the full cohort and for subgroups
defined by the Gross Motor Function Classification System (GMFCS) and Manual
Ability Classification System (MACS). The natural history of GS was summarized similarly,
including proportions of who increased, maintained, or decreased GS.<b></b>

<b>Results:</b> Fifty-three adults were included (58.5% women; mean [SD] age 37.5 [13.8]
years. ICC (95% CI) was 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
reliability. By GMFCS subgroup, ICCs ranged 0.79–0.91 (dominant) and 0.84–0.93
(non-dominant). By MACS subgroup, ICCs ranged 0.77–0.88 (dominant) and
0.11–0.90 (non-dominant). GS change over one year varied across GMFCS/MACS and
by direction of change.<b></b>

<b>Conclusions: </b>Clinical GS demonstrates good-to-excellent one-year
longitudinal reliability in adults with CP, with lower stability for the
non-dominant hand among individuals with MACS III–V.