External validity of the Both Hands Assessment for evaluating bimanual performance in children with bilateral cerebral palsy.

Aim: To investigate the external validity of the Both Hands Assessment (BoHA), a new test evaluating bimanual performance in children with bilateral cerebral palsy (CP), by analysing its relationship to established measurements of hand function and self-care skills.

Method: In this cross-sectional study, we recruited children with bilateral CP and manual ability corresponding to Manual Ability Classification System (MACS) levels I to III attending three habilitation units in Norway. All participants completed the BoHA. Unimanual capacity was assessed using the Bimanual Fine Motor Function (BFMF) classification, the Box and Block Test (BBT), and the Melbourne Assessment 2 (MA2). Self-care skills were assessed with the Pediatric Evaluation of Disability Inventory (PEDI).

Results: Thirty-nine children (19 males, 20 females; mean age 8y 2mo, SD 2y 8mo; age range 2y 8mo-12y 6mo) were included. Spearman's correlation coefficient (ρ) suggested high correlation between the BoHA and MACS (p=0.89; 95% confidence interval [CI]  0.79-0.94), BFMF classification (p=0.84; 95% CI  0.71-0.91), and BBT for the non-dominant (p=0.85; 95% CI  0.68-0.95) and dominant hand (p=0.72; 95% CI  0.53-0.85). The Spearman's ρ between the BoHA and the MA2 subscales varied between 0.48 and 0.83, while the PEDI's ρ was 0.51 (95% CI  0.33-0.67).

Interpretation: The BoHA provides valid measures of hand use as suggested by its high correlation with other activity-based measures of hand function.