Invited Commentary

Excerpt

The desire to create and validate an instrument that can be used with confidence to conclusively demonstrate the effectiveness of treatment in infants receiving physical therapy is a laudable goal. Palisano et al have shown the merit of a sequential, step-by-step process in establishing the measurement properties of the Peabody Developmental Gross Motor Scale (PDMS-GM) for this purpose. They describe a detailed study in which they answer key questions for evaluative measures: Does the measure show changes in group scores over time? Do most infants show changes in their individual scores? Is the measure responsive to clinically important differences in gross motor skills, and can data from the study be used for sample-size calculations in clinical trials? This article, however, should be making only tentative conclusions for a variety of methodological reasons.