Reliability and validity of the ACTIVE-mini for quantifying movement in infants with spinal muscular atrophy

Background: Motor function assessment of individuals with SMA I is challenging due to the low level of function typically obtained and the fragility of the infant. Outcome measures currently used by clinical evaluators, such as the CHOP INTEND, require significant training due to their subjective nature and can be fatiguing to the infant. Outcome measures that can objectively distinguish small changes over time without adding significant stress on the infant with SMA Type I are needed to determine the effectiveness of intervention and change over time. The purposes of this study were to investigate the reliability and validity of the ACTIVE-mini for quantifying movement in infants with SMA, specifically, within-day test-retest reliability, between-day test-retest reliability, convergent validity, and construct validity using the known-groups method. Methods: This study was a cross-sectional, repeated measure design with two groups. Non-rolling infants with SMA and function-matched non-rolling typically developing infants. The dependent variables included a CHOP INTEND extremity score and a predicted CHOP INTEND extremity score determined by data captured with the ACTIVE-mini. Dependent variables were collected at two time points in a standardized order with standardized assessment. An ICC was calculated to determine within day test-retest reliability and between day test-retest reliability. To examine the convergent validity of the ACTIVE-mini, a Pearson correlation was used to analyze the relationship between the predicted CHOP INTEND score and the observed CHOP INTEND extremity score. An independent sample t test was run to examine the construct validity of the ACTIVE-mini using the known groups method. Results: There was good reliability for both within day and between day test-retest reliability of the ACTIVE-mini derived score in subjects with SMA. There was a moderate positive correlation of the ACTIVE-mini score with the observed CHOP INTEND extremity score. There was a statistically significant difference of the predicted CHOP INTEND score between the function-matched controls and subjects with SMA. Conclusion: The results of this study support the use of the ACTIVE-mini for quantifying movement in infants with SMA. There was good test-retest reliability of the tool as well as good convergent and construct validity. The ACTIVE-mini can be used in conjunction with physiologic biomarkers and clinical assessments to offer a more complete report of overall status of the child with SMA I. It may also offer information regarding function over a period of time or at multiple time points that could not be completed with one single clinical assessment. It can be completed in various settings, is quick to administer, and is not burdensome to the infant and it’s family. While the CHOP INTEND will continue to be the gold standard for measurement of function in infants with SMA, the ACTIVE-mini may be a useful tool that could help resolve the issues of the CHOP INTEND such as fatigue with testing and subjectivity of scoring. Use of the ACTIVE-mini system may aid in understanding disease progression and response to therapeutic agents and interventions in multisite clinical trials and for clinical assessment in patients with SMA I.