The pilot study, which is part of a larger longitudinal study designed to monitor the growth of children with SMA, contains a procedural manual with clear guidelines on evaluating children’s nutrition and body composition. The manual is now available for the scientific and medical community.
SMA is a genetic neurodegenerative disorder caused by the gradual loss of motor neurons — the nerve cells responsible for controlling voluntary muscles — in the spinal cord, leading to muscle weakness. SMA is also associated with feeding disorders, alterations in energy metabolism, nutritional status impairments, and changes in body composition.
“Body composition assessment is paramount to the assessment of nutritional status, and, despite the challenges that it poses, anthropometry [human physical measurements] is still the most widely used method in the clinical setting,” the researchers wrote.
However, standardized measurements especially adapted for SMA patients have never been developed, due to the rarity of the disorder.
To this end, the researchers in this study described and implemented a new standard method to assess the nutritional status of children with SMA.
First, the team created a procedural manual for anthropometric measurements. This manual provided the basis for a two-day workshop intended to train five observers who would then perform the measurements on the study participants.
During the first day, observers learned and practiced the techniques of the procedural manual from the lead anthropometrist and, on the second day, used them to collect a complete set of measurements in children with SMA.
All procedures included in the manual took into consideration not only body composition and growth, but also physical limitations associated with SMA, including reduced muscle mass and tone, muscle contractions, inability to stand, scoliosis, and other bone deformities.
The accuracy of the method was determined by a coefficient of reliability (R) between each observer and the lead anthropometrist. If observers lacked accuracy (R values were lower than 0.9), they were scheduled for retraining. Inter-observer reliability was assessed by a technical error of measurement (TEM), relative TEM (%TEM), and R values.
The pilot study involved six children — three with SMA type 2 and three healthy controls — between the ages of 2 and 7. After the two-day workshop, two observers were accurate at performing measurements (R values of 0.932 and 0.915), while another two required additional training (R values of 0.837 and 0.789).
Regarding anthropometric measurements, arm length had low reliability values across all measurements (R value of 0.830). For circumference measurements, the TEMs were lower than 1 cm, and reliability values were all above 0.9 (accurate), with the exception of arm circumference.
For skinfold thickness, reliability values were again all accurate (R above 0.9), with the exception of those concerning the biceps (R of 0.721). No difference was found in measurement reliability between healthy and SMA children.
“The assessment of nutritional status in SMA patients is currently a topic of interest to evaluate the effects of new therapies on body composition and its role in improving motor function. Anthropometry can be a useful tool for large multicenter studies, but gold standard methods … will also be needed to validate reference and field methods in SMA,” the investigators wrote.
“Careful consideration of every aspect of the data-collection process should lead the operator to avoid common sources of measurement error and this standardization process could be a useful tool for multicenter studies aiming to fill the gaps in the knowledge of nutritional status of SMA,” they concluded.