Comprehending Growth Charts

How well do pediatricians explain growth charts to parents, and how well do those parents comprehend the charts? Not that well, reported pediatric resident Catherine Albert at a recent Hopkins Children’s Grand Rounds.

“I don’t feel parents fully understand the data,” said Albert. “Very few are familiar with terms like BMI (body mass index), which we as pediatricians use very freely. The parents’ interpretation is not always on target.”

Why is that? Many parents, Albert said, may believe they understand enough on the chart to capture the point of it, but often may be off base in their assessments. And some parents, while not fully comprehending the chart, may nonetheless nod their heads in agreement with the pediatrician showing them the chart.

“They don’t want to be embarrassed about not understanding what they’re seeing,” said Albert. “And they don’t ask questions.”

Albert cited an online survey of 1,000 parents, in which 79 percent of the participants said they had seen their child’s growth charts, and that 71 percent of the health-care practitioners had explained the chart to them (Pediatrics, September 2009). But, Albert added, only 56 percent of the parents reported that they understood the data. Also, only 68 percent of the parents were able to accurately interpret the percentile of plotted points for height and weight. The accuracy of interpretation decreased regarding combinations of height-for-age and weight-for-age on the chart.

“Exposure to growth charts is high but comprehension of plotted data is poor,” reported Albert. “Height-weight combinations create more confusion and increase the likelihood of inaccurate assessments by parents. The concept of percentile is often misinterpreted.”

Factors that influenced comprehension of the charts included socio-economic factors like family income, with lower education a stronger predictor than other demographic factors. Previous studies, Albert said, have shown that literacy is an important variable in understanding growth charts.

What can pediatricians do?

Show growth charts at every visit, suggests Albert, and ask questions to assess parents’ understanding. Studies have shown, she added, that repetition improves interpretation.

“Pediatricians can use growth charts more frequently, ideally with every well-child visit,” said Albert. “The value of a growth chart is more than just exposure. The key is getting the parents to use the data to assess their child’s growth.”