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How often, when taking an over-the-counter drug, do you read the following note on the label?

“Adults and children 12 years of age and over: one tablet; children under 12 years of age: ask a doctor.”

Pretty often, I guess.

And I’m sure that the fact that children should take drugs differently from adults doesn’t surprise you.

But what is so magic about the age 12 in this particular case? What if the age of your child is 11 and a half years? 11 years and 11 months? Will you “ask a doctor” or take a risk of giving your little one the much-needed relief?

Welcome to the world of pediatrics, a branch of medicine that deals with medical care for children!

Conventional definitions of a “pediatric patient,” a scientific term for a child, bracket the childhood into the age period ranging from the birth to 18 years (although some professional organizations in the United States extend the age limits of pediatrics from fetal life until age 21).

Yet it’s clear that while such a range may make legal sense, it’s too broad to be useful in medical practice. As one report puts it, it’s ridiculous to compare “a 34-week-old premature infant” with “a 17-year-old high school football player.”

To address this problem, more precise age definitions have been introduced, dividing “pediatric patients” into neonates, infants, toddlers, preschoolers, school-agers, and adolescents. However, with so wide variations in individual rates of child development — not to mention cases of physical or mental retardation — placing specific age numbers doesn’t really help.

There is one parameter, though, that seems reasonable, at least for the purposes of dosing drugs: weight. For example, San Mateo, California, County’s medical guidelines define pediatric patients as someone weighting less than 80 pounds. But again, with the spread of childhood obesity reaching epidemic proportions, a child’s weight can be grossly misleading.

We therefore urgently need better predictors of children’s real, biological, age. Let’s call them biomarkers of childhood.

We need to identify and validate a series of biological markers — naturally-occurring molecules collected from easily available body fluids, such as urine and saliva — to follow stages of a child’s physiological and mental development.

These markers will tell us how our child progresses through his or her childhood; these markers will eventually tell us that our child has reached adulthood.

I see at least two areas where biomarkers of childhood can be useful.

First, and the most obvious, is medical care. Although the need for such biomarkers has been long recognized, this area of biomedical research is still in its infancy (no pun intended). This negatively affects both pediatric care as well as child-specific drug development.

But why restrict biomarkers of childhood to medical use? Why not to ask more general questions about the biological differences between children and adults?

What makes your child a child? And although answering this question will require contribution from many different fields, biomarkers of childhood could provide objective and measurable input. I easily see their application in the juvenile justice system, as the most obvious example.

Given the enormous amount of information needed to create a comprehensive list of biomarkers of childhood, it’s clear that this job is well beyond capacity of one single person or even single organization.

The most reasonable venue is to use crowdsourcing that would allow collecting data points from large groups of people around the world.

I therefore call on any party interested in child healthcare and well-being — whether commercial, government, or non-profit — to sponsor a crowdsourcing campaign aimed at creating a comprehensive list of biomarkers of childhood.

I volunteer to work with any non-profit organization to help define specific parameters of such crowdsourcing campaign and to choose an appropriate crowdsourcing platform.