Still, the true rate of high blood pressure among U.S. children remains unclear, according to Daniels.
"This new study is narrow in its own way," he said, noting that the kids involved had health insurance and got routine check-ups. The group was racially diverse, but Daniels said they may have been better off -- financially and health-wise -- than a random sample of U.S. kids would be.
The findings, which appear in the February issue of the journal Pediatrics, are based on 199,513 children and teens enrolled in three large health plans.
Almost 11,000 of those kids had an elevated blood pressure reading at their first doctor visit during the study period. But after repeat tests at their next two visits, less than 4 percent of them were ultimately diagnosed with high blood pressure.
All in all, just 0.3 percent of the whole study group had confirmed high blood pressure, the researchers found.
Both Lo and Daniels said the findings underscore the importance of doing repeat measurements to confirm that a child actually has high blood pressure, and not just a temporary spike.
To nail down the true prevalence of high blood pressure, Daniels said researchers need to follow a nationally representative sample of children who have three consecutive blood pressure readings taken over time.
But whatever the true rate is, no one is calling for a change in children's routine care.
High blood pressure may not be highly common in children -- which is "good news," Daniels said. But kids with high blood pressure often become adults with the condition. If not treated properly, high blood pressure can lead to coronary heart disease, heart failure, stroke, kidney failure and other health problems.
"Blood pressure tracks from childhood to adulthood," Lo said. "So diagnosing hypertension in a child suggests it will also be present in adulthood, although this is not 100 percent predictabl
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