How real is the crisis of undiagnosed high blood pressure in children?

Worrisome news hit parents this week that more than a million children have high blood pressure that’s not being diagnosed by their pediatricians. Childhood obesity was blamed for growing numbers of children with elevated blood pressures. Before parents become alarmed that their pediatricians aren’t caring for their children properly, or that they need to put their kids on weight loss plans to prevent them from having organ damage, strokes and heart attacks, they’ll want to learn a few things about this study that the news hasn’t reported.

There are a few key questions to ask: How was blood pressure measured, how was “high” blood pressure defined and how was a “diagnosis” of high blood pressure determined?

First the news....

The Associated Press reported:

Many kids' high blood pressure undiagnosed

More than 1 million U.S. youngsters have undiagnosed high blood pressure, putting them at risk for developing organ damage down the road, a study suggests. Calculating elevated blood pressure in children is trickier than in adults, and many doctors may not bother evaluating kids' numbers because they assume that hypertension is an adult problem.

But the study shows that many children are affected, too, said lead author Dr. David Kaelber of Case Western Reserve University in Cleveland and Harvard Medical School. Roughly 2 million U.S. youngsters have been estimated to have high blood pressure; the study suggests that three-quarters of them have it but don't know it. The numbers are driven at least partly by rising rates of obesity, which is strongly linked with high blood pressure....

The researchers analyzed medical records for 14,187 healthy children aged 3 to 18 who had at least three checkups in northeast Ohio between June 1999 and last September... The researchers calculated that 507 study children had high blood pressure, or 3.6 percent, which is within estimates for the nationwide prevalence of high blood pressure in children. But only 131 of them, or 26 percent, had a documented high blood pressure diagnosis....

The Telegraph, like most television news, added fears about obesity:

The obesity epidemic is causing an increase in the number of children with high blood pressure, doctors have warned. New research has shown that the problems with obesity is causing conditions previously only seen in adults to be diagnosed in children....The team warned that doctors need to be more aware of the condition.

Listening to the news, most parents probably came away thinking that blood pressures have been rising in children and teens — when, in fact, there is no evidence that they have risen in decades (due to obesity or anything else). Many parents this week understandably thought that it must be important to watch their children’s blood pressures to protect them from heart disease and organ damage. Few heard that this is controversial in the medical community, nor did they hear of the uncertainties of blood pressure readings in growing children. Instead, parents heard frightening quotes like the one from Dr. Reginald Washington, a member of the American Academy of Pediatrics obesity task force, who said: “We can't wait until they've had a stroke to figure this is a problem.”

As has been extensively reviewed, there is no epidemic of heart attacks and strokes among kids, nor has any clinical research shown that kids’ blood pressure measurements identify those at risk of later developing heart disease or that treating their blood pressures decreases the incidence of cardiovascular disease in adulthood. The U.S. Preventive Services Task Force, after reviewing all available clinical evidence, recently concluded that the evidence is insufficient to recommend routine screening for high blood pressure in children and adolescents to reduce their risks for cardiovascular disease.

Despite the media’s focus on the dangers of high blood pressure in children, this new study did not find a single child who had been harmed by their blood pressures. It didn’t examine a single child at all.

This is another example of the need to look carefully at exactly what is being reported. I highlighted three phrases in the Associated Press story — medical records, calculated, documented — as clues. Let’s look at their meaning more carefully.

"Medical records"

The authors of this latest journal article culled through an electronic database of medical records on 14,187 children — not all children, just those in a Ohio health plan whose pediatricians’ offices had taken three blood pressure readings during well child visits and recorded them electronically. The blood pressures had been recorded during routine clinical care, using automated equipment. The significance of this bit of information will be recognized by Junkfood Science readers. [For those who missed it, blood pressure readings in children were covered extensively here.] Not only are 74% of blood pressures taken by clinical staff, especially using automated equipment, inaccurately high (by about 13.2 mmHg systolic and 9.6 mmHg diastolic), but larger children are most likely to have incorrect high readings. Offices routinely don’t control for appropriate cuff sizes, technique and equipment calibration, activity levels, excitement/anxiety, pain, asthma, or fevers in children when their check-in blood pressures are taken, for example.

The authors admitted: “We had no way to independently assess the accuracy of the blood pressure measurements in the electronic medical records or the degree to which the blood pressure procedures were followed.”

"Calculate"

Then, to calculate the children they believed had high blood pressure, they arbitrarily labeled every child at or higher than the 95th percentile for age, sex and height as having “high” blood pressure. Children at or higher than an arbitrary 90th percentile cut-off were deemed to have “prehypertension.”

Of course, well-established facts are that blood pressures rapidly increase during growth and maturation and kids and teens are growing quickly and are varying stages of growth and development at any particular age and size. The idea that fat children whose blood pressure measurements naturally fall a few mmHgs over arbitrary limits for their age are in danger and in need of intervention to prevent heart disease is being popularized by vested interests, but unsupported by the evidence.

The tables being promoted by the authors of this study are from the Fourth Report on the Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents and are far more controversial and arbitrary than most parents, and clearly the media, realize. For example, there is a difference of one mmHg between the 90th and 95th percentile for systolic blood pressures among boys at every age. And the definitions for normal blood pressure, increases at each year of age by a mere one or two mmHg, leaving little room for error. The tiniest error in a blood pressure reading can tip a child into being misdiagnosed as “hypertensive” yet, as we’ve seen, blood pressure readings taken at most offices vary by considerably more than that.

"Documented"

The authors of this study defined the children who were “diagnosed” with hypertension as being that same as those checked off as “hypertensive” on ICD-9 codes. These codes (from the International Classification of Diseases, Ninth Revision) give a number to some 12,000 conditions and are used on billing claim forms by insurance companies for reimbursement purposes. Their inaccuracies in reflecting actual patient conditions is well documented. In today’s pay-for-performance, labeling a child as hypertensive also comes with a slew of mandated tests and interventions. The Fourth Report recommends extensive testing, lifestyle interventions (beginning with weight reduction), treatments and medications for children labeled as hypertensive.

The fact that a pediatrician doesn’t believe a growing child or teen whose blood pressure reading is a few points “high” on a standardized chart is diseased or benefitted by being labeled as “hypertensive” could be seen as sound medical judgment. As the U.S. Preventive Services Task Force latest review of the evidence noted, the evidence is most supportive of the merits of treating extremely high levels, not lesser numbers, and it found no evidence to support increasingly more aggressive blood pressure management goals.

Not putting “hypertensive” on a billing claim form is not the same thing as a pediatrician failing to recognize, treat or care for children with true high blood pressures. [See the recent review of hypertension in children for the medical issues doctors do watch for.]

The authors of this study said: “This low diagnosis rate could be accounted for by two primary factors: (1) lack of knowledge of normal blood pressure ranges and (2) lack of awareness of a patient's previous blood pressure readings...clinicians typically cannot remember normal blood pressures for the wide range of children observed in the typical primary care setting.” Besides being insulting to medical professionals, for whom blood pressure is a notable part of their medical training, pediatricians are quite capable of remembering normal values or how to look at a table if they “cannot remember.” Pediatricians who aren’t monitoring the blood pressures among healthy children aren’t doing so because they can’t be bothered, as the Associated Press suggested, but more likely because they have kept abreast of the medical research.

The authors concluded: “[I]n well-child care visits, clinicians should be focused on screening and prevention of diseases including hypertension.” They provided no new clinical evidence for this “should,” however, and it is inherent upon them provide it since, as the U.S. Preventive Services Task Force found, currently, the evidence is insufficient to recommend routine screening for high blood pressure in children and adolescents to reduce their risks for cardiovascular disease.

Nor is there any grounds for millions of parents to fear for their children or that pediatricians are putting their children in danger.

© 2007 Sandy Szwarc