Advisers Say National Children's Study Should Represent U.S. Population

25 April 2012 5:25 pm

An advisory committee that met yesterday to consider the design of the struggling National Children's Study (NCS) came down firmly in favor of one option: The study should recruit children from a geographic sample that represents the entire U.S. population. But whether the National Institutes of Health (NIH) will go with that plan isn't yet clear.

Proposed by Congress 12 years ago, NCS aims to enroll 100,000 pregnant women and follow their babies' health from before birth to age 21. In February, NIH announced that because the original plan to recruit women from certain addresses in 105 counties was too expensive, it was revising the design to cut 15% from the NCS's $193 billion budget. Instead of recruiting women from a probabilistic sample of the U.S. population, NIH said it might instead find women through doctors participating in health care plans, a so-called convenience sample of providers.

This proposal drew concern from many researchers and questions from Congress. Those who have run pilot studies at 40 "vanguard" centers that have enrolled thousands of women were also alarmed to learn that some sites would soon be transferred to a new contractor.

At yesterday's meeting of the advisory committee and ad hoc advisers in Bethesda, Maryland, Alan Guttmacher, director of the National Institute of Child Health and Human Development (NICHD), which oversees the study, said that NIH was looking for "an exploration by thoughtful, informed folks" of various sampling strategies. NCS Director Steven Hirschfeld later clarified that the role of the 105 counties had not yet been decided: "We don't know yet what locations will be in the sampling frame or not."

During the daylong discussion, committee members and others warned about the perils of a convenience sample of providers. "I'm very leery of a convenience sample no matter how convenient it may be," said Edward Sondik, director of the Centers for Disease Control and Prevention's National Center for Health Statistics. He said that a sample that doesn't represent the country's geographic diversity could miss important environmental exposures that affect health. Relying on health care organizations could also leave out certain groups such as undocumented immigrants and the working poor, others said. (One dissenting view came from committee member Jeffrey Krischer of the University of South Florida, Tampa, who suggested that the results could be "weighted" to reflect any population.)

Several people also expressed concerns about NIH's plan to save money by relying on providers' electronic medical records. Because methods vary, there will be "problems" even with simple measurements such as a young child's height, warned committee member Bruce Gelb of Mount Sinai Hospital in New York City.

Others pointed out that NIH has already spent several years (and around $460 million of the more than $750 million spent so far on NCS) building relationships with hospitals and communities at the 40 vanguard sites. "Surely we should be trying to use some of the investment made," said Yale University epidemiologist Michael Bracken, a meeting observer.

Bracken was among investigators from 28 of the 40 vanguard sites—many of whom spoke at the meeting—who offered the advisory committee an alternative plan that would randomly sample providers within the 105 counties. Their plan lays out ways to conduct the main study within a $3 billion budget by cutting out some biological samples and tests and enrolling fewer women preconception.

Guttmacher said after the meeting that the consensus was clearly in favor of a probabilistic sample. "I think that was the overwhelming thing that came from the discussion," Guttmacher told ScienceInsider. But NIH plans to seek more input from federal statisticians and others before it makes a decision. "It's not an 'either-or.' We need to come up with an exact design at this point," Guttmacher said.

NIH hopes to have more concrete proposals by the July meeting of the advisory committee. The agency aims to issue requests for proposals for the main study before the fiscal year ends on 30 September.

Jennifer Culhane of the University of Pennsylvania and Children's Hospital of Philadelphia (CHOP) told ScienceInsider that she didn't believe NIH was seriously considering retaining the 105 counties. "Much of this [meeting] is theater," Culhane said, pointing out a recent document NIH prepared for Congress suggesting that it has already decided on a convenience sample. Once the two vanguard centers run by CHOP close down, she added, "I am 100% planning on being out of this. And I have been involved with this study for over 10 years."

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