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RESEARCH BRIEFS Finding a Better and Cheaper Way to Diagnose Iron DeficiencyResearchers at Children's Hospital report in the June 16 Journal of the American Medical Association that they have identified the most powerful diagnostic parameter for detecting iron deficiency in young children. If this research is confirmed in larger studies, diagnosis of this condition could become simpler, cheaper, and more precise. Iron deficiency is one of the most common nutritional deficiencies and is the leading cause of anemia in children. Though correctable with iron supplementation, the condition can impair cognitive development in children and is often diagnosed too late to reverse this and other complications. The best way to catch the problem early has been unclear. In recent years, two new markers to indicate a child's iron stores have joined six older, biochemical and hematological ones, adding a measure of confusion. Led by Orah Platt, HMS professor of pediatrics at Children's, the scientists used all of the above parameters to analyze the blood of 210 children whose mean age was 2.9 years. Forty-three children turned out to be iron deficient, and 24 of these had progressed to anemia. The scientists found that the hemoglobin content in reticulocytes-newly formed red blood cells-was the only significant predictor of anemia due to iron deficiency. Other frequently assessed markers, such as plasma ferritin levels, had no predictive power. The authors caution that their approach, which involves a complete blood cell count and reticulocyte analysis, must next be compared directly with the traditional biochemical panel in a clinical trial. It also needs to be tested on larger, unselected groups of children. But if their approach holds up, it could slash the cost of diagnosis by as much as 75 percent. It would also obviate the need for drawing blood into serum tubes and heparin tubes. Instead, the toddlers and preschoolers would get away with a simple finger prick. First author Carlo Brugnara, HMS associate professor of pathology at Children's, worked with David Zurakowski, HMS instructor in radiology at Children's, and colleagues. —This and briefs below by Justin Yarrow What the Brain Does When Making Spatial DecisionsAs a rat scurries for a treat at the end of a maze, its brain is constantly tracking and updating the rat's location. Researchers do not know how this spatial information is encoded, but studies indicate that theta oscillations (electrical activity with a frequency of 4 to 8 Hz) in the hippocampus are present in an animal making spatial decisions. In humans, imaging of the brain during spatial decision-making has relied upon techniques that can localize brain activity but are not capable of determining if theta oscillations occur. Michael Kahana, Joseph Madsen, assistant professor of surgery at Children's Hospital, and colleagues report in the June 24 Nature that they have directly measured brain activity in people during maze navigation. To do so, they utilized an array of electrodes implanted as a diagnostic tool under the skull of epilepsy patients. The array gives a fine map of the electrical activity of the brain. The researchers monitored the map as the patients were trained and tested on a computer-generated maze.
Kahana and colleagues have found that indeed, humans do exhibit theta oscillations during spatial navigation. They suggest that these are specifically linked to spatial navigation since there is an increase in the duration of theta oscillations in longer mazes and during the testing period, when there are no clues to follow as there are in the training period. "In 45 electrodes, theta episodes occurred more frequently during test trials than during study trials. No electrodes showed the reverse pattern," write the authors. Despite finding evidence for the role of theta oscillations in human spatial navigation, the authors note that more work is needed to see if the oscillations they measured from the cortical surface emanate from the hippocampus as they do in rodents. MR May Improve Heart ImagingX-ray angiography, the only technique routinely used to image the arteries of the heart and assess the extent of heart disease, is expensive and invasive. Many attempts to develop a reliable noninvasive method to evaluate the coronary arteries have come up short. Rene Botnar and colleagues, led by Warren Manning, associate professor of medicine at Beth Israel Deaconess, give evidence in the June 25 Circulation that 3-D magnetic resonance angiography (MRA) might finally succeed in reaching this goal. MRA relies on the same principles as MRI. Using a strong magnetic field, one can image soft tissues throughout the body by measuring the way different organs and tissues absorb and emit energy of the magnetic field. Previously, MRA required training a patient to hold his breath 30 to 40 times throughout the procedure, and the images still were marred by high background and low resolution. Now, Botnar and colleagues have made MRA a technique allowing patients to breathe freely during their 30-minute scan and yielding clearer images of diseased arteries. Their technical advances are two-fold: they use software that tracks the heart and adjusts for movements caused by breathing, and they apply a preparatory pulse of the MRI device to reduce the background caused by cardiac and skeletal muscle. The authors write, "The T2prep (pulse) resulted in a 123 percent increase in the contrast-to-noise ratio," and "coronary edge definition was improved by 33 percent." Studies are currently under way to determine if this procedure, which costs one quarter of an X-ray angiogram, is as effective. Public Health Consequences of Global WarmingConsequences in the wake of a hurricane, wildfire, or other natural disaster extend far beyond the people acutely affected. The images and stories reported in the media are horrific, but the underlying climatic causes for such disasters and their long-lasting and far-reaching effects may be of greater concern. In the July 16 Science Paul Epstein, associate director of the Center for Health and the Global Environment at HMS, comments on a paper describing the successful use of climate and vegetation tracking to predict the outbreak of Rift Valley fever epidemics. In an essay titled "Climate and Health," he summarizes work connecting climate change and disease and presents a public health challenge for the future. "Connections between climate and disease are not new," he writes, but the increase in the world's population and the extent of the effect humankind has had on the climate are. As an example of the complexity of the situation, Epstein relates how with a one degree (Celsius) rise in temperature, the atmosphere holds 6 percent more water vapor. This "boosts humidity and heat indices, fuels storms, and reinforces the greenhouse effect" at a climatic level and "generates more tropical-like downpours that create perfect breeding grounds for mosquitoes; propel rodents from burrows; and flush nutrients, chemicals, and microorganisms into waterways." The costs are shared by both developed and developing countries. Direct economic losses caused by extreme weather totaled $89 billion worldwide in 1998 alone, whereas for the entire decade of the 1980s, the total was $55 billion. |
