All Posts tagged test

Experts find clue to yo-yo dieting

Scientists may have discovered a way of identifying dieters who are prone to piling the pounds back on after weight loss. A study at Maastricht University’s Department of Human Biology found a link between a gene involved in regulating blood pressure and post-diet weight gain in women. Women who regained weight after slimming had a high change in the concentration of a particular protein in their blood during dieting, research showed. Researchers now hope to develop a test to indicate how prone people are to yo-yo dieting.

Edwin Mariman, professor of functional genetics at Maastricht, said: “It was a surprising discovery, because until now there has been no clear link between this protein and obesity. “We do not yet have an explanation for the results, but it does appear that it should be possible within a few years to use this finding to develop a test to show who is at high risk of putting weight back on after a diet.”

Hospitals already conduct tests for the protein, known as the angiotensin I converting enzyme (ACE). But the test is currently carried out to check its activity in regulating blood pressure, rather than its concentration. Up 80% of dieters suffer from the yo-yo effect, returning to their original weight within a year.

The study looked at around 100 women aged 20 to 45, half of whom had maintained their post-diet weight and half of whom had put weight back on. The findings of the research have been published by Dr Ping Wang, a scientist in Professor Mariman’s research group, in the online scientific journal PloS ONE.

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New test can predict complications from kidney disease

Cystatin C, a blood marker of kidney function, proved significantly more accurate than the standard blood marker, creatinine, in predicting serious complications of kidney disease, in a study by researchers at the San Francisco VA Medical Center and the University of California, San Francisco. Among adults who were identified as having chronic kidney disease by high creatinine levels, the researchers found that only patients who also had abnormally high levels of cystatin C were at high risk for death, cardiovascular disease, heart failure, or kidney failure. People with high creatinine but normal cystatin C levels had risks similar to those with normal creatinine levels.

The researchers also found that a small but important segment of the study population was missed by creatinine but identified by cystatin C as being at significant risk of serious complications, according to lead author Carmen A. Peralta, MD, MAS, an SFVAMC researcher and an assistant professor of medicine in residence in the division of nephrology at UCSF.

The study of 11,909 participants appears online on December 16, 2010, in the JASN Express section of the Journal of the American Society of Nephrology. The authors analyzed patient data from two prospective studies: the Multi-Ethnic Study of Atherosclerosis and the Cardiovascular Health Study, both sponsored by the National Heart, Lung, and Blood Institute.

Principal investigator Michael G. Shlipak, MD, MPH, chief of general internal medicine at SFVAMC, said that the current study highlights a potential clinical use for cystatin C as a method for confirming a diagnosis of chronic kidney disease. Shlipak has been a leader among physicians in identifying cystatin C as an alternative, accurate, and reliable marker of kidney function.

Both cystatin C and creatinine are substances made in the body and filtered by the kidneys. High levels of the substances in the blood indicate that the kidneys are losing the ability to filter them, and thus are losing function. However, explained Peralta, creatinine is a byproduct made in muscles, so it is affected by what you eat and especially by how much muscle you have. Thus, a bodybuilder with healthy kidneys might have an elevated creatinine level because of high muscle mass, whereas a frail elderly person might have normal or even low levels of creatinine, but in fact this persons kidneys are not working well – its just that theres not much creatinine because theres not much muscle.

In contrast, cystatin C is a protein made in cells throughout the body. In studies so far, it does not seem to be that affected by age or muscle mass or diet, said Shlipak, who is also a professor in residence of medicine and epidemiology and biostatistics at UCSF.

Shlipak proposes that cystatin C, which can cost as little as $17 per test, be added as a method for confirming or staging chronic kidney disease in guidelines that are currently being formulated by nephrologists. Its vital that we have an accurate diagnostic test, because kidney disease does not show symptoms until its too late, when your kidneys have almost failed completely, he said. Being missed by creatinine is an important limitation in our current method of diagnosing kidney disease, said Peralta. Yet, she adds, being falsely identified with kidney disease through inaccurate test results can be disastrous as well. There is fear and psychological stress, particularly in communities of color, where people have a lot of friends and family members who are on dialysis, she noted. You can also be subjected to unnecessary and expensive tests and medications.

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Gluten Free Foods May Be Contaminated

Thompson and her colleagues analyzed 22 naturally gluten-free grains, seeds, and flours off supermarket shelves, only looking at products that weren't specifically advertised as being gluten-free. They tested the amount of gluten in those products against a proposed Food and Drug Administration limit for any product labeled gluten-free, 20 parts contaminant per million parts product.

Seven of the 22 products wouldn't pass the FDA's gluten-free test – and one product, a type of soy flour, had a gluten content of almost 3,000 parts per million, the authors found. Other products from the sample that weren't truly gluten-free included millet flour and grain, buckwheat flour, and sorghum flour.

The study was too small to give consumers a good idea of how common it is for these products to be contaminated or what products should make people with celiac disease especially wary, Thompson said.

But “it is a red flag,” Cynthia Kupper, the executive director of the Gluten Intolerance Group of North America, who was not involved with the research, told Reuters Health.

Even companies that do explicitly label their products as gluten-free, she said, might not always test products they assume won't contain any gluten. The study “is a wake-up call to the food industry,” said Kupper. Companies “need to make sure (their products) are truly gluten-free.”

Without an FDA regulation in place, there is still no hard-and-fast government definition of what gluten-free means, Thompson said.

That makes it harder to keep companies that might skimp on their testing accountable.

“It's hoped but certainly not assumed that manufacturers who are putting the (gluten-free) label on their single-ingredient grains and flours are testing their ingredients,” Thompson said. “Do all manufacturers test? Probably not.”

Under the proposed gluten-free labeling rule, the FDA could conduct inspections of manufacturers that claim their products are gluten-free and analyze those products.

Thompson and Kupper agreed that more research needs to be done to find out the scope of the contamination problem. In the meantime, Thompson said, people with celiac disease are probably better off purchasing grains, seeds, and flours with the gluten-free label. The products can't be guaranteed to be completely free of gluten, but it is more likely that they will have been tested, she said.

SOURCE: http://link.reuters.com/zev57m Journal of the American Dietetic Association, June 2010.

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What to expect on your first visit

An Accredited Practising Dietitian is a health professional who is a food and nutrition expert. Dietitians complete a university course in order to be able to understand your medical/surgical condition and nutritional needs and adapt these into practical dietary advice.
Your first appointment is likely to take 45 – 60 minutes and sometimes longer. You need to bring the following to your appointment: 
  • Your referral letter or EPC (Medicare form) from your GP (if you were referred)
  • Your food record / diary if you have been asked to keep one.
  • A list of medications.
  • Dietary advice previously given.
  • Blood sugar records, if applicable.
  • Test results, if applicable.

You can bring a friend, relative or carer to the appointment if you find this helpful.

At the appointment, Nastaran will:

  • Introduce herself and welcome you.
  • Discuss the reason you have been referred.
  • Ask you questions about the types of food you eat, how you cook your foods and when you eat.
  • Ask to measure your height and weight.
  • Agree the changes you may wish to make, to meet your individual needs.
  • Provide you with written information.

Your doctor will be informed of any dietary treatment recommended (if your were referred).

If Nastaran needs to see you again, she will agree this with you and explain how the followup

appointment is made and how long this will take. Generally followup appointments are 20-30 minutes long.

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No Clear Criteria for Diagnosing Food Allergies

Food allergies, by some accounts, affect about 4 percent of adults and 5 percent of children under the age of 6 in the United States, though this study raises questions about the reliability of such figures.

Food allergies can cause a variety of problems, ranging from mild skin rashes or nausea to a life-threatening, whole-body reaction known as anaphylaxis. The allergies can also have serious effects on patients' social interactions, school and work attendance, family economics and overall quality of life. “It's a life-defining diagnosis in a way,” said Chafen.

The National Institute of Allergy and Infectious Diseases is working on new clinical practice guidelines and, as part of its efforts, enlisted Chafen and her colleagues to review the current evidence on food allergies.

The researchers started their work by sifting through thousands of scientific papers, published between 1988 and 2009, that focused on the four foods — milk, eggs, fish and peanut and tree nuts — responsible for more than half of all allergies. They ultimately reviewed 72 studies, including one meta-analysis on prevalence, 18 studies on diagnosis, 28 studies on management, and four meta-analyses and 21 additional studies on prevention.

When examining the literature, the researchers found there was no universal definition of “food allergy,” in spite of NIAID's defining it as an “adverse immune response” that is “distinct from other adverse responses” such as a food intolerance. In fact, 82 percent of the studies provided their own definition of food allergy.

“This validates the idea that there exists a great deal of complexity and confusion in the field of food allergy, even at the level of the medical literature,” said co-author Marc Riedl, MD, MS, section head of clinical immunology and allergy at UCLA.

Along the same lines, there was a lack of uniformity for criteria in making a diagnosis. The current gold standard is the food challenge, during which a physician gives a patient a sample of the suspected offending food, sometimes in capsule form, and then monitors for allergic reaction. However, this test requires specialized personnel, is expensive and has a risk of anaphylaxis. Office-based tests were used to diagnose many patients; these include a skin-prick test, during which a dilute extract of the potential allergen is placed on the skin, and a blood test that determines the presence of food-specific allergic antibodies known as IgE.

As the researchers discuss in their paper, the concern with the latter two tests is that they're not definitive: Patients with non-specific symptoms, such as a rash or digestive troubles, and positive skin-prick or blood tests actually have less than a 50 percent chance of having a food allergy. In order to make a proper diagnosis, they pointed out, physicians need to evaluate the data within the context of a patient's history and have a great understanding of symptoms consistent with true food allergy.

What this means, then, is there is a potential for the overdiagnosis of food allergy.

“I frequently see patients in my clinical practice who have food intolerance, but have previously had inadequate or inappropriate evaluation and been told they have a 'food allergy',” said Riedl. “This causes a great deal of unnecessary anxiety and concern for the patient.”

Previous studies have tried to determine whether the skin-prick or blood test is superior over the other, but in reviewing the evidence, Chafen and her colleagues found “no statistical superiority in either test.” They also found generally inconclusive results from 10 previous studies in which the tests were combined, in an effort to improve diagnostic accuracy.

“I was very surprised,” said Chafen. “I'm a general internist and I thought diagnostic strategies were more-studied.”

In terms of treatment, Chafen said expert opinion is that an elimination diet — having the patient stop consuming the food that causes the allergic reaction — is the most common. Although the approach is a common-sense one (“If a patient breaks out in hives repeatedly after drinking milk, it's your instinct as a physician to say, 'Don't drink milk,'” Chafen said), the researchers found the treatment hasn't been well-studied.

It would be unethical to conduct controlled studies of elimination diets for patients with serious, life-threatening allergic reactions, but as pointed out in the paper, there are few studies of this approach on patients with relatively minor symptoms.

“In these instances, the benefits of an elimination diet are uncertain based on published evidence and potential benefits need to be weighed against the potential nutritional risks of such a diet, particularly in children,” the researchers wrote.

Chafen and her colleagues also found that immunotherapy, a treatment in which the body's immune system is altered by administering increasing doses of the allergen over time, appeared to be effective at eliminating symptoms in the short term. Immunotherapy isn't a licensed method for allergy treatment, but the researchers urged more study on its long-term effect and safety.

In all, the researchers concluded, the food-allergy field is in need of uniformity in the criteria for what constitutes an allergy and a set of evidence-based guidelines upon which to make this diagnosis. NIAID, which put together an expert panel and has reviewed the group's analysis, is planning to finalize such guidelines later this summer.

As for Chafen, who sees patients with potential food allergies, these findings have encouraged her to rely more on specialists to help clinch a diagnosis. “People need to be seen by someone with a deep understanding of diagnostic tests and criteria,” she said. “The distinction between food intolerance and food allergy is really important.”

The study was funded by NIAID. Other Stanford authors on the study are Dena Bravata, MD, a PCOR affiliate; and Vandana Sundaram, MPH, assistant director of research for CHP/PCOR. Paul Shekelle, MD, PhD, with the RAND Corp.'s Southern California Evidence-Based Practice Center and the West Los Angeles VA Medical Center, is the senior author.

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