Tailored interventions based on sputum eosinophils versus clinical symptoms for asthma in children and adults

A new review suggests that asthma treatment based on tests of fluid coughed up from the lungs could reduce the frequency and severity of flare-ups in adult asthma patients.

However, lead review author Helen Petsky said, “The practice cannot be recommended in all settings until more studies are available,” adding that no research shows this practice is effective in children.

Asthma patients and their doctors typically head off asthma attacks by tracking the frequency of symptoms such as wheezing and coughing, and use lung function tests to identify when airways become narrowed or inflamed.

Testing lung secretions offers another way to measure airway inflammation objectively and can help patients and doctors manage asthma, said Petsky, a respiratory nurse and project coordinator at the Royal Children's Hospital in Queensland, Australia.

Petsky and co-authors evaluated research on the use of sputum analysis, a laboratory test performed on fluid coughed up from the lungs.

When asthma patients experience the airway narrowing that precedes an asthma flare, they produce two kinds of white blood cells that are signs of inflammation. These cells —called eosinophils and neutrophils — show up in phlegm. Higher numbers of eosinophils indicate more severe airway inflammation.

This review looked at studies that compared sputum analysis monitoring to traditional symptom and lung-function monitoring. Data came from 221 adult patients in three studies conducted between 2002 and 2006.

The studies took place in the Czech Republic, the United Kingdom, Canada and Brazil.

The review appears in the current issue of The Cochrane Library , a publication of The Cochrane Collaboration, an international organization that evaluates research in all aspects of health care. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing trials on a topic.

Patients monitored with sputum analysis were significantly less likely to experience asthma flares, had a reduced frequency of flares and went longer without experiencing flares when compared to patients who only monitored asthma symptoms and lung function, the analysis showed.

“Adults who have severe and frequent asthma attacks could benefit from having their treatment based on inflammatory marker cells that are found in their sputum,” Petsky said.

Sputum monitoring might reduce the need for steroid medications prescribed to treat airway inflammation, the researchers wrote. However, the findings did not show significant differences in corticosteroid use between the treatment and control groups.

Likewise, there was no difference in asthma symptoms or in quality-of-life scores between the control and treatment groups, the review authors reported.

Petsky said she was surprised that none of the trials included data on children. Of the 11.7 million Americans who experience asthma attacks every year, 4 million are under age 18, according to the American Lung Association.

However, it can be difficult to obtain sputum samples in young children, which might contribute to the lack of data in the pediatric population, the review authors say.

The authors concluded that while sputum analysis could prove beneficial for adults with severe asthma, current research does not justify routine sputum analysis since there have been few trials, variable definitions of asthma exacerbations and uneven cut-off points for sputum eosinophils.

Miles Weinberger, M.D., director of the division of allergy and pulmonary diseases at the University of Iowa/Children's Hospital of Iowa, concurred.

In particular, Weinberger suggested that the authors failed to place enough emphasis on the difficulties associated with obtaining sputum samples, calling the lab test “a clumsy surrogate for asthma control.”

During a severe asthma flare-up, patients might cough up sputum for analysis, but under normal circumstances, patients would need to undergo a sputum induction by breathing in an aerosolized salt solution.

“It's uncomfortable, it's time-consuming and it requires special lab facilities to examine the sputum. I can't imagine it being done in routine clinical care,” Weinberger said.

In asthma patients, sputum induction can even induce bronchospasm, a shrinking of the airways in the lungs that can lead to wheezing, chest pain, coughing and difficulty breathing, he said.

“I think careful clinical monitoring and pulmonary function testing at the time of assessment is just as practical and just as good if done well,” Weinberger said.

Petsky HL, et al. Tailored interventions based on sputum eosinophils versus clinical symptoms for asthma in children and adults (Review). Cochrane Database of Systematic Reviews 2007, Issue 2.

The Cochrane Collaboration is an international nonprofit, independent organization that produces and disseminates systematic reviews of health care interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions. Visit http://www.cochrane.org for more information.

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