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24-06-2013 | Respiratory | Article

Spirometry essential for asthma diagnosis in morbidly obese


Free abstract

medwireNews: Researchers say that pulmonary function testing must be performed in morbidly obese patients to confirm a diagnosis of asthma after they found a high prevalence of, not only overdiagnosis but, underdiagnosis among such patients.

Their findings, published in Respiratory Medicine, showed that nearly one third of their sample had undiagnosed asthma, despite experiencing comparable symptoms to diagnosed patients, while others were taking inhaled corticosteroids unnecessarily.

The study included 86 patients with a body mass index of at least 35 kg/m2 who were undergoing screening for bariatric surgery.

Of the 32 patients with physician-diagnosed asthma, the diagnosis could not be confirmed in 41% who failed to show bronchodilator reversibility or respond to a negative provocation test. Conversely, in the remaining 54 patients, 31% had asthma symptoms, reversible airway obstruction, or airway hyperreactivity, despite never having a diagnosis from a physician.

Patients who were underdiagnosed with asthma had a similar level of symptoms to those who were correctly diagnosed or overdiagnosed, report authors Astrid van Huisstede (Sint Franciscus Gasthuis, Rotterdam, the Netherlands) and colleagues.

They say the reasons why these patients did not receive a diagnosis are unclear but are likely to be related to self-misperception, and possibly physician misperception. They suggest that the patients related their symptoms to obesity rather than respiratory disease and therefore did not discuss them with a physician.

Additionally, the team notes that patients in this group had significantly greater mean abdominal circumference, which could indicate that central obesity obstructs the peripheral airways, altering asthma perceptions.

There have been several reports of asthma overdiagnosis in the morbidly obese but the authors say that all recent studies have excluded patients without an asthma diagnosis, precluding the exploration of underdiagnosis.

They conclude: "A diagnosis of asthma based on symptoms alone is unreliable in the morbidly obese, and pulmonary function testing is an essential part of the diagnosis of asthma in the morbidly obese."

"As a result of the most likely high prevalence, potential health risk and the high economic burden of misdiagnosis, characterization of these patients is important," they add.

medwireNews ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013

By Kirsty Oswald, medwireNews Reporter