Fine Crackles – Velcro-like Sounds – in Exams May Be IPF Screening Tool

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by Vanda Pinto |

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Listening for fine crackles — a sound like Velcro strips being separated — during routine lung checks with a stethoscope may help healthcare providers to reach an early diagnosis of idiopathic pulmonary fibrosis (IPF), a Canadian study reports.

Doctors are almost 13 times more likely to hear such fine crackles, alone or in combination with coarse crackles, originating from the lungs of IPF patients than from the lungs of people with other forms of interstitial lung disease (ILD), according to the study.

These findings suggest that abnormal breath sounds, or fine crackles, heard during examinations with a stethoscope — known as lung auscultation — could be used as a sensitive and practical screening tool that may lead to an early diagnosis and treatment of IPF patients.

The study, “Fine crackles on chest auscultation in the early diagnosis of idiopathic pulmonary fibrosis: a prospective cohort study,” was published in the journal BMJ Open Respiratory Research.

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IPF is an ILD of unknown cause in which lung tissue becomes increasingly scarred, resulting in progressive lung function decline. According to researchers, the disease should be considered in all adults who have unexplained difficulty breathing combined with a cough, crackling breath sounds, and finger clubbing.

But the diagnosis — and the initiation of treatment — for IPF can be delayed by two years or more, which can lead to increased death rates, previous data suggest.

The best noninvasive test for diagnosing ILDs is widely considered to be a high-resolution computed tomography or HRCT chest scan. However, this method is too costly and impractical to be used as a screening tool.

Some studies have suggested that assessing the presence of fine crackles during lung examinations — considered a more practical assessment than HRCT — might be the only realistic way of diagnosing IPF earlier. However, no study so far has explored this possibility in depth.

Now, researchers in Canada, along with a colleague from the UAE, investigated for the first time whether fine crackles heard during lung examinations could be useful in diagnosing IPF and other ILDs.

The team assessed the presence and type of crackling sounds heard during chest auscultation in all new patients referred to the ILD Clinic at the Kingston Health Sciences Center (KHSC), in Ontario, between 2013 and 2018.

Participants in the study had no previous diagnosis of IPF and some had no symptoms and/or had normal lung function. All patients eventually diagnosed with IPF or other ILDs who had at least two clinic visits were included in the study.

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A total of 21 clinicians with different levels of experience and training conducted the chest examination with their own stethoscope and recorded the presence and type of crackles (fine or coarse). As part of the study, the healthcare providers were given several examples of what fine and coarse crackles may sound like.

Fine crackles can sound like Velcro strips being separated or the noise that comes from rubbing hair between fingers, while coarse crackles may sound like someone is walking on ice or squeezing a paper bag.

A total of 290 patients, 58% of whom were men, were evaluated in the study. Nearly half (47%) of the participants were obese, and 27% showed signs of emphysema — a severe form of chronic obstructive pulmonary disease (COPD) — on chest CT scans. A total of 10% of the patients had COPD.

Lung function was evaluated using several parameters, including forced vital capacity (FVC), total lung capacity (TLC), and carbon monoxide diffusing capacity (DLco). FVC measures the total amount of air a person is able to exhale after a deep breath. Meanwhile, TLC assesses the maximum amount of air a person is able to breathe, and DLco measures the lungs’ ability to transfer oxygen to the bloodstream.

At the first clinic visit, 54% of ILD patients had normal FVC, 50% had normal TLC, and 16% had normal DLco values. A total of 129 patients (45%) were ultimately diagnosed with IPF and the remaining 55% with other ILDs.

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The researchers reported that, at the first visit, 93% of IPF patients had fine crackles in lung auscultation, alone or combined with coarse crackling sounds, compared with 73% of patients with other ILDs.

At the following clinic visit, 90% of patients who had fine crackles — with or without coarse crackles — and 40% of those with coarse crackles on the initial clinic visit continued to show the same type of crackling sounds.

Statistical analysis revealed that the odds of hearing fine crackles — alone or in combination with coarse crackles — during lung auscultation were almost 13 times higher among individuals with IPF than in patients with other ILDs.

Importantly, no other factors were found to have an influence on the correct identification of crackles. Such factors included the presence or absence of coughing, shortness of breath, emphysema, COPD, obesity, the doctor’s experience, FVC, TLC, or DLco values.

“Our study shows that fine crackles are present in almost all patients with IPF, including asymptomatic patients and patients with normal [lung function tests],” the researchers wrote, noting that such crackles “can be properly identified regardless of patients having emphysema, COPD, obesity or the experience of the clinician performing the chest auscultation.”

The researchers noted that early diagnosis is particularly important “given the current availability of antifibrotic drugs that can slow down the progression of IPF.”

“Our results suggest that fine crackles on chest auscultation are a sensitive, robust and useful screening tool that can lead to early diagnosis and treatment of patients with IPF, and likely other ILDs,” they concluded.

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