Asthma Diagnosis Through Peak Flows

Overview

The guidelines indicate the possibility of diagnosing asthma through peak flow. This recommendation being the result of expert consensus, but the evidence is limited and contradictory. The aim of the present study is to assess whether the diagnosis of asthma through peak flow is not inferior to that of spirometry with bronchodilator test, which is the gold standard test. This is a pilot study to validate a diagnostic test. Its location is an urban health centre (CAP Sant Llàtzer of the Consorci Sanitari de Terrassa). Participation will be offered to all adult patients (18 years of age or older) who are suspected of having an asthma diagnosis. On the one hand, the reversibility will be determined by performing the peak flow test in the center with the administration of 4 puffs of salbutamol. On the other hand, PBD spirometry will be performed to complete the study and diagnosis of the patient. Peak flow is faster, cheaper, simpler, more accessible and safer for professionals in the context of an airbone pandemic.

The pandemic has had a strong impact on healthcare quality standards in Catalonia. Prioritization at the primary level of immediate care over scheduled care has led to a decrease in continuity in patient care. Asthma is a common treatable disease and exacerbations are preventable with proper staging and treatment if necessary. During the present pandemic, the ability to diagnose it through the test of choice (spirometry with bronchodilator test) has been compromised, taking into account the risks arising for health personnel to perform. This fact has conditioned that in the pandemic context it is recommended to limit its use as much as possible. These reasons led to the suspension of spirometry at the beginning of the pandemic and later, although they have been restarted with the indicated filters to improve safety for patients and professionals, it has not been possible to restore normally for issues arising from the care pressure associated with the pandemic. When the investigators reviewed the clinical guidelines, they specify that the diagnosis of asthma can also be made by measuring the maximum expiratory flow (PEF) with the peak flow. The measurement of PEF is simple, objective, non-invasive, and adds value to daily clinical practice, helping to define severity and contributing to patient self-management of the disease. The guidelines recommend that the diagnosis through peak flow is a degree of evidence C as the studies are very small samples and therefore the recommendation is based more on the consensus of experts than on the studies available. However, these guidelines propose two alternative techniques: variability and reversibility. The first is to measure with the peak flow of the daily variability of the maximum expiratory flow (PEF) in 2 weeks that would allow to diagnose asthma. But there is a difference in criteria in the variability of PEF per se between the two most frequently used guides in our environment. On the one hand, according to the criteria in the Spanish Guide to Asthma Management (GEMA) the variability required for diagnosis must be greater than or equal to 20% in more than three days in a week for a two-week record. On the other hand, in the Global Initiative for Asthma (GINA) the diagnosis would be with a minimum variability of 10% in a single week, also monitored for a period of two weeks. Both documents also explain the second technique: the possibility of using the reversibility of pre- and post-bronchodilation PEF with 4 Salbutamol poufs as a diagnostic tool. In this case, both guidelines agree that a reversibility greater than 20% would be a value to be taken into account in the diagnosis of asthma. According to the available literature, the daily variability of PEF correlates better with bronchial hyperreactivity than with symptoms and airway obstruction, when used for monitoring asthmatic patients already known to have clinical stability. This variability provides information on the risk of exacerbations, and has long been recognized as a possible diagnostic tool (8). Monitoring of PEF variability in children is insufficient to recommend this technique (9,10), although we must keep in mind that the diagnosis and monitoring of asthma in children is more difficult than in adults. Other disadvantages of PEF should also be borne in mind: low reproducibility, lack of precise reference values in population groups and may underestimate airway obstruction. Some studies suggest that the usefulness of PEF for the diagnosis of asthma should be reconsidered despite what the guidelines recommend, while others recommend its use. It is because of this need and the contradictions in the method and in the available evidence that the investigators propose to review patients who have pending spirometry with a suspected diagnosis of asthma and who have also not been able to perform them due to problems related to pandemic. People with suspected asthma criteria will have a PEF test with a peak flow at the pre- and post-administration center of salbutamol to check the diagnosis for reversibility. In the pilot study, we do not plan to carry out peak flow controls at home for 14 days to assess variability in an attempt to keep it simpler, but we do consider a larger study with more centers depending on funding possibilities. The investigators will review these data if they can be correlated with the results of the same patients in a spirometry with bronchodilator test as this technique becomes available and it is possible to perform it safely for health personnel.