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Editorial Asthma Pulmonary Function Testing in Preschool Asthmatic Children Luís Miguel Borrego 1,2 and Mário Morais-Almeida 3,4 1. Allergy Center, CUF Descobertas Hospital, Lisbon, Portugal; 2. CEDOC, Chronic Diseases Research Center, NOVA Medical School, Lisbon, Portugal; 3. Allergy Center, CUF Descobertas Hospital and CUF Infante Santo Hospital, Lisbon, Portugal; 4. CINTESIS – Center for Research in Health Technologies and Information Systems – Faculty of Medicine, University of Porto, Porto, Portugal Abstract Pulmonary function tests (PFT) are usually useful to confirm the diagnosis, as well as for guidance to therapy and also to clarify the prognosis of several respiratory diseases, but only recently it gained interest in preschool aged children. Published papers have shown the feasibility of respiratory function testing in preschool aged children, as in the context of clinical investigation, as in clinical daily practice, but more investigation is needed to demonstrate PFT usefulness, particularly in clinical correlation and prospective follow-up of preschool asthmatic children. Keywords Asthma, preschool children, pulmonary function tests, standardisation Disclosure: Luís Miguel Borrego and Mário Morais-Almeida have nothing to disclose in relation to this article. This article is a short opinion piece and has not been submitted to external peer reviewers. No funding was received in the publication of this article. Open Access: This article is published under the Creative Commons Attribution Noncommercial License, which permits any non-commercial use, distribution, adaptation and reproduction provided the original author(s) and source are given appropriate credit. Received: 17 April 2016 Published Online: 3 May 2016 Citation: European Respiratory & Pulmonary Diseases, 2016;2(1):16–7 Correspondence: Luís Miguel Borrego, Allergy Center, CUF-Descobertas Hospital, 1998-018 Lisbon, Portugal. E: [email protected] Pulmonary function tests (PFT) are usually useful to confirm the diagnosis, as well as for therapy guidance and also to clarify the prognosis of several respiratory diseases. 1 These tests have been used for decades in adults but only gained relevance in preschool aged children in recent years. In this age group there are some difficulties in cooperation and coordination, and it has been already proved the inadequacy of the adults’ criteria for PFT in preschool age children. 2,3 In preschool children, it is not possible to measure static lung volumes, since children do not breathe against a closed valve, but specific airway resistance (sRaw) can be calculated by measuring changes in airflow relative to changes in plethysmographic volume without a closed shutter. 4 Spirometry can be performed using animated software with experienced and highly skilled technicians. 5 The American Thoracic Society (ATS) and the European Respiratory Society (ERS) have published a joint paper with recommendations for acceptability and reproducibility criteria in preschool children, 1 in order to allow the standardisation of methods and practices. Moreover, in this age group there are reference equations for spirometry 6 and sRaw. 7 Regarding animated spirometry, reporting forced expiratory volumes (FEV) of less than one second has increased the number of successful PFT in younger children, where reporting FEV 0.75 has been useful. Previously published papers have shown the feasibility of respiratory function testing in preschool children, in the context of clinical investigation 3,4 and in clinical daily practice. 5,8 16 Studies that have focused on this issue reported success rates in animated spirometry of 85–90%, 3, 5, 8, 9 and 75–80% for sRaw. 5,8,10 A study conducted by Borrego et al. demonstrated the reproducibility of these measurements over time, and differences depending on the clinical diagnosis (asthma versus recurrent wheeze or chronic cough) in this age group. 11 A positive bronchial challenge test is important to assist the diagnosis of bronchial asthma, and has been clearly defined in older children and adults (increased FEV 1 over 12% and 200mL). 12-14 In preschool children this cut-off hasn´t have been clearly defined yet. In the former study, the limit of 14% for FEV 0.75 has been proposed has the criterion for the positiveness of this test, when comparing asthmatics to healthy subjects. 11 Some studies performed by our group aimed to compare in clinical daily practice the classical bronchodilator (BD) test (FEVt>12%) used for adults with the 14% cut-off mentioned above. In fact, preschool age children with asthma, with non-atopic recurrent wheeze and with chronic cough have performed animated spirometry with BD test, and it has been proved that the 14% cut-off for BD could better differentiate asthmatic children from the remaining groups. 5,8 However, the isolated interpretation of a positive BD test must be used with caution, and the basal spirometry must be taken into account since in a recent study also carried out by our group, we have shown that an isolated BD test (>14%) with normal basal spirometry can also be found in some preschool age children without asthma. 15 TOU C H ME D ICA L ME D IA