The usefulness of clinical examination for the diagnosis of obstructive airway disease (OAD) has been poorly studied. The Clinical Assessment of the Reliability of the Examination–Chronic Obstructive Airways Disease group is a multinational group that designed a study to determine which elements of a clinical evaluation aid in predicting OAD.

Twenty investigator groups (consisting of at least one clinician and one spirometrist) enrolled consecutive adult patients in three categories: patients known to have chronic OAD, those suspected of having OAD and those who were neither known to have nor suspected of having OAD. Patients with reversible airway disease (i.e., asthma), those with terminal illness and those who could not safely be without bronchodilators until after spirometry were excluded. Information assessed included: smoking history, self-reported history of chronic OAD, laryngeal height (distance between the top of the thyroid cartilage and the suprasternal notch), laryngeal descent (difference between the maximal and minimal heights) and wheezing. Spirometry was performed within 30 minutes of the clinical examination. OAD was defined as a forced expiratory volume in one second (FEV₁⁾ and FEV₁-forced vital capacity (FVC) ratio less than the fifth percentile.

Of the 332 patients recruited, 309 patients were available for analysis. The likelihood ratio for OAD was 220 in patients who had all of the following: a self-reported history of chronic OAD, a smoking history of more than 40 pack-years, older than 45 years and a maximum laryngeal height of 4 cm or less. Patients with none of these factors had a likelihood ratio of 0.13. If patients were younger than 45 years, OAD was virtually always ruled out. The presence of auscultated wheezing and a maximum laryngeal height of 4 cm or less made OAD more likely, but not sufficiently more to act as diagnostic parameters.

The authors conclude that a self-reported history of chronic OAD, a pack-year smoking history, age and a maximum laryngeal height can be useful for predicting OAD. If spirometry is available, it should be performed because it can definitely diagnose the obstructive airway disease; however, in the absence of spirometry, the proposed model provides diagnostic support.