Spirometric Phenotypes in Schoolchildren: Longitudinal Study of Preschool Wheezers and Controls

Aim Knowledge of spirometric patterns beyond obstruction with low forced expiratory volume in 1 s (FEV 1 ) remains limited. We assessed the prevalence, characteristics, and transitions of unimpaired spirometry, preserved ratio impaired spirometry (PRISm), dysanapsis and obstruction with low FEV 1 (Obst‐low‐FEV 1 ) at 7 and 11 years. Methods We included former preschool wheezers (cases; n 7 = 102 and n 11 = 97) and healthy controls (37 at both ages), of whom 87 cases and 20 controls had spirometry at both ages. Assessments comprised questionnaires, clinical examinations, spirometry, bronchodilator responsiveness (BDR), fractional exhaled nitric oxide (FeNO) and blood sampling. Results PRISm was the most common pathological phenotype in cases (17.6%/14.4%, age 7/11) and controls (13.5% at both ages). Among cases, Obst‐low‐FEV 1 was more common (8.8%/11.3%, 7/11 years) than dysanapsis (5.9%/8.2% age 7/11). Phenotypes changed in 54% of participants between 7 and 11 years. BDR > 10% occurred across all phenotypes but was significantly associated with dysanapsis (OR adj = 2.88, CI 1.00–8.27) and Obst‐low‐FEV 1 (OR adj = 16.14, CI 4.89–53.30) among cases. Higher FeNO was associated with Obst‐low‐FEV 1 (OR adj = 1.03, CI 1.00–1.07), whereas lower FeNO (OR adj = 0.90, CI 0.82–1.00) and sensitization (OR adj = 6.22, CI 0.97–39.77) were associated with dysanapsis in cases. Conclusion PRISm and dysanapsis are common, dynamic phenotypes differing from Obst‐low‐FEV 1 in their clinical and inflammatory profiles.