Characterising airway obstructive, dysanaptic and PRISm phenotypes of prematurity-associated lung disease

Introduction Although obstructive airway disease has been shown to be associated with prematurity, other spirometry phenotypes are less well described. Objectives We characterised abnormal spirometry phenotypes in preterm-born children, including prematurity-associated obstructive lung disease (POLD, forced expiratory volume in 1 s (FEV 1 )<lower limit of normal (LLN), FEV 1 /forced vital capacity (FVC)<LLN), prematurity-associated preserved ratio of impaired spirometry (pPRISm, FEV 1 <LLN, FEV 1 /FVC≥LLN) and prematurity-associated dysanapsis (pDysanapsis, FEV 1 ≥LLN, FEV 1 /FVC<LLN), and associated them with early life factors, bronchodilator responsiveness and fractional exhaled nitric oxide (FE NO ). Methods 768 children, aged 7–12 years, underwent FE NO measurements and spirometry before and after salbutamol. Groups were compared using parametric tests; multinomial regression was used. Results 22.6% of 544 preterm-born (mean gestation: 31 weeks) and 9.2% of 195 term-born children, with satisfactory data available, were classified into one of four abnormal spirometry groups. Each phenotype was generally more prevalent in preterm-born children than in the term-born children. For the preterm group, POLD-reversible (4.4%) was associated with increased FE NO , bronchopulmonary dysplasia (BPD) and intrauterine growth restriction. POLD-fixed group (3.3%) did not have increased FE NO but was associated with BPD. 41% of the pDysanapsis group (5.9%) had bronchodilator response, 31% had increased FE NO and was associated with postnatal weight gain. In the pPRISm group (9%), 13% responded to bronchodilators, FE NO was not increased and was non-significantly associated with body mass index (p=0.064). Conclusions Further to airway obstruction, we describe airway dysanapsis and pPRISm spirometry phenotypes in survivors of prematurity, both of which have poor outlook in other disease groups. By identifying specific phenotypes, targeted therapy can be developed to improve long-term outcomes.