Prematurity and Respiratory Outcomes Program (PROP)

The primary goal of the PROP studies is to identify biomarkers (biochemical, physiological and genetic) and clinical variables that are associated with and thus potentially predictive of pulmonary status in preterm infants up to 1 year corrected age. An objective and validated measure of pulmonary outcome at 1 year does not currently exist. Some promising measures are in development but not yet ready for use in a multi-center large clinical study.

Moreover, the burden of chronic respiratory illness on the infants and their families is of utmost importance. A composite primary outcome of morbidity that is based on serial parental reports of respiratory symptoms, medications, hospitalizations and dependence on technology during the first year of life has been developed.

Data collection for the outcome assessment will be based on interviews conducted with the infant's main caregiver at 3, 6, 9 and 12 months corrected age. The time frame for data collection is based on questions "since last contact." Numerous epidemiological studies of asthma have used parental or self report of symptoms, physician-diagnosed asthma and allergies, or the use of medications (which may abrogate symptoms) as critical outcomes.

Survey items selected for the determination of the primary outcome will be focused on the following four domains, with any positive response to any element identifying morbidity:

• Respiratory medications: inhaled bronchodilators, inhaled steroids, systemic steroids, methylxanthines, diuretics, pulmonary vasodilators
• Hospitalizations for cardiopulmonary causes: any hospitalization regardless of duration
• Symptoms: any wheeze, cough without cold
• Home technology dependence: use of home oxygen, ventilator or continuous positive airway pressure (CPAP or BiPAP) of any duration since last contact

The primary outcome will be dichotomous, and defined as "No substantial post-prematurity respiratory disease" or "Post-prematurity respiratory disease." To be classified as having post-prematurity respiratory disease, infants must have a positive response in at least 1 of 4 morbidity domains during at least 2 separate parental interviews. Quarterly data collection up to 1 year corrected age will allow us to identify phenotypes based on the trajectory of post-prematurity respiratory disease and how these different trajectories predict later lung function and the diagnosis of asthma, if we continue to follow this cohort of children.

During hospitalization, all centers will obtain samples of tracheal aspirate, urine and saliva (for DNA extraction) from enrolled infants. At 36 weeks PMA, infants will have respiratory assessments dependent upon their respiratory status: i) respiratory inductive plethysmography (RIP) assesses alterations in tidal breathing resulting from reduced lung compliance and airway obstruction, ii) and a room air challenge (RAC).

Inclusion criteria

• Infants who are less than or equal to 7 days old
• Gestational Age (GA) between 23 weeks and 0/7 days and 28 weeks and 6/7 days

Exclusion criteria

• Infants who meet any of the following conditions will be excluded from the PROP cohort:

• The infant is not considered to be viable (decision made not to provide life-saving therapies)
• Congenital heart disease (not including PDA and hemodynamically insignificant VSD or ASD)
• Structural abnormalities of the upper airway, lungs or chest wall
• Other congenital malformations or syndromes that adversely affect life expectancy or cardio-pulmonary development
• Family is unlikely to be available for long-term follow-up