Study	Reason for exclusion
Kaapa 1983	RCT of indomethacin for PDA ‐ symptomatic infants were not excluded. The median timing of first dose of indomethacin was less than 24 hours of age
Merritt 1981	Not a trial of asymptomatic PDA. All randomised infants had clinical evidence of a left to right shunt and were therefore symptomatic
Mullett 1982	No determination made of symptoms related to PDA. Infants included with both asymptomatic and symptomatic PDA
Van Overmeire 2001	A randomised controlled trial of early indomethacin treatment. Infants noted to have one of three levels of left to right shunt at randomisation ‐ minor, moderate or severe; i.e. not all infants were asymptomatic
Vogtmann 1988	No attempt made to identify infants with PDA ‐ all VLBW infants eligible with or without PDA. Indomethacin administered after 24 hours of age, and therefore unable to determine easily whether truly a trial of prophylactic indomethacin or treatment for asymptomatic PDA