The primary end point was efficacy , which was defined as a rate of increase in total serum bilirubin of less than 0.2 mg per deciliter per hour for infants up to 72 hours of age or a decrease in total serum bilirubin for infants older than 72 hours of age who received at least 5 hours of phototherapy ; we prespecified a noninferiority margin of 10 % for the difference in efficacy rates between groups .