Which of the following is a common abnormal finding that may prompt further testing of a newborn?

Inconclusive metabolic screening is a critical reason for further testing in newborns. Metabolic screenings are designed to detect certain genetic, metabolic, and endocrine disorders early in life, some of which can have serious health implications if not addressed promptly. An inconclusive result suggests that there may be underlying issues that need additional investigation to ensure the newborn's health and well-being. It is essential to identify these disorders early to allow for timely intervention and management, which can significantly improve outcomes for the infant.

Healthy weight and size, normal reflex responses, and passing hearing screening are all indicators of a newborn's well-being and suggest that the infant is developing appropriately. These findings do not warrant further testing, as they are generally considered normal and healthy outcomes in newborn assessments.