Evidence-Based Medicine recently published a thoughtful commentary by Montori et al,¹ addressing the above question, prompted by the Australian Carbohydrate Intolerance Study in Pregnant Women (ACHOIS),² which was abstracted in the same issue.³ The ACHOIS investigators compared a screen-and-treat programme for gestational diabetes with routine pregnancy care and used as their main end point a composite of 4 outcomes: shoulder dystocia, Duchenne-Erb palsy, fracture, and death—a natural choice given that a main purpose of gestational glycaemic control is to prevent the baby from being born too big. The topic is important and several points are worth noting.

Montori et al listed 3 questions to help decide the appropriateness of a composite outcome:

(a) Are the component …