Infection developing in the intensive care unit is a common complication of critical illness, but notoriously difficult to diagnose. A definite diagnosis based on the most reliable tests usually is not possible for at least two days. It is unclear what the optimal management approach should be while awaiting the results of diagnostic tests. In some circumstances, broad spectrum antibiotics are started with a plan to adjust them once the results of cultures are available. Observational studies show that this results in greater antibiotic use, and the risk of superinfection and resistance. In other circumstances, antibiotics may be withheld pending the results of cultures, a strategy that leads to a delay in therapy when cultures are positive, and that may be associated with a worse clinical outcome.

We undertook a randomized pilot study to address the question: "In a critically ill patient for whom clinicians are uncertain whether infection may be present, and in whom potential sites of infection have been managed by removing or changing invasive devices, can a policy of delaying antibiotic treatment until cultures are available reduce the risks of excessive antibiotic use, without increasing the risks associated with delayed therapy?"

Recognizing that the question has not been formally addressed before, and that approaches to clinical management are both widely divergent and passionately held, our pilot study tested the feasibility and acceptability of undertaking a larger trial with sufficient power to determine equivalence.