Diagnostic prediction rules are tools to assist clinical decision making and aim to either improve patients’ health or provide other benefits without adversely affecting patients. However their uptake in clinical practice has been limited. Possible explanations include uncertainty about their performance compared to and in combination with clinicians’ clinical judgment and complexity for use at the bedside. In terms of diagnostic performance, existing diagnostic prediction rules do not clearly outperform the judgment of clinicians. However, they may improve patient health and process outcomes in some clinical conditions. C-reactive protein provides useful diagnostic information for children with suspected bacterial infection. Simplification reduced the performance of one diagnostic prediction rule with acceptability of this context dependent.