We were grateful to a number of people who contacted us about our article on how to use C reactive protein (CRP).1

Abelian from Wrexham Maelor Hospital drew our attention to data on plasma half-life, suggesting this was 19 hours in an adult2 rather than the previously quoted 4–7 hours.3 4

Emmerson asked if there were robust data in support of the range of non-infectious conditions quoted to cause a rise in CRP in the newborn period. Our article had quoted a review by Hengst.5 We therefore reviewed the papers referenced in this review. Chiesa et al6 showed that mean CRP concentration at birth was increased by a factor of 1.50 (95% CI 1.32 to 2.03) if the 5-minute Apgar score was <8 and by a factor of 1.32 (95% CI …