Author's response

Hasse Melbye

We wanted to demonstrate the natural course of the C-reactive protein (CRP) response during viral respiratory infections, and none of the patients described in our study were treated with antibiotics.

Our material is, as van der Wouden et al comment on, not sufficiently representative of the upper respiratory tract infections we meet in general practice. The most severe viral infections may have been excluded, and we know from previous studies that CRP values above 100 mg/l may be found in influenza and adenovirus infections.1 I agree with van der Wouden et al that more systematic research is needed in this field. However, some useful information may be obtained from our study.

The CRP response in viral respiratory infections has some typical features. The maximum CRP value is reached when the illness has lasted 2–4 days, and falls rapidly over the following days. Values below 10 mg/l is the rule after 7–10 days in uncomplicated cases. These features have also been indicated by other studies.2^,3 This knowledge can be taken into consideration when results of the CRP test are interpreted in patients with acute cough or a flu-like illness.

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