Editor,—We read with interest the paper by Dr Hardie and colleagues.¹ We all agree now on the non-specificity of the case definition and on the heterogeneous nature of Reye’s syndrome.^2–4 Updated Reye’s syndrome is not a specific clinicopathological entity, but a descriptive term used to designate the condition of a child presenting with an unexplained non-inflammatory encephalopathy and signs of liver dysfunction (international workshop ‘Reye’s syndrome revisited’, Leuven, 3 May 1996).

However, as there is a wide spectrum of differential diagnoses in patients meeting the diagnostic criteria,⁵ classifying them now in two groups, the ‘Reye group’ and the ‘Reye-like inherited metabolic disease group’ is inaccurate: the Reye group again is heterogeneous, composed of patients with infections (and fever), and of patients with toxic and other diseases. This classification again enhances the risk of epidemiological biases^1–3.

Whether the scoring system devised by the authors is a valid predictor of ‘Reye’ (high score) versus ‘Reye-like’ (low score) has to be challenged as well. This scoring system does include exclusion criteria for Reye’s syndrome (for example a patient with positive cerebrospinal fluid can still be diagnosed as having …