Raised intracranial pressure and retinal haemorrhages in childhood encephalopathies: reply to the commentary by Squier.

Abstract

SIR–We would like to reply to the commentary by Squier on our paper.1, 2 This commentator considered there were two major concerns about our study: a failure to control for age and a problem of circularity bias resulting from retinal haemorrhages being involved in the diagnosis of inflicted traumatic brain injury (ITBI). As this was a prospective study which included children of all ages who presented with a traumatic or non-traumatic encephalopathy, the question of different ages was already addressed by the multiple logistic regression that we reported. The workings of our analyses were not shown in full because of constraints on the number of words, and only the significance of raised intracranial pressure (RICP) as a predictor of retinal haemorrhage adjusted for age and aetiological group was given. What we did not report was that in this analysis, aetiology also remained highly significant adjusted for the other two variables (p<0.001), while age was not in fact significant (see Table 1). This illustrates: (1) the tendency for ITBI cases to be younger but some overlap in age with the other two groups; (2) the general lack of a strong trend with age in each column; (3) the generally higher prevalence of retinal haemorrhage in cases with RICP, other things being equal; and (4) the generally higher prevalence of retinal haemorrhage in ITBI as compared to the other two aetiological groups, other things being equal. Essentially, this means that there is sufficient overlap in the age ranges of the three groups (and a sufficiently small trend with age) that we can continue to report a highly significant difference in retinal haemorrhage prevalence between ITBI and the other two groups even adjusting for age. With respect to the second issue raised by Squier in the commentary, circular reasoning is a potential problem for researchers in many clinical syndromes where there is no biochemical, genetic, or other specific investigation confirming the diagnosis. It has been minimized in our study by our diagnosis of ITBI which is not a single clinico-pathological entity and has different clinical features, reflecting different mechanisms of injury. In our study, there were nine different combinations of clinical features in the 21 ITBI cases, and this included three cases without retinal haemorrhages. Retinal haemorrhages were therefore not imperative for the diagnosis. Similarly, RICP was not a factor in making the diagnosis of ITBI. Any degree of circularity would not of course invalidate the other results about the relationship between RICP and retinal haemorrhage, which constitutes the bulk of this paper. Squier refers to the recent systematic review by the Swedish Agency for Health Technology Assessment on evidence for the ‘shaken baby syndrome’ which concluded that there is insufficient scientific evidence on which to assess the diagnostic accuracy of the triad in identifying traumatic shaking.3 It would have been pertinent to also mention the correspondence following its publication, from clinicians who have highlighted methodological flaws in that systematic review.4, 5 A provisional diagnosis of ITBI is made from the whole clinical picture – i.e. the relevant history, including ‘risk factors’, clinical examination, investigations and excluded differential diagnoses. Additionally, multi-agency professionals, with assured independence, attend a Child Protection Case Conference (CPCC) and provide further information about the past medical history, social history, and forensic details. A collective decision is made by the CPCC about what the likelihood is (i.e. probability), that the clinical presentation is due to an accidental cause, a non-accidental cause, or another cause. Doctors are guided by the GMC about their roles and responsibilities for child protection in CPCCs (www.gmcuk.org/guidance/ethical_guidance/13380.asp) and the decision of the CPCC is widely acknowledged as providing the most secure evidence of child abuse.