Incidence of hospital admission does not equal incidence of disease

doi:10.1136/bmj.320.7244.1277

From trainee to consultant, BMJ Group offers doctors around the world tailored information, special events, learning resources and recruitment services at every step along their career path.

... by doctors, for doctors, for patients
We are open for entries!

Online learning

BMJ Learning

High-quality CME / CPD for doctors and other healthcare professionals. BMJ Learning features hundreds of accredited, peer-reviewed learning modules in text, video, and audio formats. Find out more

Courses and Qualifications

BMJ Masterclasses

BMJ Masterclasses, led by experts, help clinicians to use the latest evidence and recent guidelines in practice and meet their CPD/CME requirements. Find out more

Exam Preparation

The leading provider of online exam preparation, helping over 167,000 healthcare professionals to pass their exams. Find out more

onExamination

Search all BMJ comment articles:

From

Limit by

Access to the full text of this article requires a subscription or payment. Please log in or subscribe below.

Conclusions drawn from data are incorrect

Louis H Pobereskin, consultant neurosurgeon (louis.pobereskin@phnt.swest.nhs.uk),
J Robert Sneyd, consultant anaesthetist

Derriford Hospital, Plymouth PL6 8DH
Epidemiology, Institute of Public Health, Odense University, University of Southern Denmark, DK 5000 Odense C, Denmark
Department of Biostatistics, University of Aarhus, DK 8000 Aarhus, Denmark
Department of Neurology, Odense University Hospital, Odense, Denmark
Danish Epidemiology Science Centre, University of Aarhus, DK 8000 Aarhus, Denmark
Department of Clinical Epidemiology of Aarhus and Aalborg University Hospitals at the Institute of Epidemiology and Social Medicine, University of Aarhus, DK 8000 Aarhus, Denmark

EDITOR—We are concerned about Gaist and colleagues' methods and feel that the conclusions they draw from their data are incorrect.1

The diagnosis of subarachnoid haemorrhage was validated in a sample from only one county. Is Funen County representative of Denmark, and how was it selected? Hospitals with 10 or fewer registered patients in the study period were excluded. Why was it appropriate to exclude the smaller hospitals when they may be a source of patients with particularly low predictive value for a registered diagnosis of subarachnoid haemorrhage?

The cohort of first degree relatives was overwhelmingly made up of children, and theywere the only group in table 2 for whom the incidence rate ratios were significantly different from 1 The main problem with the study is one that plagues much of the literatureon subarachnoid haemorrhage—it was hospital based. The strongest predictor of survival in subarachnoid haemorrhage is age. This is just …