This rate is remarkably stable and consistent across studies using prospective criteria or retrospective selection.
Our prospective criteria are the same as the retrospective criteria except that we do not consider length of stay.
Limitations of cohort analyses like that of Rana and colleagues include the lack of prospective criteria for initiation of NIV and intubation in the face of NIV failure.
Data extracted from each eligible study included first author; year of publication; participants' age, sex, and nationality (which was further classified in Asian and non-Asian groups); study type (cross-sectional, prospective); criteria used for defining primary outcomes; and exposure cutoffs.
Although lack of active UC on histological analysis should, ideally, have been a prospective exclusion criterion, histology could only be assessed practically after study initiation due to the lengthy time required for central analysis.
Another limitation is that children were not classified into a specific Rome III functional gastrointestinal disorder (e.g. irritable bowel syndrome vs. functional dyspepsia), though recent studies suggest this may be difficult to do even with prospective standardized criteria [ 17].
An artificial start date was defined for 31 March 2008 to allow sufficient time for the application of prospective exclusion criteria, such as 'clinically significant gastrointestional bleeding within 6 months of randomisation'.
The prospective exclusion criteria were pregnancy, renal insufficiency (defined as serum creatine levels ≥1.5 mg/dL), anaemia (haematocrit <30%), platelet count <100 000/µL, major bleeding, any gastrointestinal bleeding, trauma or the inability to provide informed consent for any reason.
For example, the prospective and arbitrary criterion used in our analysis (the 90th centile of closure times for all patients enrolled in the study) discerned an arguably modest 12.4% of patients with a diagnosis of non-cardiac symptoms.
Diagnosis of septic shock was prospective and used standard criteria similar to those used in most clinical trials in this clinical setting.
