30 Two investigators (BMW and SD) also kept detailed notes during each meeting documenting how the team arrived at decisions regarding various categories of contributing factors, which they could refer to when review team members disagreed on categorisation of contributing factors, further improving the consistency of our process.
We also changed the categorisation of economic factors in the framework.
Secondly, we could not internally validate the IGCC classification, because the exact steps taken in the modelling process (selection and categorisation of risk factors) were not defined.
For example, the influences of family and the media were present at both of these stages, but the categorisation of these factors was re-specified in the new model.
(b) Primary research which either specifically aimed to identify the contributory factors (often referred to as 'causes' within studies) of active failures or threats to patient safety, or reported a clear framework for the categorisation of contributory factors of errors or threats to patient safety in the results section.
50 Thirdly, arbitrary or "data dredging" categorisation of continuous factors and continuous outcomes can easily bias findings toward a significant result, particularly if analyses are repeated for multiple cut-offs until a categorisation is found that provides the most significant P value.
Given that the categorisation of rheumatoid factor was devised to maximise the relation between rheumatoid factor and rheumatoid arthritis, the risk estimates based on these categories could be exaggerated and need to be replicated in another study.
Although many ICU studies have focused on AI categorisation and examination of factors immediately preceding the AI, few have investigated the potential contribution from latent or hidden factors (e.g. poor staff supervision).
One important reason for this concerns the inadequate use of statistical methods for continuous predictors, such as age or haemoglobin, finally leading to difficulties in comparing multivariable models with different categorisations of the factors (Simon and Altman, 1994).
In general, comparison between studies is limited owing to differences in categorisation of the prognostic factors.
