This means that the distribution of patients Z-VAD-FMK chemical structure over the various contexts is at least partly selective in character. This is reflected in the actual risk profiles of the distinct context related patient groups (figure 2). It is plausible that a high percentage of patients at higher actual risk

(in the absence of professional intervention) correlates with a high relative incidence of adverse outcomes. This implies that the same actual risks that influence the choice of the professional organisational context also influence the incidence of adverse outcomes in the related patient group. Hence, a professional organisational context-category cannot be considered as an independent determinant. It is important to note that the risk profile of a context related patient group can also be affected

by the exclusion of patients (records) because of the design of a study. Figure 2 Factors influencing the relative incidence of adverse outcomes in context related patient groups. Distribution of deliveries over the 24 h day The distribution of patients (records) over the distinct context-categories is not only determined by professional choices. This is especially true for patients with a spontaneous onset of labour (ie, without professional intervention). We base this claim on a twofold assumption: (1) Under natural conditions the deliveries are randomly spread and, therefore, in a population of sufficient size, (approximately) equally distributed over the 24 h day; (2) Under these conditions, the actual and potential risks in this population are also (approximately) equally distributed over the 24 h day. The reverse side of this basic assumption is that, in case of an unequal distribution of deliveries, we cannot assume that the

risks are equally distributed over those 24 h.12 In this way we therefore ignore the smaller peaks and troughs in the distribution of births over the day that have been described.13 14 A responsible comparison of context-categories If the objective is to gain insight into the performance of a professional organisational context-category, GSK-3 the conventional method is to compare the (adverse) outcomes of births in the related patient group (transversal) with those in a reference category.5–10 To complicate matters, the relative incidence of adverse outcomes in a context related patient group is not only affected by contextual factors, but also by patient-related factors (figure 2). A difference in the incidence of adverse outcomes between two context related patient groups can therefore only be attributed (exclusively) to a difference in performance of the relevant professional organisational contexts if it can be established that this difference in incidence is not caused by a difference in actual risk profiles.