Fig. 1

Adjusted random effect estimates per centre for process indicators. This figure shows the between-centre differences for the process indicators (beware of different x-axes). Quality indicator definitions can be found in Additional file 3. On the y-axis, each dot represents a centre. A centre with an average indicator score has log odds 0 (a positive log odds indicates higher indicator scores and a negative log odds lower indicator scores). The between-centre differences are represented by the shape of the caterpillar plots; the variation in the log odds for individual centres and the corresponding confidence intervals (uncertainty). For example, the use of ICP monitoring shows large variation between centres with small confidence intervals, so there is high variation with low statistical uncertainty. While for use of low molecular weight heparin, the variation is large, but the statistical uncertainty is high as well (due to high adherence rates for most centres). The caterpillars were based on non-missing data (after imputation). ‘Use of Low Molecular Weight Heparin’ reflects the indicator ‘Number of patients that receive pharmaceutical prophylaxis with low molecular weight heparins/ total number of TBI patients admitted to the ICU’. ‘Surgery within 4 hours’ reflects the indicator ‘Median door-to-operation time for acute operation of SDH and EDH with surgical indication’. DVT deep venous thrombosis, EDH epidural hematoma, ICU intensive care unit, MOR median odds ratio, SDH subdural hematoma