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Table 3 Overview of key characteristics of the stepped wedge design

From: The impact of the HEART risk score in the early assessment of patients with acute chest pain: design of a stepped wedge, cluster randomised trial

(i) →

Stepped wedge design has features of cluster randomisation, i.e. during a specific time period only type of intervention (usual care or HEART score) is administered

       a. →

This reduces the risk of contamination

       b. →

The effect of clustering needs to be taken into account in the statistical analysis

(ii) →

Stepped wedge design has features of a one direction cross-over trial, i.e. each hospital contributes data from both usual care and HEART score in a fixed order.

       a. →

Allows for comparison of results within hospitals which may be less confounded by differences in case mix than between hospitals

       b. →

The fixed order from usual care to HEART score further reduces the risk of contamination as the HEART score is relatively simple to calculate.

       c. →

Due to the cross-over, each hospital will provide data about the (problems in) implementation of the HEART score

(iii) →

Switch from usual care to HEART score in hospitals is evenly and randomly distributed over calendar time

       a. →

This reduces the impact of potential changes over time in other factors than the intervention

       b. →

It facilitates the close monitoring and logistic of all activities surrounding the switch

(iv) →

Gradual implementation of new strategy is carried out, thereby providing data about the process itself.