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Table 2 Quality assessment of included studies

From: The effectiveness of interventions to improve laboratory requesting patterns among primary care physicians: a systematic review

Author Intervention Design Independent of other changes Knowledge of allocated intervention Unlikely to affect data collection Shape of effect pre-specified Attrition bias Selective reporting Other risk of bias Overall risk
Horn et al. [17] Changing order form ITS Low risk High risk Low risk Low risk Unclear risk Low risk Low risk High risk
    The study had a control group Participants knew which intervention they were receiving Sources and data collection methods same before and after intervention Specified Missing data unclear Appropriate outcomes reported No other potential bias  
Author Intervention Design Random sequence generation Allocation concealment Protection against contamination Blinding Attrition bias Selective reporting Similar at baseline Overall risk
Shalev et al. [27] Changing order form CBA High risk High risk N/A High risk Low risk Low risk N/A High risk
    CBA study CBA study No control group No blinding No missing data Appropriate outcomes reported No control group  
Kahan et al. [26] Changing order form CBA High risk High risk N/A High risk Low risk Low risk N/A High risk
    CBA study CBA study No control group No blinding No missing data Appropriate outcomes reported No control group  
Zaat et al. [28] Changing order form CBA High risk High risk Unclear risk High risk Low risk Low risk Unclear risk High risk
    CBA study CBA study No information in text Participants knew what they had been allocated to No missing data Appropriate outcomes reported No information in text on baseline characteristics, baseline outcomes similar (Fig 1/2)  
Baricchi et al. [25] Education CBA High risk High risk Unclear risk High risk Low risk Low risk Unclear risk High risk
    CBA study CBA study No information in text Participants knew what they had been allocated to No missing data Appropriate outcomes reported No information in text  
Larson et al. [18] Education CBA High risk High risk Unclear risk High risk Low risk Low risk Unclear risk High risk
    CBA study CBA study No information in text Participants knew what they had been allocated to No missing data Appropriate outcomes reported No information in text  
Verstappen et al. [21] Education RCT Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk
    Blocked randomization Cluster trial, allocation after recruitment completed Independent clinics Controls were blinded, hence preventing the Hawthorne effect No missing data Appropriate outcomes reported Outcomes measured at baseline and baseline characteristics reported and similar  
van Wijk et al. [22] Guidelines RCT Low risk Low risk Low risk High risk Low risk Low risk Low risk High risk
    “researcher not involved in the study…performed the randomisation using random-numbers table” “each practice assigned by simple random allocation” Separate practices All participants knew what they had been allocated to. Test ordering in controls may have been affected Missing data similar between groups and all participants accounted for Appropriate outcomes reported Similar baseline characteristics  
Baker et al. [23] Guidelines and feedback RCT Low risk Low risk Low risk High risk Low risk Low risk High risk High risk
    Random number table Cluster trial, allocation after recruitment completed Primary care physicians work separately Participants knew what they had been allocated to. Test ordering in controls may have been affected No sites lost to follow-up Appropriate outcomes reported Participants in group 2 had fewer patients and GPs than group 1  
Thomas et al.[19] Feedback and education Cluster RCT Low risk Low risk Low risk High risk Low risk Low risk Low risk High risk
    “cluster randomization…with a minimization procedure” Cluster trial, allocation after recruitment completed. Separate practices Participants knew what they had been allocated to. Test ordering in controls may have been affected. No missing data Appropriate outcomes reported Similar baseline characteristics  
Tomlin et al. [24] Guidelines, feedback and Education CBA High risk High risk High risk High risk Low risk Low risk High risk High risk
    CBA study CBA study “Changes…might be explained by ….contamination of the comparison group” Participants knew what they had been allocated to. Test ordering in controls may have been affected No missing data Appropriate outcomes reported Intervention group included GPs only while control group included locum GPs also