Cluster randomized trials utilizing primary care electronic health records: methodological issues in design, conduct, and analysis (eCRT Study)

Table 4 Intraclass correlation coefficient (95% confidence interval) and correlation between pre- and post-intervention measures for the stroke trial

	Intraclass correlation coefficient (ICC) (95% confidence interval)		Correlation between outcome measures before and after intervention
	Before Intervention	After Intervention
Systolic blood pressure (mmHg)
All trial participants	0.026 (0.016 to 0.037)	0.022 (0.012 to 0.031)	0.43
Control trial arm	0.043 (0.021 to 0.066)	0.037 (0.018 to 0.057)	0.46
Intervention trial arm	0.010 (0.002 to 0.018)	0.008 (0.0005 to 0.015)	0.40
Diastolic blood pressure (mmHg)
All trial participants	0.023 (0.014 to 0.033)	0.016 (0.009 to 0.024)	0.42
Control trial arm	0.029 (0.013 to 0.046)	0.020 (0.008 to 0.033)	0.44
Intervention trial arm	0.018 (0.007 to 0.029)	0.013 (0.004 to 0.022)	0.40
Total serum cholesterol (mmol/L)
All trial participants	0.010 (0.004 to 0.016)	0.015 (0.007 to 0.022)	0.77
Control trial arm	0.015 (0.004 to 0.026)	0.019 (0.007 to 0.031)	0.76
Intervention trial arm	0.005 (0.000 to 0.012)	0.011 (0.003 to 0.020)	0.78

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