Is blood pressure reduction a valid surrogate endpoint for stroke prevention? an analysis incorporating a systematic review of randomised controlled trials, a by-trial weighted errors-in-variables regression, the surrogate threshold effect (STE) and the biomarker-surrogacy (BioSurrogate) evaluation schema (BSES)

Table 3 Weighted ordinary least squares errors-in-variables regression of stroke relative risk reduction and systolic and diastolic blood pressure difference respectively, assuming 0.9, 0.8, 0.7 and 0.6 reliability coefficients for estimated blood pressure difference

Reliability coefficient	Regression Slope	Regression Slope p-value	R²	STE*	STEP**
	Systolic Blood Pressure
1.0	0.0196	0.010	0.37	7.4	64%
0.9	0.0217	0.008	0.41	7.1	66%
0.8	0.0245	0.006	0.46	6.7	68%
0.7	0.0280	0.004	0.52	6.3	70%
0.6	0.0327	0.002	0.61	5.9	72%
		Diastolic Blood Pressure
1.0	0.0453	0.000	0.58	2.6	76%
0.9	0.0503	0.000	0.64	2.4	78%
0.8	0.0566	0.000	0.72	2.2	80%
0.7	0.0647	0.000	0.83	1.9	83%
0.6	0.0755	0.000	0.96	1.2	88%

ISSN: 1471-2288