The ALLHAT authors substantially underestimate the effect on outcome of the 3mm difference in systolic blood pressure that occurred between diuretic arm compared to ACE inhibitor arm.
Blood pressure studies comparing a combination of medications should ideally create treatment protocols where the medications are adjusted until the same blood pressure is achieved in each treatment arm of the trial, if possible. The 3 mm lower systolic blood pressure that was present with the diuretic treatment protocol strongly favored the diuretic initiated therapy.
The statistical manipulations and estimations used to correct for the differences in trial outcome resulting from this difference in blood pressure in the ALLHAT study are inaccurate.
The ALLHAT authors attempt to statistically correct for the difference in blood pressure between the groups and appear to have substantially underestimated the effects of creating blood treatment protocols that did not obtain the same levels of blood pressure control in their study.
The underestimation of the effect of the difference in systolic blood pressure on outcome is demonstrated in the ALLHAT authors' discussion of stroke rate in the black patients in the trial:
The ALLHAT investigators while discussing differences in stroke rate in black patients between diuretic and ACE inhibitor protocols in their initial 2002 report state that the 4mm difference in systolic blood pressure is not consistent "with the difference seen in black patients (13%-16% expected, 40% increase in stroke rate observed)."
Hence, the ALLHAT investigators are saying that the 4mm difference in systolic blood pressure for black patients for diuretic led therapy vs. ACE inhibitor led therapy explains only a 13-16% difference in stroke rate, not the 40% difference in stroke rate
There is no reason to accept the implication by the ALLHAT investigators that it is more reasonable to assume there are special protective properties in the diuretic beyond the well established efficacy of a diuretic on BP control in the black population.
ALLHAT's attempts to quantify the effects of the differences in blood pressure
between the 3 blood pressure treatment protocols on the trial outcome are
unreliable. To quote the ALLHAT investigators:
The estimation by the ALLHAT authors on the impact of the blood pressure differences on patient outcome for the different blood pressure regimens is inaccurate.