Long term monitoring in patients receiving treatment to lower blood pressure: analysis of data from placebo controlled randomised controlled trial.
OBJECTIVE
To determine the value of monitoring blood pressure by quantifying the probability that observed changes in blood pressure reflect true changes.


METHODS
Analysis of blood pressure measurements of patients in the perindopril protection against recurrent stroke study (PROGRESS).


METHODS
Randomised placebo controlled trial carried out in 172 centres in Asia, Australasia, and Europe.


METHODS
1709 patients with history of stroke or transient ischaemic attack randomised to fixed doses of perindopril and indapamide. Measurements Mean of two blood pressure measurements in patients receiving treatment recorded to the nearest 2 mm Hg with a standard mercury sphygmomanometer at baseline and then at three months, six months, nine months, and 15 months and then every six months to 33 months.


RESULTS
There was no change in the mean blood pressure of the cohort during the 33 month follow-up. Six months after blood pressure was stabilised on treatment, if systolic blood pressure was measured as having increased by >10 mm Hg, six of those measurements would be false positives for every true increase of >or=10 mm Hg. The corresponding value for an increase of 20 mm Hg was over 200. Values for 5 mm Hg and 10 mm Hg increases in diastolic blood pressure were 3.5 and 39, respectively. The likelihood that observed increases in blood pressure reflected true increases rose with the time between measurements such that the ratio of true positives to false positives reached parity at 21 months.


CONCLUSIONS
Usual clinical approaches to the monitoring of patients taking drugs to lower blood pressure have a low probability of yielding reliable information about true changes in blood pressure. Evidence based guidelines for monitoring treatment response are urgently required to guide clinical practice. Trial registration Australia and New Zealand Clinical Trial Registry.
Keenan
Katherine
K
Screening and Test Evaluation Program (STEP), School of Public Health, Building A27, University of Sydney, New South Wales 2006, Australia.
Hayen
Andrew
A
Neal
Bruce C
BC
Irwig
Les
L
D000959:Antihypertensive Agents / Q000627:therapeutic use*; D001794:Blood Pressure; D001795:Blood Pressure Determination; D003971:Diastole / Q000502:physiology; D005260:Female; D006801:Humans; D006973:Hypertension / Q000188:drug therapy* / Q000503:physiopathology; D007190:Indapamide / Q000627:therapeutic use*; D002546:Ischemic Attack, Transient / Q000503:physiopathology / Q000517:prevention & control*; D008134:Long-Term Care; D008297:Male; D008875:Middle Aged; D020913:Perindopril / Q000627:therapeutic use*; D055502:Secondary Prevention; D020521:Stroke / Q000503:physiopathology / Q000517:prevention & control*; D017211:Treatment Failure
D000959:Antihypertensive Agents; D007190:Indapamide; D020913:Perindopril