A post-hoc analysis of the Australian National Blood Pressure Study has confirmed that a treatment strategy based on absolute risk is superior to treatment based on BP level alone.
Researchers at the Menzies Institute for Medical Research in Tasmania reviewed data from the chlorothiazide trial carried out in the 1970s in 3244 participants and found those with low absolute risk gained little benefit from antihypertensive therapy, regardless of BP levels.
In contrast, patients with a high absolute risk at entry to the trial showed substantial benefits of antihypertensive treatment, according to the analysis published in BMJ Open.
The trial involved middle-aged people (35-69 years) with an overall moderate five year cardiovascular risk of 10.5%, with moderately elevated BP (mean 159/103mmHg).
In the re-analysis, the subgroup of patients with a high risk (>17%) showed significant benefits from antihypertensive treatment, equivalent to a number needed to treat of 23 to prevent one major cardiovascular event, 18 to prevent any event, and 45 to prevent death from any cause.
In contrast, there was no significant benefit from antihypertensive treatment in the low (<6.1%) or medium (6.1%-17%) risk subgroups of patients.
For low risk patients the number needed to treat with an antihypertensive to prevent one cardiovascular event was 476, and for medium risk patients the number was 164.
“Our analysis confirms that the benefit of treatment was substantial only in the high-risk tertile, reaffirming the rationale of treating elevated blood pressure in the setting of all risk factors rather than in isolation,” concluded the researchers, including Professor Mark Nelson,Senior Professorial Fellow at the Institute.
A similar conclusion was drawn by international researchers who conducted an analysis of 11 antihypertensive trials with 47,872 participants.
It found that a treatment strategy based on predicted cardiovascularrisk could prevent more events and require treatment of fewer persons than one based on SBP level.
Compared with treating everyone with SBP ≥ 150 mmHg, a treatment strategy based on absolute risk would require treatment of 29% fewer people to prevent the same number of events, it found.
This approach would prevent 16% more events for the same number of persons treated, the analysis in PLOS Medicine concluded.
“Our results support the principle that treatment decisions that are based on absolute cardiovascular risk compared with blood pressure alone are superior for identifying persons with the highest expected benefit from blood pressure-lowering treatment, especially in primary prevention.