Using thresholds based on risk of cardiovascular disease to target treatment for hypertension: modelling events averted and number treated

Objective To estimate the impact of using thresholds based on absolute risk of cardiovascular disease to target drug treatment to lower blood pressure in the community. Design Modelling of three thresholds of treatment for hypertension based on the absolute risk of cardiovascular disease. 5 year risk of disease was estimated for each participant using an equation to predict risk. Net predicted impact of the thresholds on the number of people treated and the number of disease events averted over 5 years was calculated Setting Auckland, New Zealand. Participants 2158 men and women aged 35-79 veers randomly sampled from the general electoral rolls. Main outcome measures Predicted 5 year risk of cardiovascular disease event estimated number of people for whom treatment would be recommended and disease events averted over 5 years at different treatment thresholds. Results 46 374 (12%) Auckland residents aged 35-79 receive drug treatment to lower their blood pressure, averting an estimated 1689 disease events: over 5 years. Restricting treatment to individuals with blood pressure greater than or equal to 170/100 mm Hg and those with blood pressure between 150/90-169/99 mm Hg who have a predicted 5 year risk of disease greater than or equal to 10% would increase the net number for whom treatment would be recommended by 19 401. This 42% relative increase is predicted to avert 1139/1689 (68%) additional disease events overall over 5 years compared with current treatment. If the threshold for 5 year risk of disease is set at 15% the number recommended for treatment increases by < 10% but about 620/1689 (37%) additional events can be averted. A 20% threshold decreases the net number of patients recommended fur treatment by about 10% but averts 204/1689 (12%) more disease events than current treatment. Conclusions Implementing treatment guidelines that use treatment thresholds based on absolute risk could significantly improve the efficiency of drug treatment to lower blood pressure in primary care.