Evaluating alternative methods of comparing antihypertensive treatment intensity

Abstract

Objectives: To change blood pressure treatment, clinicians can modify medication count or dose. However, existing studies have measured count modification, which may miss clinically important dose change in the absence of count change. This research demonstrates how dose modification captures more information about management than medication count alone.

Study design: Retrospective cohort study.

Methods: We included patients 65 years and older with established primary care at the Veterans Health Administration (July 2011-June 2013). We captured medication count and standardized dose change over 90 to 120 days using a validated pharmacy fill algorithm. We determined frequency of dose change without count change (and vice versa), no change in either, change in same direction ("concordant"), and change in opposite direction ("discordant"). We compared change according to systolic blood pressure (SBP) and compared concordance using a minimum threshold definition of dose change of at least 50% (instead of any change) of baseline dose modification.

Results: Among 440,801 patients, 64.2% had dose change; 22.0%, count change; 35.6%, no change in either; 42.4%, dose change without count modification; and 0.2%, count change without dose modification. Discordance occurred in 2.1% of observations. Using the minimum threshold definition of change, 68.7% had no change in either dose or count. Treatment was more frequently changed at SBP greater than 140 mm Hg.

Conclusions: Measuring change in antihypertensive treatment using medication count frequently missed an isolated dose change in treatment modification and less often misclassified regimen modifications where there was no modification in total dose. In future research, measuring dose modification using our new algorithm would capture change in hypertension treatment intensity more precisely than current methods.

Figure 1.

Proportions of changes for each possible combination of dose and medication count modification, according to intensity of dose change to define treatment modification, visit intervals (N=440,801 patients for 90–120 days, and N=499,207 patients for 365–395 days), and baseline SBP. The figure displays the proportions of change for each possible combination of dose change (or no change) and medication count change (or no change). No change was defined as no change in either medication dose or count. A concordant change was defined as a dose and medication count change in the same direction. A discordant change was defined as a dose increase with medication count reduction, or a dose decrease with medication count increase. “Dose change only” refers to a dose change without any medication count modification. “Medication count change only” refers to a medication count change without dose modification (or with dose modification <25% or <50% of baseline dose for the second and third columns of the first panel). Abbreviations: N, number; SBP, systolic blood pressure.