Blood pressure during blood collection and the implication for absolute cardiovascular risk assessment

Background: Blood collection and blood pressure (BP) measurements are routinely performed during the same consultation to assess absolute cardiovascular disease (CVD) risk. This study aimed to determine the effect of blood collection on BP and subsequent calculation of the absolute CVD risk.

Methods: Forty-five participants aged 58 ± 9 years (53% male) had systolic BP (SBP) measured using clinical guideline methods (clinic SBP). Then, on a separate visit, BP was measured immediately before, during, and after blood collection. Absolute CVD risk scores were calculated (Framingham equation) using SBP from each measurement condition and compared.

Results: The prevalence of low (<10%), moderate (10-15%), and high (≥15%) absolute CVD risks among the participants was 67%, 22%, and 11%, respectively, using clinic SBP. SBP values before and during blood collection were significantly higher compared to values after blood collection (130 ± 18 and 132 ± 19 vs. 126 ± 18 mm Hg; p = 0.010 and p = 0.003, respectively). However, there were no significant differences between clinic SBP (128 ± 18 mm Hg) and blood collection SBP (p = 0.99) or the absolute CVD risk scores (7.3 ± 6.5; 7.6 ± 5.9; 7.7 ± 6.1; and 7.1 ± 5.7%, respectively; p = 0.995 for all). The mean intraclass correlation (95% CI) indicated good agreement between absolute CVD risk scores calculated with clinic SBP and each blood collection SBP (0.86 [95% CI 0.74-0.92], 0.85 [95% CI 0.71-0.91], and 0.87 [95% CI 0.76-0.93], respectively; p < 0.001, for all).

Conclusion: Absolute CVD risk calculation is not affected by use of SBP measurements recorded at the time of blood collection. Therefore, it is acceptable to collect blood and measure BP during the same consultation for absolute CVD risk assessment.