Diagnostic Performance of Blood Pressure Measurement Modalities in Living Kidney Donor Candidates

Abstract

Background and objectives: Precise BP measurement to exclude hypertension is critical in evaluating potential living kidney donors. Ambulatory BP monitoring is considered the gold standard method for diagnosing hypertension, but it is cumbersome to perform. We sought to determine whether lower BP cutoffs using office and automated BP would reduce the rate of missed hypertension in potential living donors.

Design, setting, participants, & measurements: We measured BP in 578 prospective donors using three modalities: (1) single office BP, (2) office automated BP (average of five consecutive automated readings separated by 1 minute), and (3) ambulatory BP. Daytime ambulatory BP was considered the gold standard for diagnosing hypertension. We assessed both the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC-7) and the American College of Cardiology/American Heart Association (ACC/AHA) definitions of hypertension in the cohort. Empirical thresholds of office BP and automated BP for the detection of ambulatory BP-diagnosed hypertension were derived using Youden index, which maximizes the sum of sensitivity and specificity and gives equal weight to false positive and false negative values.

Results: Hypertension was diagnosed in 90 (16%) prospective donors by JNC-7 criteria and 198 (34%) prospective donors by ACC/AHA criteria. Masked hypertension was found in 3% of the total cohort by JNC-7 using the combination of office or automated BP, and it was seen in 24% by ACC/AHA guidelines. Using Youden index, cutoffs were derived for both office and automated BP using JNC-7 (<123/82 and <120/78 mm Hg) and ACC/AHA (<119/79 and <116/76 mm Hg) definitions. Using these lower cutoffs, the sensitivity for detecting hypertension improved from 79% to 87% for JNC-7 and from 32% to 87% by ACC/AHA definition, with negative predictive values of 95% and 87%, respectively. Missed (masked) hypertension was reduced to 2% and 4% of the entire cohort by JNC-7and ACC/AHA, respectively.

Conclusions: The prevalence of hypertension was higher in living donor candidates using ACC/AHA compared JNC-7 definitions. Lower BP cutoffs in the clinic improved sensitivity and led to a low overall prevalence of missed hypertension in prospective living kidney donors.

Keywords: American Heart Association; Blood Pressure Determination; Blood Pressure Monitoring, Ambulatory; Living Donors; Masked Hypertension; Prospective Studies; blood pressure; hypertension; hypotension; kidney donation.

Graphical abstract

Figure 1.

Scatter plots for (A) office and (B) ambulatory systolic and diastolic BP (x axes) and corresponding ambulatory BP (y axes). Solid lines show the cutoffs for Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC-7) hypertension. Dashed lines show the cutoffs for American College of Cardiology/American Heart Association (ACC/AHA) hypertension.

Figure 2.

Bar graphs showing the proportions of donor candidates with sustained normotension, sustained hypertension (HTN), masked HTN, and white coat HTN using (A) Joint National Committee 7 and (B) American College of Cardiology/American Heart Association criteria for office BP, automated BP, and combined office and automated BP. The combined values indicate whether either office or automated BP was above the cutoff for HTN. The bar graphs in the right panel show the categories of BP using the optimal cutoffs described in Table 3 (A): (office BP <123/82 mm Hg; automated BP <120/78 mm Hg), and (B): (office BP <119/79 mm Hg; automated BP <116/76 mm Hg).

Figure 3.

Receiver operating characteristic curves showing the performance of office and automated BP. (A) The gold standard is on the basis of the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure guidelines for daytime ambulatory systolic BP ≥135 mm Hg or diastolic BP ≥85 mm Hg. (B) The gold standard is on the basis of the American College of Cardiology/American Heart Association guidelines for daytime ambulatory systolic BP ≥130 mm Hg or diastolic BP ≥80 mm Hg.