Head-to-head comparison of the WHO STEPwise approach with immediate unattended and delayed unattended automated blood pressure measurements during household-based screening: a diagnostic accuracy study in Lesotho

Abstract

Background: WHO introduced the STEPwise approach to surveillance (STEPS) to monitor trends in non-communicable diseases. For arterial hypertension, the STEPS protocol takes the average of the last two out of three standard blood pressure measurements (SBPM). This study assesses the diagnostic accuracy of SBPM, same-day and next-day unattended automated measurement (uABP), with 24 h ambulatory measurement (24 h-ABPM) as reference.

Methods: This diagnostic accuracy study was done within a population-based household survey on cardiovascular risk factors in two districts in Northern Lesotho. Adults (aged ≥ 18 years) with elevated SBPM (defined as ≥140/90 mmHg), and 2:1 age- and sex-matched participants with normal SBPM during the survey were recruited. Following SBPM, first uABP readings were obtained on survey day. Afterwards, participants received a 24 h-ABPM device. Second uABP readings were taken 24 h later, after retrieval of the 24 h-ABPM. The main outcome was overall diagnostic accuracy of all screening measurements (SBPM, first uABP, and second uABP), determined using area under the receiver operating characteristic curve (AUROC), with 24 h-ABPM as a reference.

Findings: Between November 2, 2021 and August 31, 2022, 275 participants (mean age 58 years (SD: 16 years), 163 (59%) female) were enrolled, 183 of whom had elevated and 92 had normal SBPM. Mean difference between systolic daytime 24 h-ABPM and screening measurements was highest for SBPM (mean difference: -13 mmHg; 95% CI: -14 to -11). Mean difference between diastolic daytime 24 h-ABPM and diastolic SBPM was -2 mmHg (95% CI: -4 to -1), whereas no difference was found for mean diastolic first uABP (mean difference: -1 mmHg; 95% CI: -2.0 to 0.3); and mean diastolic second uABP (mean difference: 1.0 mmHg; 95% CI: -0.4 to 2.3). White coat hypertension was highest with SBPM (55 [20%]), followed by first uABP (27 [9.8%]), and second uABP (18 [6.5%]). Using systolic daytime 24 h-ABPM as a reference, the uABPs had higher AUROC (first uABP: 87% [95% CI: 83-91]; second uABP: 88% [95% CI: 84-92]); SBPM: (79% [95% CI: 74-85]). This difference was significant between first uABP and SBPM (P = 0.0024), and between second uABP and SBPM (P = 0.0017).

Interpretation: uABP had better diagnostic performance than SBPM. Integration of uABP into STEPS protocol should be considered.

Funding: Swiss Agency for Development and Cooperation under the ComBaCaL project, and the World Diabetes Foundation.

Keywords: Ambulatory blood pressure monitor; Lesotho; STEPS; Sub-Saharan Africa; Survey screen blood pressure; Unattended automated office blood pressure.

Fig. 1

Study flow. SBPM = standard blood pressure measurement; 24 h-ABPM = 24 h ambulatory blood pressure monitor; BP = blood pressure; ∗Additional data between 01/09/2022 to 30/11/2022.

Fig. 2

Bland–Altman plots showing levels of agreement between the three screening measurements and daytime ambulatory blood pressure monitor (24 h-ABPM). (2a, 2c, 2e) Show daytime 24 h-ABPM systolic blood pressure (SBP) vs SBP of SBPM, 1st uABP and 2nd uABP, respectively. (2b, 2d, 2f) Show daytime 24 h-ABPM diastolic blood pressure (DBP) vs DBP of SBPM, 1st uABP and 2nd uABP, respectively. All values in mmHg. SBPM = standard blood pressure measurement; uABP = unattended blood pressure.

Fig. 3

Scatter plots of average 24-ABPM vs SBPM, 1st uABP and 2nd uABP. (a–c) Show average 24 h-ABPM SBP vs SBP of SBPM, 1st uABP and 2nd uABP respectively, using the cut off ≥140 mmHg. (d–f) Show average 24 h-ABPM DBP vs DBP of SBPM, 1st uABP and 2nd uABP respectively, using the cut off ≥90 mmHg. 24 h-ABPM = 24-h ambulatory blood pressure monitor; SBPM = standard blood pressure measurement; uABP = unattended blood pressure; SBP = systolic blood pressure; DBP = diastolic blood pressure. Black solid line is BP threshold for average 24 h-ABPM (130 mmHg systolic, 80 mmHg diastolic); dashed line is BP threshold for screening measurements (140 mmHg systolic, 90 mmHg diastolic). Green colour- BP measurements match gold standard. Orange colour-masked hypertension. Red colour-white coat hypertension.

Fig. 4

ROC curves using: (a) Systolic average 24 h-ABPM (≥130 mmHg) as reference vs systolic values of standard BP, 1st uABP, and 2nd uABP. P = 0.0011 for AUC difference between 1st uABP and standard BP; P = 0.047 for AUC difference between 2nd uABP and standard BP; P = 0.24 for AUC difference between 1st uABP and 2nd uABP; (b) Diastolic average 24 h-ABPM (≥80 mmHg) as reference vs diastolic values of standard BP, 1st uABP, and 2nd uABP. P = 0.45 for AUC difference between 1st uABP and standard BP; P = 0.066 for AUC difference between 2nd uABP and standard BP; P = 0.16 for AUC difference between 1st uABP and 2nd uABP; (c) systolic daytime 24 h-ABPM (≥135 mmHg) as reference vs systolic values of standard BP, 1st uABP, and 2nd uABP. P = 0.0024 for AUC difference between 1st uABP and standard BP; P = 0.0017 for AUC difference between 2nd uABP and standard BP; P = 0.56 for AUC difference between 1st uABP and 2nd uABP; (d) Diastolic daytime 24 h-ABPM (≥85 mmHg) as reference vs diastolic values of standard BP, 1st uABP, and 2nd uABP. P = 0.058 for AUC difference between 1st uABP and standard BP; P = 0.029 for AUC difference between 2nd uABP and standard BP; P = 0.49 for AUC difference between 1st uABP and 2nd uABP. ROC: receiver operating characteristics; AUC: area under the curve; uABP: unattended blood pressure; 24 h-ABPM: 24 h ambulatory blood pressure monitoring.