Arm Based on LEg blood pressures (ABLE-BP): Can leg blood pressure measurements predict brachial blood pressure? An individual participant data meta-analysis from the INTERPRESS-IPD Collaboration

Conference:

SAPC ASM 2021 - virtual

Talk Code:

1C.3

Presenter:

Sinead McDonagh

Twitter:

@Sinead1989, @INTERPRESS_IPD

Co-authors:

Sinead TJ McDonagh1, James Sheppard2, Fiona C Warren1, Kate Boddy1, Leon Farmer3, Helen Shore3, Phil Williams3, Philip S Lewis4, Rachel Baumber5, A Jayne Fordham6, Una Martin7, Victor Aboyans8, Christopher E Clark1

Author institutions:

1. University of Exeter Medical School, 2. University of Oxford, 3. Volunteer patient and public advisor, 4. Stockport NHS Foundation Trust, 5.Royal National Orthopaedic Hospital NHS Trust, 6. Mid Devon Medical Practice, 7. University of Birmingham, 8. Dupuytren University Hospital

Problem

Hypertension, a key modifiable risk factor for the prevention of stroke, is diagnosed and managed using blood pressures (BP) measured on the upper arm. Amputations, altered muscle tone after stroke or limb deformities can prevent accurate measurement of brachial BP, making decisions about appropriate treatment difficult. Leg BP measurement is advised as a practical alternative to brachial measurement, but limited data exist to guide clinicians’ interpretation of leg BP values in terms of hypertension diagnosis and treatment.Findings from our previous study-level systematic review and meta-analysis suggest that, on average, systolic BP is 17mmHg higher in the leg than the arm. However, substantial heterogeneity between contributing studies was found, limiting certainty about the applicability of this finding to individuals.Using BP data from the international Inter-arm BP difference individual participant data (INTERPRESS-IPD) Collaboration, we aimed to:1) Examine the relationship between arm and leg BP.2) Develop and validate a multivariable model predicting arm BP from leg BP.3) Investigate the prognostic role of leg BP in cardiovascular event and mortality risk prediction.

Approach

IPD meta-analyses using systolic arm and leg BP data available from 14 studies within the INTERPRESS-IPD Collaboration were undertaken. We explored cross-sectional relationships between arm and leg systolic BP using hierarchical linear regression with participants nested by study, in multivariable models. We predicted systolic arm BP using leg BP quantified using area under receiver operating characteristic (AUROC) curves. Prognostic models were also derived for all-cause and cardiovascular mortality, and cardiovascular events. Final models were validated using internal-external cross-validation analysis.

Findings

Arm and leg BP data were available for 33,710 individuals (mean age: 58.4 years, mean arm systolic/diastolic BP at baseline: 137.7/79.7mmHg, 44.7% female); 6,785 (20.1%) were current smokers, 20,191 (59.9%) had hypertension, 4,917 (14.6%) had diabetes and 5,797 (17.2%) had cardiovascular disease. Mean leg systolic BP was 12.0 mmHg (95% confidence interval, 8.8 to 15.2) higher than arm systolic BP. Descriptive modelling revealed systolic BP, female sex, smoking, total cholesterol, diabetes and ischaemic heart disease were associated with reduced arm-leg systolic BP differences (p<0.05). Age, body mass index and hypertension were associated with increased arm-leg systolic BP differences (p<0.05). Derivation cohort AUROC curves for predicted arm BP from leg BP reduced from 0.93 to 0.89 with each 5 mmHg reduction in BP from 160 to 130 mmHg. Further analyses are underway and will be presented at the conference.

Consequences

This is the first IPD meta-analysis to describe the relationship between arm and leg systolic BP using an international cohort. Our findings will support clinicians and patients to use leg BP measurements in detecting and managing hypertension and cardiovascular risk more effectively.

Submitted by:

Sinead McDonagh

Funding acknowledgement:

The INTERPRESS-IPD Collaboration was established with a grant from the NIHR Research for Patient Benefit programme (award/grant number: PB-PG-0215-36009). The ABLE-BP project is supported by the Stroke Association (award/grant number: SA PG 19/100043) and by the Thalidomide Trust (award/grant number: not applicable).