What is the clinical evidence from this study?

Study design: Observational. Population: General population (Atherosclerosis Risk in Communities and Family Heart Study cohorts) (n=119). Intervention: Automated oscillometric ankle-brachial index (ABI) measurement vs. Repeat measurement. Primary outcome: Reliability coefficient for the ABI based on single ankle and arm systolic blood pressures (Reliability coefficient 0.61, 95% CI 0.50-0.70).

What does this research mean for the field?

The reliability coefficient for the ankle-brachial index based on single ankle and arm systolic blood pressures measured with an automated oscillometric device is 0.61, indicating a need for repeated measures in clinical practice to avoid diagnostic and therapeutic errors. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.NEUTRAL.

February 21, 2006Open Access

The reliability of the ankle-brachial index in the Atherosclerosis Risk in Communities (ARIC) study and the NHLBI Family Heart Study (FHS)

Key Result

The reliability coefficient for the ankle-brachial index based on single ankle and arm systolic blood pressures measured with an automated oscillometric device was 0.61.

Study Design

Type

Observational (n=119)

Multicenter

Yes

Structured PICO

Population

119 participants from the Atherosclerosis Risk in Communities (ARIC) study and the NHLBI Family Heart Study (FHS) who had repeat ankle-brachial index (ABI) measurements taken within 1 year. Mean age 61.0 years, 58.8% female, 84.0% white.

Intervention

Repeat ankle-brachial index (ABI) measurements using an automated oscillometric device (DINAMAP 1846 SX)

Outcome

Reliability coefficient (R) for the ankle systolic blood pressure, brachial systolic blood pressure, and ankle-brachial indexsurrogate

The moderate reliability of a single ABI measurement using an automated oscillometric device (R=0.61) highlights the need for repeated measures in clinical practice and when used as a predictor in regression models.

Main Result

Effect estimate: Reliability coefficient 0.61 (95% CI 0.50-0.70)

Limitations

Limited number of reliability study subjects in certain subgroups limited the ability to test for subgroup differences.
Estimates of within-person variation apply to the specific methodology used in these studies and may not apply to other situations or patient care settings.
The ABI was defined using ankle pressure measured in one randomly selected leg, preventing the assessment of how different measurement protocols affect reliability.

Abstract

BACKGROUND: A low ankle-brachial index (ABI) is associated with increased risk of coronary heart disease, stroke, and death. Regression model parameter estimates may be biased due to measurement error when the ABI is included as a predictor in regression models, but may be corrected if the reliability coefficient, R, is known. The R for the ABI computed from DINAMAP readings of the ankle and brachial SBP is not known. METHODS: A total of 119 participants in both the Atherosclerosis Risk in Communities (ARIC) study and the NHLBI Family Heart Study (FHS) had repeat ABIs taken within 1 year, using a common protocol, automated oscillometric blood pressure measurement devices, and technician pool. RESULTS: The estimated reliability coefficient for the ankle systolic blood pressure (SBP) was 0.68 (95% CI: 0.57, 0.77) and for the brachial SBP was 0.74 (95% CI: 0.62, 0.83). The reliability for the ABI based on single ankle and arm SBPs was 0.61 (95% CI: 0.50, 0.70) and the reliability of the ABI computed as the ratio of the average of two ankle SBPs to two arm SBPs was estimated from simulated data as 0.70. CONCLUSION: These reliability estimates may be used to obtain unbiased parameter estimates if the ABI is included in regression models. Our results suggest the need for repeated measures of the ABI in clinical practice, preferably within visits and also over time, before diagnosing peripheral artery disease and before making therapeutic decisions.

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