USPSTF Finds Insufficient Evidence for ABI Screening

September 3, 2013—The United States Preventive Services Task Force (USPSTF) has issued an updated recommendation statement on screening for peripheral artery disease (PAD) and cardiovascular disease (CVD) risk assessment via ankle–brachial index (ABI) in adults. Virginia A. Moyer, MD, et al published the statement in the Annals of Internal Medicine (2013;159:342–348).

In this update of the 2005 recommendation, the USPSTF concluded that the current evidence is insufficient to assess the balance of benefits and harms of screening for PAD and CVD risk assessment with ABI in adults. This recommendation applies to asymptomatic adults who do not have a known diagnosis of PAD, CVD, severe chronic kidney disease, or diabetes.

As summarized in the Annals of Internal Medicine, the USPSTF reviewed the evidence on the use of resting ABI as a screening test for PAD or as a risk predictor for CVD. The review focused on resting ABI as the sole screening method; the diagnostic performance of ABI testing in primary care populations, unselected populations, and asymptomatic populations; the predictive value of ABI testing for major CVD outcomes in primary care or unselected populations; and the effect of treatment on general CVD and PAD-specific morbidity in patients with asymptomatic or minimally symptomatic PAD.

The USPSTF advised that it makes recommendations about the effectiveness of specific preventive care services for patients without related signs or symptoms. These recommendations are based on the evidence of both the benefits and harms of the service and an assessment of the balance. The USPSTF does not consider the costs of providing a service in this assessment.

The task force stated that it recognizes that clinical decisions involve more considerations than evidence alone and that clinicians should understand the evidence but individualize decision making to the specific patient or situation. Similarly, the USPSTF noted that policy and coverage decisions involve considerations in addition to the evidence of clinical benefit and harm.

The systematic evidence review of ABI for PAD screening and CVD prediction among asymptomatic adults was published by Jennifer S. Lin, MD, et al in the Annals of Internal Medicine (2013;159:333-341).

The investigators concluded that adding ABI to the Framingham risk score (FRS) probably has limited value for predicting coronary artery disease (CAD) or CVD. Treatment benefits for asymptomatic individuals with screen-detected PAD have not been established.

As summarized in the Annals of Internal Medicine, the investigators sought to review the evidence on the ability of ABI to predict CVD morbidity and mortality independent of FRS factors in asymptomatic adults and on the pros and cons of treating screen-detected adults with PAD. They used data from MEDLINE and the Cochrane Central Register of Controlled Trials (1996–2012), clinical trial registries, reference lists, and experts. The investigators analyzed English-language, population-based prognostic studies evaluating ABI in addition to FRS and treatment trials or studies on the harm of treatment in screen-detected adults with PAD. They extracted data on dual quality assessment and abstraction of relevant study details.

The investigators reported that one large meta-analysis (n = 43,919) showed that ABI could reclassify the 10-year risk for CAD, but it did not report measures of appropriate reclassification (the net reclassification improvement [NRI]). Four heterogeneous risk-prediction studies showed that the magnitude of the NRI was probably small when ABI was added to FRS to predict CAD or CVD events. Of two treatment trials meeting inclusion criteria, one large trial (n = 3,350) showed that low-dose aspirin did not prevent CVD events in patients with screen-detected low ABIs but may have increased the risk of major bleeding events.

Addressing limitations of this analysis, the investigators noted that most prognostic studies did not allow for calculation of a bias-corrected NRI. Also, evidence on treatment benefits and harms was limited to aspirin and was scant.