Peripheral arterial disease (PAD) is common, affecting about 20% of people over 60 years. The PAD confers a high cardiovascular risk and there is a need for an easy test to confirm its presence in the primary care so that appropriate specialist referral can be made. For many years, the ankle-brachial pressure index (ABPI) has been available as a first-line quantitative assessment of PAD. However, it has been unpopular due to concerns about its repeatability in a nonspecialist setting. In this issue, Ro et al describe a comparison continuous wave (CW) Doppler ultrasound with ABPI and photoplethysmography (PPG) in the detection of stenotic peripheral disease. They show that the sensitivity of ABPI is poor particularly in diagnosing the disease in the tibial segment and that an improvement in sensitivity is gained by performing CW Doppler together with ABPI and PPG. The ABPI has previously been shown to have good sensitivity and specificity compared to angiographic imaging. It is also readily available in the community in primary care with lowcost equipment. However, 2 important factors affect the quality of ABPI results. The first is the presence of calcified vessels seen in patients with diabetes, renal disease, and some elderly patients. This leads to underestimation of arterial disease through falsely high readings, as the calcified vessels are relatively incompressible. This can usually be recognized by a high ABPI score of >1.3. The second factor is the need to perform the test to a high standard using a clear protocol. Often, the failure to get reliable results has been due to poor training and performance of the test by relatively inexperienced health care professionals in primary care. The PPG is a low-cost, quick, and simple to do optical technique, but it is however seldom used in routine clinical assessments, largely because of a lack of normal reference ranges, uncertainties due to beat-to-beat variability in pulse characteristics and poorly applied quantitative analysis leading to subjective waveform interpretation. Allen and coworkers have employed systematic pulse wave analysis techniques to show that PPG at the great toe site has good sensitivity and specificity for PAD when compared to the ABPI reference. They provided evidence that normalized pulse shape and its deformity with disease ranks high as an accurate marker for the disease, followed closely second by exploiting bilateral timing differences between the toes. To achieve such confidence in the diagnostic performance of PPG for PAD detection, it has been established that beat-to-beat averaging of the pulse features was essential. Before other techniques for quantifying PAD are introduced there needs to be consideration of the sensitivity and specificity of the technique, ease of use, and the cost and training required to achieve reliable results. The question of training community carers is particularly pertinent, where the technique relies on interpreting waveform shapes rather than performing a protocol that gives a set of numbers that can be recorded. This would be the case with Doppler waveform and PPG techniques as described by Ro et al. Unless there is a very clear-cut distinction between significant and nonsignificant disease, the reliability and reproducibility are likely to be poor. In the case of Doppler waveform analysis, the cost, portability of equipment, and time taken to perform the measurements probably make this modality more suited to a referral center where a full duplex ultrasound can be performed giving both anatomical and hemodynamic information. The key factor in any screening technique is that all disease that warrants further assessment is picked up while recognizing those who clearly do not have significant disease, to avoid unnecessary referral. This implies a test with reasonable sensitivity and high specificity, so that those who definitely do not have disease are not referred unnecessarily. When performed outside a specialist center, it also implies a test that can be reliably performed by a range