Critical evaluation of stress testing in the diagnosis of peripheral vascular disease.

We studied 218 patients (372 limbs) and 25 normal subjects (50 limbs) with resting ankle index (RAI), treadmill exercise (TE), and postocclusive reactive hyperemia (PORH) to determine whether diagnostic accuracy is improved through the use of stress testing. In addition, we studied 10 patients with stable claudication (20 limbs) to determine the reproducibility of the three measures. RAI was the most reproducible measure, with the smallest variance between testing days (P less than 0.001). RAI differentiated between arteriographically diseased and normal limbs with a sensitivity of 97% and a specificity of 100%, whereas the corresponding values for TE were 97% and 96% and for PORH 89% and 96%. Recovery to baseline index was prolonged in the diseased group compared with normal (p less than 0.001 for both TE and PORH), but this was of limited discriminative value. Receiver-operating characteristic curve analysis documented that RAI was as diagnostically useful as TE and that both were more valuable than PORH (P less than 0.02). However, the routine addition of stress testing increased diagnostic yield by only 1.6% and cost $1100 for each limb correctly diagnosed through the addition of stress testing. RAI is a simple, accurate, and reproducible test. Routine stress testing is not cost effective, adding little diagnostic information to RAI, and it should be reserved for the small subset of symptomatic patients with normal RAI.