Vibration perception threshold: are multiple sites of testing superior to single site testing on diabetic foot examination?

Vibration perception threshold (VPT) values, measured at different anatomic locations on the foot and ankle, and the time to assess VPT and sensory perception using two difference modalities in 102 diabetic patients were compared. VPT was evaluated at the great toe, fifth metatarsal and ankle. Differences in VPT at these three sites, in addition to differences in duration of testing comparing single site (great toe) to multiple sites, and to standard SWMF testing were assessed. No significant difference in VPT between the great toe and fifth metatarsal was found for patients both with and without loss of protective sensation (LOPS). Mean VPT was significantly higher at the ankle compared with both the great toes and fifth metatarsals. However, the difference between ankle and great toe was not significant between patients with and without LOPS [3.9 +/- 11.2 (12%) vs. 3.0 +/- 10.8 (16%) volts, respectively, p > 0.6]. Testing of one site took approximately half the time of Semmes-Weinstein 10-gram monofilament wire SWMF testing (40.5 +/- 16.9 vs. 22.3 +/- 9.1 seconds, p < 0.01) and less than one third the time of three-site VPT testing (10.5 +/- 26.1 vs. 22.3 +/- 9.1 seconds, p < 0.01). There may not be a significant practical benefit in multiple site VPT testing when compared with single site testing on the great toe alone. The value of multiple site testing is further called into question when one notes that the great toe VPT remains the only site tested for sensitivity and specificity for ulceration.