The steel ball-bearing test: a new test for evaluating protective sensation in the diabetic foot

Aims/hypothesis The aim of the study was to assess a new steel ball-bearing test as a means of evaluating protective sensation in the diabetic foot. Methods Subjects were enrolled for this study as follows: (1) 39 patients (mean age 61.3±9.7 years) with neuropathy and prior neuropathic ulcer (Group A); (2) 36 patients (mean age 63.7±10.1 years) with neuropathy without neuropathic ulcer (Group B); (3) 34 patients (mean age 52.1±10.4 years) without neuropathy (Group C); and (4) 21 healthy volunteers (mean age 46.7±8.7 years) (Group D). Neuropathy was diagnosed by means of neuropathy disability score (NDS). The plantar area over the second metatarsal head of each foot was examined with steel ball-bearings of varying diameters. The smallest diameter that the patient could feel was used to define the ball-bearing score (range 1–6). Results A high ball-bearing score was significantly more frequent in patients with neuropathic ulceration than in neuropathic patients without ulceration and in diabetic patients without neuropathy (p<0.001). A high score was also more frequent in neuropathic patients without ulceration, than in patients without neuropathy (p<0.001). The ball-bearing score was significantly (p=0.01) correlated with the NDS, the monofilament test, the vibration perception threshold and the thermal perception threshold. The ball-bearing test had a sensitivity of 84% and a specificity of 100% for impaired protective sensation due to neuropathy, and a sensitivity of 84.6% and a specificity of 86.1% for detection of patients with prior neuropathic ulceration. Conclusions/interpretation The steel ball-bearing test has a high sensitivity and specificity both for the evaluation of protective sensation and for detection of patients with prior neuropathic ulceration.