Quantitative assessment of diabetic peripheral neuropathy with use of the clanging tuning fork test.

OBJECTIVE

To describe the clanging tuning fork (CTF) test, a novel method for using the C 128-Hz tuning fork to test for diabetic peripheral neuropathy (DPN), to evaluate the accuracy and reproducibility of this technique, and to compare it with the 5.07 (10 g) Semmes-Weinstein monofilament test.

METHODS

To determine the mean and standard deviation for the CTF test, repeated measurements were taken on one toe of 12 patients with diabetes during one visit. After these tests, 30 randomly selected patients were tested on both feet, with right and left scores compared for reproducibility of the results. The scores of the CTF test were compared with the monofilament scores in 45 patients with diabetes. Presence of foot ulcers in 81 patients was correlated with both test scores.

RESULTS

The mean duration of vibration sensation was 10.2 seconds, with a standard deviation of +/-1.3 seconds. The Pearson correlation coefficient comparing the right and the left foot scores for the same patient was 0.947 (P<0.05). Among patients with 8 seconds or less of vibration perception, results of monofilament testing were abnormal only in those whose vibration perception was less than or equal to 4 seconds. Of 32 patients with vibration perception of 4 seconds or less, 50% had normal monofilament test scores, including 29% of 17 patients with absent vibratory sensation.

CONCLUSION

The CTF test is reproducible and accurate. It provides a quantitative assessment of DPN and can document severe neuropathy, even in the presence of a normal result with the 10-g monofilament test. The risk of foot ulcers, which is associated with diminished vibratory sensation, can therefore be detected earlier and more accurately with the CTF test. The CTF test should replace the 10-g monofilament test as the recommended technique for detection of DPN.