Vibration perception threshold testing in patients with diabetic neuropathy: ceiling effects and reliability

Aims To test the reliability of a new vibrometer (Maxivibrometer) which was constructed so that vibration perception threshold (VPT) could be determin ed without the disadvantage of the off-scale measurements frequently experi enced with the Biothesiometer. Methods The two devices were compared and tested on a group of diabetic neu ropathic subjects and a group of healthy, matched control subjects. VPT was tested on the plantar surface of the feet. Result The Maxivibrometer gave an actual measurement in all cases even if s ubjects were severely neuropathic. The replication-to-replication and day-t o-day intraclass correlation coefficients for the Maxivibrometer VPT were, except in one case, above 0.94, indicating excellent reliability. The Bioth esiometer VPT could also be measured with excellent reliability but only wi thin a limited range of mild to moderate neuropathy, so it appears to be an appropriate screening tool. The replication-to-replication intraclass corr elation coefficient was 0.93. Conclusions Because VPT could be measured over a wide range with the Maxivi brometer, it was demonstrated that loss of sensation in diabetic neuropathy can progress far beyond the maximum VPT value of the Biothesiometer. The w ide measurement range and the excellent reliability make the Maxivibrometer a valuable research tool to quantify loss of sensation, particularly in th e presence of severe neuropathy and to record changes over time.