REPRODUCIBILITY OF PARAMETERS FOR ASSESSMENT OF DIABETIC NEUROPATHY

This study evaluated the reproducibility of nerve function assessment in a group of 132 diabetic patients with moderate peripheral polyneuro pathy. Patients were investigated at the beginning and the end of the run-in period (a 1-month placebo period) of a multicentre trial of an aldose-reductase inhibitor (Ponalrestat). Reproducibility was evaluate d by performing four types of tests: quantitative visual scales of sym ptoms, quantitative sensory assessment (vibration perception threshold s in medial malleolus and great toe, foot thermal perception threshold to hot and cold), electrophysiological investigations on the dominant side (conduction velocities and potential amplitudes of sensory and m edian motor nerve, sural and peroneal nerves, amplitudes of F waves of median motor and peroneal nerves) and cardiac autonomic tests (Valsal va, deep-breathing, lying-to-standing), Reproducibility was poor for s ymptoms, thermal sensitivity, and potential amplitudes. It was satisfa ctory (total coefficient of variation < 50 %) for all the other parame ters and even very good (total variation coefficient < 26 %, intra-sub ject variation factors corresponding to < 56 % of total variance) for velocities of sensory and median motor and peroneal nerves, the amplit udes of F waves and the three autonomic tests. For most of the paramet ers total variance was mainly related to inter-subject variability. Ho wever, inter-subject variability for the three cardiac autonomic tests was very low and at least one cardiac autonomic test was altered in a ll the patients. Inter-centre variability was low for all the paramete rs, except for action potential amplitudes and for F wave velocity of the median motor nerve. This study suggests those parameters that are appropriate for the assessment of diabetic neuropathy and for therapeu tic trials. It also shows evidence of cardiac autonomic neuropathy in all these patients with moderate peripheral neuropathy.