Selection of patients with symptomatic diabetic neuropathy for clinical trials

Two hundred and fourteen patients with prima-facie evidence of symptomatic diabetic neuropathy were considered for inclusion in a clinical trial. Only 50 patients (24%) fulfilled all the clinical and electrophysiological criteria for entry. One hundred and nine patients (51%) were excluded on clinical grounds alone. Reasons for exclusion included the presence of alternative causes of neuropathy (15%), peripheral vascular disease (10%), proximal or asymmetrical neuropathies (11%), renal impairment (5%), nerve entrapment (4%), cerebrovascular disease (2%) and amputations (2%) with miscellaneous conditions accounting for the remaining 2%. Of the 105 patients who satisfied the clinical entry requirements another 55 patients (26%) were excluded by electrophysiological criteria. Peroneal motor nerve conduction velocity was unrecordable or unacceptably reduced (less than 30 m/s) in 42% of these patients, sensory nerve potentials were unrecordable in 8% and median nerve compression was evident in another 3%. The selection of cohorts for clinical trials in diabetic neuropathy involves careful consideration of clinical and electrophysiological features of the patients and exclusion of alternative causes of neuropathy.