A simplified diagnostic test for ambulatory screening of peripheral diabetic neuropathy

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Abstract

The reliability and reproducibility of Michigan Neuropathy Screening Instrument (MNSI), a recently proposed simple test for ambulatory screening of peripheral diabetic neuropathy (PDN), was evaluated on 80 diabetic patients. MNSI was carried out by two diabetologists and repeated after a week. It consisted of the sum of scores varying from 0 to 1 for each abnormality revealed in foot appearance, achilles reflexes presence and vibratory threshold (VPT) by tuning fork (maximum score=8). Then patients had to go to neurologist for PDN diagnosis by a quantitative neurological examination and electrophysiological evaluation, the so named Michigan Diabetic Neuropathy Score (MDNS) and the results compared with MNSI score according to one of the two observers. The inter-observer reproducibility of MNSI was 88.75% the within observer reproducibility was 95 and 94%, respectively, for each observer with good correlation between the two measurements (P<0.001). The MNSI score of 2.5 as a cut-off appeared to be reliable for ambulatory screening of suspected PDN (false positive and false negative=2.5%; specificity and sensitivity=75% and 78.6%, respectively). In conclusion MNSI by using 2.5 score as cut-off may be considered a rapid, simple, reproducible and reliable test for rapid ambulatory screening of PDN from the diabetologists.

Introduction

The ambulatory screening of the diabetic neuropathy (DN), a frequent diabetic complication [1], presented a lot of methodology difficulties. The San Antonio Consensus Conference [2]proposed some criteria for diagnosis (evaluation of symptoms, objective neurological examination, quantitative tests for sensitivity, autonomic nervous function tests and nervous conduction studies), alterations of at least two of these parameters need for diagnosis of DN [3]. These tests aren’t easy to be applied in the ambulatory screening of DN, the procedure being rather complex, though they are valid to formulate the diagnosis of DN with the greatest reliability 3, 4. For this reason a new screening methodology has been proposed, the Michigan Neuropathy Screening Instrument (MNSI) based on a simple test administered by the diabetologist [5]. The patients, who resulted positive on the MNSI, may be referred for administration by neurologist of the Michigan Diabetic Neuropathy Score (MDNS) which consists of a quantitative neurological examination and a set of nerve conduction studies [5]. In accordance with this project, the diabetologist should make the screening of the subjects suspected of neuropathy and the neurologist should complete the diagnosis (Neuropathy Circles Project) 5, 6.

The aim of this study was the evaluation of MNSI reproducibility and its validation as an instrument of rapid screening towards the diagnosis of peripheral neuropathy using MDNS as a reference method.

Section snippets

Study population

A total of 80 diabetic outpatients, of both sexes, of which 25 were affected by type 1 diabetes and 55 by type 2 diabetes as classified according to the National Diabetes Data group criteria [7], with disease duration of more than 10 years, aged under 60 years and treated with insulin and oral hypoglycaemic agents, respectively, were enrolled in the study. None of them had previously carried out tests for diabetic neuropathy. Alcoholic neuropathy could be excluded since patients usually did not

MNSI by diabetologists

The total points scored wasn’t different for the two observers (3.8±0.4 and 3.7±0.3, respectively) and the reproducibility between observer (error more than 0.5 score) was 88.75%. Within observer reproducibility was 95 and 94%, respectively, for each observer, the score in the two measurements was 3.8±0.4 versus 3.6±0.5 and 3.7±0.3 versus 3.9±0.4, P=ns, the correlation index r=0.71 and r=0.76, respectively (P<0.001). Since in clinical practice only one observer will screen the patients and the

Discussion

This study has been carried out by considering only patients with high risk of neuropathy, their diabetes having a duration of 10 years or more. The findings confirm that MNSI using a 2.5 score as cut-off, is a very rapid screening method for suspected PDN (about 4–5 min.), with a good reproducibility between observer and within observer and an acceptable sensitivity and specificity for PDN diagnosis. The good correlation between MNSI and MDNS clinical score demonstrates the effectiveness of

Conclusion

MNSI can be considered as a simple and rapid method for the ambulatory screening of suspected PDN by diabetologist with specific training with great time and money saving. A complete neurological visit and a complete electroneurological study of upper and lower limb nerves, as well as autonomic nervous system testing, could be carried out only in MNSI positive subjects in order to confirm diagnosis and to establish the type and stadiation of diabetic neuropathy.

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