[PHNUTR-L] Value of the Oral Glucose Tolerance Test in the Evaluation of Chronic Idiopathic Axonal Polyneuropathy

[Kathrynne Holden, MS, RD]

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		Early Release Article, posted June 12, 2006 			

Value of the Oral Glucose Tolerance Test in the Evaluation of Chronic 
Idiopathic Axonal Polyneuropathy

Charlene Hoffman-Snyder, MSN, NP-BC; Benn E. Smith, MD; Mark A. Ross, 
MD; Jose Hernandez, BA; E. Peter Bosch, MD

Arch Neurol. 2006;63:(doi:10.1001/archneur.63.8.noc50336).

Background  An underlying cause is found in only 7% to 30% of patients 
with chronic idiopathic axonal polyneuropathy (CIAP). Diabetes mellitus, 
inherited disorders, toxin exposure, and primary amyloidosis are the 
most common identified causes of sensory neuropathies affecting both 
large and small myelinated fibers. Undiagnosed impaired fasting glucose 
metabolism has been associated with CIAP at a higher frequency rate than 
in the general population. This increased prevalence rate was identified 
using the 2-hour oral glucose tolerance test (2h-OGTT) and a previous 
version of the American Diabetes Association (ADA) guidelines.

Objectives  To determine the prevalence of abnormal fasting glucose 
metabolism in patients with CIAP and to compare the value of determining 
fasting plasma glucose levels using revised (2003) ADA criteria with the 
2h-OGTT for predicting abnormal fasting glucose metabolism.

Patients  In this 24-month retrospective study, 100 consecutive patients 
were identified with no known cause for CIAP, including diabetes 
mellitus, between January 2003 and January 2005. All had both a fasting 
plasma glucose test and a 2h-OGTT in addition to a complete neurological 
examination. Neurophysiological studies, computer-assisted sensory 
examination, and quantitative sudomotor axonal reflex testing were used 
to classify CIAP into subtypes according to nerve fiber involvement.

Results  The prevalence of undiagnosed abnormal fasting glucose 
metabolism was found to be nearly 2-fold higher (62%) in patients with 
CIAP than in similar age-matched general population groups (33%). Using 
the 2003 revised ADA criteria, 39 patients (39%) had abnormal fasting 
plasma glucose metabolism (36 with impaired fasting glucose, 3 with 
diabetes mellitus), while the 2h-OGTT provided an even higher diagnostic 
rate of 62% (62 patients; P<.001) of impaired fasting glucose metabolism 
(38 with impaired glucose tolerance, 24 with diabetes mellitus). The 
abnormal glucose metabolism rates were found to be similar across the 3 
subtypes (sensorimotor, pure sensory, and small-fiber neuropathy) of 
CIAP (P = .60, .72, and .61).

Conclusions  This study adds to emerging evidence that abnormal glucose 
metabolism may be a risk factor for CIAP. Even with revised (2003) ADA 
criteria, the 2h-OGTT provides additional diagnostic information to the 
health care professional in the evaluation of CIAP. Subtypes of CIAP are 
equally likely to have abnormal glucose metabolism.

Published online June 12, 2006 (doi:10.1001/archneur.63.8.noc50336).


Author Affiliations: Departments of Neurology (Ms Hoffman-Snyder and Drs 
Smith, Ross, and Bosch) and Biostatistics (Mr Hernandez), Mayo Clinic 
Scottsdale, Scottsdale, Ariz.
-- 
Kathrynne Holden, MS, RD < fivestar at nutritionucanlivewith.com >
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