QUEBEC CITY — Noninvasive methods for identifying pediatric diabetic neuropathy are not as sensitive as conventional nerve conduction studies and should not be considered for screening purposes, Danièle Pacaud, M.D., said at the joint annual meeting of the Canadian Diabetes Association and the Canadian Society of Endocrinology and Metabolism.
“[Noninvasive methods are] fast, less painful, and they don't require a neurology referral, but unfortunately they are also not as good,” she reported regarding new research.
Long-standing diabetic neuropathy can be associated with serious complications such as foot ulcerations, amputations, nephropathy, myocardial infarction, and stroke, said lead investigator Dr. Pacaud, a pediatric endocrinologist at the Alberta Children's Hospital and the University of Calgary in Calgary, Alberta.
Early detection could reduce or delay such complications, but this condition can often exist subclinically, she said.
In adults, two inexpensive, rapid screening tests—the vibration perception thresholds (VPT), and the tactile perception thresholds (TPT)—have been recommended for detecting subclinical neuropathies. However, these tests have not been well assessed in children, she said.
The study compared VPT and TPT with the standard nerve conduction studies (NCS) in 73 children (mean age 13 years) with type 1 diabetes.
The NCS measures median and peroneal motor nerve conduction, as well as sural sensory nerve response. Two abnormalities on this test indicate diabetic neuropathy.
In VPT testing, subjects are asked to touch a box with their big toe and indicate whether it is vibrating. The amplitude of the vibrations is steadily decreased until the subjects cannot feel them.
In TPT, subjects are asked to indicate when they feel microfilaments that are applied to the plantar surface of the foot.
All children in the study were administered a neurological questionnaire by a research coordinator. They also underwent NCS and received a neurological exam by a neurologist. In addition, the children were given both the VPT and TPT by a research nurse. Finally, a research assistant performed a chart review to obtain information on hemoglobin A1c levels and duration of diabetes. All four investigators were blinded to the results obtained by the others.
The study found that, according to the standard NCS, diabetic neuropathy was common. Of the 73 subjects, 42 (57%) had two abnormalities on NCS, indicating diabetic neuropathy.
Of those abnormalities, 37 were picked up by VPT, 26 by neurological exam, and 19 by TPT.
“Compared to the gold standard NCS, neither the VPT, TPT, nor neurological exam was found to be acceptable as [a screening test],” Dr. Pacaud said.
Consistent with other reports, significant variables found to be related to the presence of neuropathy included age, height, degree of metabolic control, and an abnormal neurological exam.
Dr. Pacaud said the neurological symptoms questionnaire was not useful, because few patients experienced regular symptoms.
Although at present, early detection of subclinical diabetic neuropathy would not change a patient's treatment, there may soon be treatments available for this indication, Dr. Pacaud noted.
“At this point, the only treatment we would offer would be to reinforce the importance of metabolic control, which we are already trying to do. However, there are some specific therapies that are being tested, and once they become available it would be important to be able to use screening to identify which individuals would be able to benefit,” she told this newspaper, including aldose reductase inhibitors, certain nutritional supplements, and antioxidant therapies.