Abnormality Rate Comparison of Median and Sural NCS for Patients Tested for DPN
Abstract Number: 2214-PO
Authors: XUAN KONG, SHAI N. GOZANI, JONATHAN T. MEGERIAN.
Institutions: Waltham, MA; Boston, MA.
Results: Introduction. Neuropathies are one of the most prevalent chronic complications of diabetes. A recent study based on an analysis of 39 patients and 40 healthy controls reported that median sensory nerve action potential (SNAP) amplitude had a 70% abnormality rate while the sural SNAP amplitude was abnormal in only 22% of newly diagnosed type II diabetic patients The NC-stat® is a widely used point-of-service NCS system which electronically logs data to a central registry. This centralized NCS database facilitates large scale quantitative studies of neuropathies and was used to analyze SNAP abnormality rates in diabetics with a higher statistical power.
Methods. NCS completed between October 2003 and July 2004 were considered. Studies performed exclusively for assessment of DPN and for which sural sensory and median motor/sensory electrophysiology from either limb was available were analyzed. Sensory amplitude abnormality was defined at the 2.5th percentile. Median neuropathy at the wrist (CTS) was defined as normal F-wave latency (< 97.5th percentile) with prolonged distal motor latency (> 97.5th percentile).
Results. A total of 4,456 studies met the inclusion criteria. 69.9% of the patients were >60 years and 52% were female. 74.6% of the studies had a sural abnormality, and 62.9% had a median sensory abnormality. Excluding CTS cases, the median sensory abnormality rate dropped to 52.7%. The sural and median sensory abnormality rates were 80.0% and 66.0% for males, respectively; and 69.5%, and 40.4% for female subjects, respectively. For patients younger than 60, the abnormality rates were 68.4%, 58.8%, and 50.7%. For older patients, the rates were 77.2%, 64.6%, and 53.5%. For subjects with normal DML (n=2234), the sural and median SNAP abnormality rates are 67.5% and 43.3%.
Conclusions. This preliminary analysis suggests that DPN is common among diabetic patients. The sural SNAP abnormality rate is higher than for the median SNAP, and thus is likely to be a more sensitive NCS indicator of DPN.