Reliability and validity of a point-of-care sural nerve conduction device for identification of diabetic neuropathy.
BACKGROUND
Confirmation of diabetic sensorimotor polyneuropathy (DSP) relies on standard nerve conduction studies (NCS) performed in specialized clinics. We explored the utility of a point-of-care device (POCD) for DSP detection by nontechnical personnel and a validation of diagnostic thresholds with those observed in a normative database.


METHODS
44 subjects with type 1 and type 2 diabetes underwent standard NCS (reference method). Two nontechnical examiners measured sural nerve amplitude potential (SNAP) and conduction velocity (SNCV) using the POCD. Reliability was determined by intraclass correlation coefficients (ICC [2], [1]). Validity was determined by Bland-Altman analysis and receiver operating characteristic curves.


RESULTS
The 44 subjects (50% female) with mean age 56 ± 18 years had mean SNAP and SNCV of 8.0 ± 8.6 µV and 41.5 ± 8.2 m/s using standard NCS and 8.0 ± 8.2 µV and 49.9 ± 11.1 m/s using the POCD. Intrarater reproducibility ICC values were 0.97 for SNAP and 0.94 for SNCV while interrater reproducibility values were 0.83 and 0.79, respectively. Mean bias of the POCD was -0.1 ± 3.6 µV for SNAP and +8.4 ± 6.4 m/s for SNCV. A SNAP of ≤6 µV had 88% sensitivity and 94% specificity for identifying age-and height-standardized reference NCS values, while a SNCV of ≤48 m/s had 94% sensitivity and 82% specificity [corrected].. Abnormality in one or more of these thresholds was associated with 95% sensitivity and 71% specificity for identification of DSP according to electrophysiological criteria.


CONCLUSIONS
The POCD demonstrated excellent reliability and acceptable accuracy. Threshold values for DSP identification validated those of published POCD normative values. We emphasize the presence of measurement bias--particularly for SNCV--that requires adjustment of threshold values to reflect those of standard NCS.
Division of Endocrinology and Metabolism, Department of Medicine, University of Toronto, Ontario, Canada.
Justin A
JA
Lee
Division of Endocrinology and Metabolism, Department of Medicine, University of Toronto, Ontario, Canada.
Elise M
EM
Halpern
Division of Endocrinology and Metabolism, Department of Medicine, University of Toronto, Ontario, Canada.
Leif E
LE
Lovblom
Division of Neurology, Department of Medicine, University of Toronto, Ontario, Canada.
Emily
E
Yeung
Division of Neurology, Department of Medicine, University of Toronto, Ontario, Canada.
Vera
V
Bril
Division of Endocrinology and Metabolism, Department of Medicine, University of Toronto, Ontario, Canada.
Bruce A
BA
Perkins
D000328:Adult; D000368:Aged; D003929:Diabetic Neuropathies / Q000175:diagnosis* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009431:Neural Conduction; D019095:Point-of-Care Systems; D012372:ROC Curve; D015203:Reproducibility of Results; D013497:Sural Nerve / Q000503:physiopathology*