A point-of-care conduction device (POCD) may provide accurate measurements of nerve amplitude potential and conduction velocity for the diagnosis of polyneuropathy in older patients, according to a study published in PLoS One.
Unlike nerve conduction studies that require specialized training and equipment, the POCD can be readily used by nonspecialist clinicians for the detection of polyneuropathies.
Use of this technique would be valuable in a subset of patients (eg, those with longstanding type 1 diabetes), who are at high risk for neuropathies but may be in the subclinical phase and thus remain untreated.
In a secondary analysis of the Canadian Study of Longevity in Type 1 Diabetes, investigators measured the conduction velocity and amplitude potential of the sural nerve in patients who had with type 1 diabetes for ≥50 years (n=68; 53% women; mean age, 66 years; mean type 1 diabetes duration, 54 years) and sex- and age-matched individuals who did not have diabetes (n=71; 56% women; mean age, 65 years), using both the POCD and standard nerve conduction studies.
The mean sural nerve amplitudes were 7.4±5.8 µV and 7.2±6.1 µV (mean difference, 0.3±3.8 µV), and the mean sural nerve conduction velocities were 45.7±11.2 m/sec and 43.3±8.3 m/sec (mean difference, 2.3±8.5 m/sec), as measured with the POCD and nerve conduction study, respectively. Patients with type 1 diabetes vs controls were found to have lower sural nerve potential amplitudes and conduction velocities when measured both with POCD and nerve conduction studies (P <.001 for all).
With the POCD, a sural nerve potential amplitude ≤6 µV had 80% sensitivity and 80% specificity for detecting abnormal potential amplitudes as measured with nerve conduction studies, and a conduction velocity ≤44 m/sec had 81% sensitivity and 82% specificity for identifying abnormal conduction velocities, as indicated by nerve conduction studies.
Abnormalities in either potential amplitude or conduction velocity (as measured with the POCD) had 86% sensitivity and 79% specificity, and abnormalities in both measures had 66% sensitivity and 97% specificity. Using a clinical algorithm allowing for more stringent specificity and sensitivity with the POCD, the researchers assessed that the device could determine the presence of polyneuropathy in 82% of patients, with the remaining 18% requiring further tests.
Study limitations include a possible selection bias resulting from the inclusion criteria of only people who had diabetes for ≥50 years, a high prevalence of polyneuropathy in the study cohort that may not be representative of patients in general practice, and assessment of the POCD on the sural nerve only.
“[T]he diagnostic performance and POCD-specific thresholds in older adults with longstanding [type 1 diabetes] — despite any age-related changes in nerve conduction — were similar to those reported in younger adults with diabetes, implying that this device can be used as a valid screening test for polyneuropathy across broadly-aged adult populations,” concluded the investigators.
Conflicts of Interest
The study’s senior author serves as a consultant for NeuroMetrix which manufactures the POCD.
Scarr D, Lovblom LE, Cardinez N, et al. Validity of a point-of-care nerve conduction device for polyneuropathy identification in older adults with diabetes: results from the Canadian Study of Longevity in Type 1 Diabetes. PLoS One. 2018;13(4):e0196647.