Table 2. Comparison of Area Under the Receiver Operating Characteristic Curve (AROC) Between Individual and Summative NCS Parameters for the Cross-Cectional (Concurrent Validity) Analysis and the Longitudinal (Predictive Validity) Analysis.
| Operating characteristics of the optimal threshold values | ||||||
| Test | Area under the ROCcurve | P Value* | Standard Threshold Values for Normality† | Optimal Threshold Values | Sensitivity | Specificity |
| Concurrent Validity | ||||||
| Peroneal CV (m/s) | 0.90 | – | >40 | 40.4 | 0.80 | 0.89 |
| Individual NCS Parameter | ||||||
| Sural Amp (µV) | 0.83 | 0.36 | Age ≤65: >7.2 | 4.9 | 0.83 | 0.72 |
| Age >65: >5.5 | ||||||
| Sural CV (m/s) | 0.80 | <0.0001 | >40 | 42.1 | 0.68 | 0.79 |
| Peroneal Amp (mv) | 0.81 | 0.002 | Age ≤65: >5 | 4.7 | 0.84 | 0.75 |
| Age >65:>3 | ||||||
| Peroneal F-wave (ms) | 0.85 | 0.0005 | Ht≥182.9: <59 | 53.6 | 0.85 | 0.71 |
| Ht <182.9: <58 | ||||||
| Tibial Amp (mV) | 0.76 | <0.0001 | >10 | 5.7 | 0.68 | 0.75 |
| Tibial CV (m/s) | 0.82 | <0.0001 | >40 | 40.5 | 0.79 | 0.76 |
| Tibial F-wave (ms) | 0.81 | <0.0001 | <58.5 | 58.5 | 0.78 | 0.69 |
| Summative NCS Parameter | ||||||
| Amp (arbitrary units) | 0.86 | 0.87 | Age ≤65: >17.2 | 16.5 | 0.83 | 0.76 |
| Age <65: >15.5 | ||||||
| CV (m/s) | 0.89 | 0.47 | >120 | 123.3 | 0.80 | 0.84 |
| F-wave (ms) | 0.86 | 0.04 | Ht≥182.9: <114 | 112.1 | 0.84 | 0.74 |
| Ht <182.9: <113 | ||||||
| Predictive Validity | ||||||
| Tibial F Wave (ms) | 0.79 | – | <58.5 | 57.6 | 0.79 | 0.63 |
| Individual NCS Parameter | ||||||
| Sural Amp (µV) | 0.71 | 0.08 | Age ≤65: >7.2 | 6.8 | 0.71 | 0.68 |
| Age >65: >5.5 | ||||||
| Sural CV (m/s) | 0.76 | 0.32 | >40 | 44.1 | 0.75 | 0.65 |
| Peroneal Amp (mV) | 0.65 | 0.0006 | Age ≤65: >5 | 6.2 | 0.57 | 0.68 |
| Age >65: >3 | ||||||
| Peroneal CV (m/s) | 0.79 | 0.89 | >40 | 42.4 | 0.74 | 0.70 |
| Peroneal F Wave (ms) | 0.75 | 0.87 | Ht≥182.9: <59 | 51.8 | 0.67 | 0.78 |
| Ht <182.9: <58 | ||||||
| Tibial Amp (mV) | 0.63 | 0.0005 | >10 | 8.4 | 0.57 | 0.60 |
| Tibial CV (m/s) | 0.77 | 0.06 | >40 | 41.4 | 0.80 | 0.64 |
| Summative NCS Parameter‡ | ||||||
| Sum Amp (arbitrary units) | 0.71 | 0.03 | Age ≤65: >17.2 | 22.8 | 0.59 | 0.76 |
| Age <65: >15.5 | ||||||
| Sum CV (m/s) | 0.85 | 0.15 | >120 | 129.1 | 0.81 | 0.77 |
| Sum F Wave (ms) | 0.79 | 0.09 | Ht≥182.9: <114 | 110.1 | 0.80 | 0.65 |
| Ht <182.9: <113 | ||||||
Normal values for individual NCS are as follows. Sural amp≥7.2 µV for age ≤65 and ≥5.5 µV for age >65, sural CV≥40 m/s, peroneal amp≥5 µV for age ≤65 and ≥3 for age >65, peroneal CV≥40 m/s, peroneal F wave ≤59 ms for height ≥182.9 cm and ≤58 ms for height ≤182.9 cm, tibial amp≥10 µV, tibial CV≥40 m/s, tibial F wave ≤55 ms.
Two tailed p value for comparison with the AROC for the parameters with the highest AROC in concurrent and predictive analyses.
Established by the distribution in healthy control subects [23].
Summative parameters are composed of the following: sum amplitude = sural+tibial, sum conduction velocity = sural+peroneal +tibial, sum F-wave latency = peroneal+tibial. Summed amplitude potentials are expressed in arbitrary units since sural amplitude potential is measured in microvolts and tibial amplitude potential is measured in millivolts.
Amp, amplitude potential. CV, conduction velocity. F-wave, F-wave latency.