A 4, 2, AND 1 STEPPING ALGORITHM FOR QUICK AND ACCURATE ESTIMATION OF CUTANEOUS SENSATION THRESHOLD

In quantitative sensory testing, certain methods may lead to incorrect estimates of vibratory (VDT), cool (CDT), or warm (WDT) detection thresholds. We have shown that the specific forced-choice algorithm of testing employed in our Computer-Assisted Sensory Examination (CASE IV) system, when compared with other tests of nerve dysfunction, provides accurate and reproducible estimates of these thresholds. Because this forced-choice algorithm is time consuming and performance might be made worse by drowsiness or boredom, we explored other algorithms that might provide estimates of threshold similar to those obtained with the forced-choice algorithm, but more quickly. In a trial of 25 healthy subjects and 25 patients with neuropathy, the 4, 2, and 1 stepping algorithm with null stimuli, based in part on comparative data from computer simulation and insights from patient decision making, provides an accurate estimate of threshold. On average, the time needed for forced-choice testing was 12.8 +/- 2.9 minutes (mean +/- SD). For 4, 2, and 1 stepping testing, it was 2.7 +/- 2.5 minutes-a large saving of time. Since null stimuli were employed in the 4, 2, and 1 stepping algorithm, it was possible to monitor for spurious responses and repeat the test if they occurred at an excessive rate. The algorithm appears to be sufficiently robust to be recommended for clinical use and for some controlled clinical and epidemiologic trials.