Diagnostic accuracy of qualitative versus quantitative tuning forks: outcome measure for neuropathy

To assess the diagnostic accuracy of the Rydel-Seiffer tuning fork versus the qualitative 128-Hz tuning fork for detecting sensory axonal neuropathy.

One hundred consecutive patients seen at the Neurology Outpatient Electromyography clinic at a major academic center were recruited and consented for this study. Study personnel who were blinded to results of nerve conduction studies collected data on vibratory perception with both tuning forks at bilateral (1) great toe and (2) distal interphalangeal joint on the second digit. Published normative data were used to determine abnormal scores for the Rydel-Seiffer tuning fork and the qualitative tuning fork; axonal neuropathy was determined based on sensory nerve action potential amplitudes as per our electromyography laboratory standards.

A total of 186 sensory nerves from 100 patients were tested with tuning forks and nerve conduction studies. The sensitivity and specificity of the Rydel-Seiffer tuning fork to detect axonal neuropathy was 26% and 89%, respectively, and the sensitivity and specificity of the conventional 128-Hz tuning fork to detect axonal neuropathy was 20% and 88%, respectively. The extended McNemar test showed no significant difference in sensitivity or specificity between the 2 tuning forks (χ = 1.695; P = 0.43).

There is no difference in diagnostic accuracy between the Rydel-Seiffer tuning fork and conventional tuning fork for detecting sensory axonal neuropathies; however, the Rydel-Seiffer is easier to use and may be superior for longitudinal assessments.