Results of a tuning fork test to identify neuropathy appear to be reproducible in a nondiabetic population, according to findings from a blinded, observational study. Dr. David S. Oyer of Northwestern University, Chicago, Ill., described how he used a tuning fork test to evaluate 147 patients aged 40 years and older.
To perform the test, a C128 tuning fork was struck to make the ends clang together, and then patients were shown the difference between the vibration sensation and pressure on the patient’s toe, malleolus, knee, or sternum. The tuning fork test was performed again at the end of the dorsal bony prominence of the patient’s big toe proximal to the nail. Blinded, the patients then indicated when they could no longer feel the vibration.
Vibration sensation duration was measured in both feet twice. Average scores were then analyzed for correlations between the right versus left foot, statin versus nonstatin use, and overall difference in sensation by age-group decade. Overall, 80% of patients were within 2 seconds between the right and left feet, suggesting the test’s consistency.
The average score for all patients was 12.8 ± 4.7 seconds. Average scores were 14.3 seconds for patients aged 40–49, 14.1 seconds for patients aged 50–59, 12.2 seconds for patients aged 60–69, 9.4 seconds for patients aged 70–79, and 4.8 seconds for patients aged 80–89. There was an average 1.43-second longer vibration sensation in patients not on statins, the researchers noted.
The investigators determined that normal score cutoff values were above 7.5 seconds in those aged 40–49, 6.9 seconds in the 50–59 age group, and 3.8 seconds in the 60–69 age group.
Patients’ sex, alcohol use, height, NSAID use, smoking history, and other unknown factors may explain the variability in the test results, the researchers suggested. Larger studies may help reduce the degree of variability by age group.
The findings dovetail with those from a previous investigation in which Dr. Oyer found that the tuning fork test was far more effective than the more widely used monofilament test in detecting distal polyneuropathy. That study involved 45 diabetes patients who had vibration test scores of 0–8 seconds, indicating some level of neuropathy. Of those 45 patients, only 16 had abnormal monofilament test results (Endocr. Pract. 2004;10[Suppl. 1]:20).
“The clanging tuning fork test detects neuropathy at a much earlier stage than the monofilament test,” Dr. Oyer said in an interview. “It can be an accurate gauge of somebody’s neuropathy” and encourage them to better blood sugar control to prevent future problems.
Presented at the annual meeting of the American Association of Clinical Endocrinologists