Utility of vibration sense testing for use in developing countries: comparison of extinction time on the tuning fork...

The measurement of vibration sense loss is a useful tool to detect early impacts of neurotoxic chemicals. Measurement methods are needed for developing countries that are culturally unbiased, and which can be used under field conditions where electricity may be unavailable. Extinction time on a 256 Hz tuning fork was compared to vibration threshold measured on the Vibratron II for precision and agreement amongst 306 fruit farm workers as part of a study investigating neurobehavioural impacts of organophosphates in South Africa in 1993. Simultaneous data were also available from a 1 g accelerometer attached to the post of the Vibratron for comparisons. Precision of the tuning fork and Vibratron II appeared comparable and CVs (2.5 to 8.9%) were lower than that reported in the literature. Agreement of the tuning fork with the Vibratron was moderate (Spearmans correlation coefficient of the order of 0.39 to 0.42) whereas agreement between Vibratron and Accelerometer was high (Spearmans correlation of coefficient of the order of 0.78 to 0.83). Height, age and schooling were predictors of vibration sense for the Vibratron and accelerometer but only schooling for extinction time on the tuning fork. Height modified the variability of the Vibratron and accelerometer. Delays in application of the tuning fork to the base of the medial malleolus of 3 seconds or more were associated with average increases in extinction time of 1.7 s. The tuning fork, as standardised in this study, represents a relatively quick, easy and low-technology device with good utility, that is relatively resistant to the usual confounders for vibration threshold measurement. Further studies to explore its validity in relation to other well-recognised methods for detection of subtle neurotoxic impacts should be encouraged.