Quantitative estimation of aesthesiometric thresholds for assessing impaired tactile sensation in workers exposed to vibration

To evaluate the usefulness of aesthesiometric threshold testing in the quantitative assessment of peripheral sensorineural disorders occurring in the hand-arm vibration syndrome, two point discrimination (TPD) and depth sense perception (DSP) thresholds were measured by means of two aesthesiometers in the fingertips of 65 forestry workers exposed to chain saw vibration and 91 healthy males unexposed to local vibration or neurotoxic chemicals. Among the healthy subjects, divided into three age groups, there was no difference in the mean values of TPD and DSP thresholds. Assuming 1.28 or 2 standard deviations above the mean to be the upper limits of normality, in the present study the threshold values for TPD were 2.5 and 3.13 mm, respectively. Using the same assumptions, the normal threshold values for DSP were 0.36 and 0.49 mm. Among the 65 chain saw operators the prevalence of peripheral sensory disturbances was 70.8%. On the basis of the aesthesiometric results obtained for the group of 46 chain sawyers affected with sensorineural symptoms and a control group of 46 manual workers, the specificity of the aesthesiometric testing method was found to range between 93.4 and 100%, while the sensitivity varied from 52.2 to 71.7%. In its predictive value aesthesiometry had a positive accuracy of 84.6–96.0% and a negative accuracy of 42.8–50.0%. Aesthesiometric testing was able to differentiate between normals and vibration workers with sensory disturbances on a group basis (P < 0.001), but due to the high rate of false negatives among vibration exposed patients, it was unsuitable to confirm objectively sensorineural symptoms on an individual basis. We conclude that aesthesiometry may be used in field surveys for epidemiological purposes to assess peripheral sensory disorders in exposed groups at risk.