Int Arch Occup Environ Health ( 1989) 61:431-435 Intemational Archives of O Cpai Oand- Environmental Springer-Verlag 1989th Springer-Verlag 1989 Quantitative estimation of aesthesiometric thresholds for assessing impaired tactile sensation in workers exposed to vibration Massimo Bovenzil and Antonella Zadini 2 'Institute of Occupational Health, University of Trieste, Centro Tumori, 1-34129 Trieste, Italy 2 Rehabilitation Center, National Health Service, Ospedale Maggiore, 1-34129 Trieste, Italy Summary To evaluate the usefulness of aesthesio- metric threshold testing in the quantitative assessment of peripheral sensorineural disorders occurring in the hand-arm vibration syndrome, two point discrimina- tion (TPD) and depth sense perception (DSP) thresh- olds 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 as- sumptions, 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 ob- tained 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 dif- ferentiate 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 vibra- tion exposed patients, it was unsuitable to confirm ob- jectively 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. Key words: Aesthesiometry Healthy subjects Tac- tile function Vibration exposure Offprint requests to: M Bovenzi Introduction Sensorineural disturbances, such as tingling and numb- ness in the fingers and hands, have been frequently reported by workers exposed to hand-arm vibration l 2, 3, 11 l Symptoms and signs of sensory impairment as early manifestations of peripheral neuropathy may also occur in manual workers affected with nerve trunk entrapments (e g carpal tunnel syndrome) or in operators exposed to neurotoxic organic substances (e.g n-exane) l 1 l At present, only a few objective tests are available to assess quantitatively sensori- neural function in worker groups exposed to physical or chemical agents involving the peripheral nervous systems In some studies of the hand-arm vibration (HAV) syndrome, aesthesiometry (two point dis- crimination and depth sense perception) has been used to examine fingertip sensation in workers operat- ing vibrating tools l 5-9 l The results of these studies suggest that tactile dicrimination and sensory percep- tion are reduced in the advanced stages of vibration in- duced neuropathy These findings have been ascribed to the adverse effect of segmental vibration on the in- tegrity or functional capacity of skin mechanorecep- tors of slowly adapting (SA I) and, probably, fast adapting (FA I) types l 2 l In order to evaluate the severity of the sensorineural component of the HAV syndrome, it is essential to quantify tactile sensation in vibration exposed patients by measuring aesthesio- metric thresholds and comparing the observed thresh- old values with those from controls Owing to differ- ences in instrument design and testing procedures used by various researchers, the upper normal limits of aesthesiometric thresholds for healthy individuals vary widely Hence, comparable data on tactile func- tion of normal populations are needed For this pur- pose, the present paper reports the results of depth sense and two point discrimination measurements performed on a large sample of healthy male subjects