Sensory perception testing by monofilaments in the digits of controls and workers with HAVS

To determine if heavy manual work affects sensory perception in the digits and whether Semmes-Weinstein monofilaments (SWM) can be used as a screening tool to detect sensory neuropathy in the digits of workers exposed to hand-transmitted vibration (HTV).

A cross-sectional study of office workers, heavy manual workers not exposed to HTV and workers with hand-arm vibration syndrome (HAVS). Sensory perception was measured in the digits by SWM using a forced-choice method to determine variability by sex, age, hand and digit. Frequency distributions were used to determine limit values and linear weighted kappa for intra-digit variability. Poisson regression was used to explore the relationship between sensory perception by SWM and abnormalities of thermal and vibration perception in the hands of workers with HAVS.

The sensory perception threshold of office workers did not vary by hand or digit. It was significantly lower in women < 30 than women aged ≥ 30 years. The 95th percentile for heavy manual workers was 1.00 (95% CI 0.60-1.00) and significantly higher than for office workers at 0.16 (95% CI 0.16-0.16). Heavy manual workers > 50 years had the highest threshold at 1.40 (95% CI 1.00-2.00). Weighted kappa for reliability was 0.63 (95% CI 0.53-0.70). A mean SWM threshold of ≥ 1.0 gram-force had a 79% sensitivity and 64% specificity for detecting abnormalities of thermal and vibration perception in the ipsilateral index and little fingers of workers with HAVS.

SWM are a useful screening tool for detecting sensory loss in the digits of workers exposed to HTV.