Reliability of a visual scoring system with fluorescent tracers to assess dermal pesticide exposure

We modified Fenske's semi-quantitative 'visual scoring system' of fluorescent tracer deposited on the skin of pesticide applicators and evaluated its reproducibility in the Nicaraguan setting.

The body surface of 33 farmers, divided into 31 segments, was videotaped in the field after spraying with a pesticide solution containing a fluorescent tracer. A portable UV lamp was used for illumination in a foldaway dark room. The videos of five farmers were randomly selected. The scoring was based on a matrix with extension of fluorescent patterns (scale 0-5) on the ordinate and intensity (scale 0-5) on the abscissa, with the product of these two ranks as the final score for each body segment (0-25). Five medical students rated and evaluated the quality of 155 video images having undergone 4 h of training. Cronbach alpha coefficients and two-way random effects intraclass correlation coefficients (ICC) with absolute agreement were computed to assess inter-rater reliability.

Consistency was high (Cronbach alpha = 0.96), but the scores differed substantially between raters. The overall ICC was satisfactory [0.75; 95% confidence interval (CI) = 0.62-0.83], but it was lower for intensity (0.54; 95% CI = 0.40-0.66) and higher for extension (0.80; 95% CI = 0.71-0.86). ICCs were lowest for images with low scores and evaluated as low quality, and highest for images with high scores and high quality.

Inter-rater reliability coefficients indicate repeatability of the scoring system. However, field conditions for recording fluorescence should be improved to achieve higher quality images, and training should emphasize a better mechanism for the reading of body areas with low contamination.