USE OF IMAGE-ANALYSIS TO MEASURE HANDWASHING EFFECTIVENESS

Background: This study tested a unique quantification technology (image analysis of fluorescent particles) for the measurement of handwashing effectiveness, comparing an automated system with traditional manual handwashing. In this instance, handwashing ''effectiveness'' was defined as ability of the technique to remove surface soil, as opposed to removal of microorganisms. Methods: Sixty-five subjects washed their hands by manual handwashing (day 1) and automated handwashing (day 2). Hands were coated with an oil-based fluorescent suspension, photographed under controlled conditions, washed for 10 seconds, and rephotographed. Photographs from before and after handwashing were subjected to image analysis. Results: Manual handwashing removed 73.1% of the particles; the automated method removed 23.2%. Parameters for use of image analysis as a technique to examine removal of gross contamination from the hands are given in the text. Conclusions: Although this method will not replace traditional culture methods for examining microbial removal, it is useful for measuring removal of particles (gross contamination) from skin or other surfaces. Under the conditions tested, manual handwashing was found to be decidedly superior to use of an automated system for removal of oil-based soil on the hands.