Shi, et al. (2023) say that few studies have investigated how the effectiveness of hand washing in removing hand contaminants is influenced by the performance and duration of each step involved. The researchers conducted an observational study by recruiting participants from a university campus, with the aim to comprehensively evaluate how performance, duration and demographic factors influence handwashing effectiveness.

A total of 744 videos were collected from 664 participants in July-October 2022 and independently evaluated by two infection control experts through labelling videos for correct and incorrect performance of each step. The individual handwashing effectiveness was determined by quantifying the percentage of residual fluorescent gel on the dorsum and palm areas of each participant’s hands. A logistic regression analysis was conducted to identify factors that were significantly associated with better handwashing effectiveness. An exposure-response relationship was constructed to identify optimal durations for each step. Approximately 2,300 hand images were processed using advanced normalization algorithms and overlaid to visualize the areas with more fluorescence residuals after hand washing.

Step 3 (rub between fingers) was the most frequently omitted step and step 4 (rub the dorsum of fingers) was the most frequently incorrectly performed step. After adjustment for covariates, sex, performance of step 4 and step 7 (rub wrists), rubbing hands during rinsing, and rinsing time were significantly associated with handwashing effectiveness. The optimal overall hand washing time was 31 s from step 1 to step 7, and 28 seconds from step 1 to step 6, with each step ideally lasting 4–5 seconds, except step 3. The palms of both hands had less fluorescence residuals than the dorsums. The areas where residuals most likely appeared were wrists, followed by fingertips, finger webs and thumbs.

Performance and duration of some handwashing steps, sex and rinsing time were associated with handwashing effectiveness. The researchers say the optimal duration might be applied to all seven steps to achieve the best decontamination results. Further studies are needed to refine hand hygiene standards and enhance compliance.

Reference: Shi C, et al. Factors associated with hand washing effectiveness: an institution-based observational study. Antimicrobial Resistance & Infection Control. Vol. 12, article number 85 (2023).