Evaluation of 15-second alcohol-based hand rub efficacy: A multi-laboratory study using a modified EN 1500 protocol

Hands are a key vector for pathogen transmission in healthcare, making effective hand antisepsis crucial for infection prevention. According to the European standard EN 1500, the reference method for evaluating hand antiseptics, a minimum rub-in time of 30 seconds using is required. However, observations show healthcare workers typically spend less time on hand antisepsis. To assess the feasibility of a reduced rub-in time under standardized conditions, the German Association for Applied Hygiene conducted a multicenter ring trial in 14 laboratories using a modified EN 1500 protocol (15 seconds, 3 mL of 60% v/v propan-2-ol). In a randomized crossover design, volunteers’ hands were contaminated with E. coli K12 and treated either with the reference (2 × 3 mL / 2 × 30 seconds) or the test protocol (1 x 3 mL / 15 seconds). Microbial reduction was measured and non-inferiority statistically analyzed. The 15-second protocol yielded significantly lower log 10 reductions compared to the reference in 13 out of 14 laboratories but demonstrated consistent reproducibility and satisfactory interlaboratory performance. Challenges in completing the full rub-in technique within 15 seconds were reported, indicating the need for targeted training. These findings support the methodological feasibility of a shortened protocol and are consistent with evolving clinical guidelines advocating reduced rub-in times, as well as with real-world practice, where healthcare workers typically spend less than 30 seconds on hand antisepsis. Nonetheless, any revision of EN 1500 should proceed cautiously to ensure antimicrobial efficacy, emphasizing complete hand coverage and strict adherence to technique.