Researchers Test Volume of Alcohol-Based Handrubs Needed to Fulfill Efficacy Standards

With some alcohol-based handrubs a volume of 1.1 mL is recommended per application but it is unknown if such a small volume is sufficient to cover both hands and if it fulfills current efficacy standards. Kampf and Ruselack, et al. (2013) sought to determine hand coverage of three handrubs (one gel based on 70% ethanol, one gel based on 85% ethanol, one foam based on 70% ethanol) applied with various volumes (all products: 1.1 mL, 2 mL, 2.4 mL, 1 push and 2 pushes; only foam product: 1.1 mL foam, 2 mL foam, 2.4 mL foam).

Fifteen subjects applied each product, supplemented with a fluorescent dye with each volume. Quality of coverage was determined under UV light. The efficacy of the three handrubs was determined according to ASTM E 1174-06 and ASTM E 2755-10. The hands of 12 subjects per experiment were artificially contaminated with Serratia marcescens and the products applied as recommended (1.1 mL for the products based on 70% v/v ethanol; 2 mL for the product based on 85% w/w ethanol). The log10-reduction was calculated per product.

A volume < 2 mL yielded a high rate of incomplete coverage (76% - 87%), a volume 2 mL revealed better results (18% - 40%). There was a significant difference between the five volumes used with all handrubs (p < 0.001; analysis of variance) but not between the three hand rubs themselves (p = 0.442). Application of 1.1 mL of the handrubs based on 70% ethanol yielded a log10-reduction of 1.85 or 1.60 log10 (ASTM E 1174-06) and failed the FDA efficacy requirement. Application of 2 mL of the handrub based on 85% ethanol reduced the contamination by 2.06 log10 (ASTM E 1174-06) and fulfilled the FDA efficacy requirement. Similar results were obtained according to ASTM E 2755-10.

The researchers say their data indicate that handrubs based on 70% ethanol and recommended with a volume of 1.1 mL per application are not suitable to ensure complete coverage of both hands and do not fulfill the current ASTM efficacy standard requirements. They add that infection preventionists should try to ensure patient safety by not reducing the volume of handrub required for adequate hand disinfection.
Reference: G Kampf, S Ruselack, S Eggerstedt, N Nowak and M Bashir. Oral presentation O007 at the 2nd International Conference on Prevention and Infection Control (ICPIC 2013): Lesser and lesser the impact of small volumes in hand disinfection on quality of hand coverage and antimicrobial efficacy. Antimicrobial Resistance and Infection Control 2013, 2(Suppl 1):O7 doi:10.1186/2047-2994-2-S1-O7