Intra-laboratory reproducibility of the hand hygiene reference procedures of EN 1499 (hygienic handwash) and EN 1500 (hygienic hand disinfection).

The bactericidal efficacy of hand antiseptic products is determined in Europe using two norms--EN1499 (hygienic handwash), and EN 1500 (hygienic hand disinfection) based on reducing the counts of bacteria on artificially contaminated hands. Each requires 12-15 data sets per test and comparison with a reference procedure. Recent research using EN 1500 suggested that most alcohol-based hand gels are significantly less effective than the reference alcohol (2-propanol 60%), whereas liquid alcohol-based rubs are not. However concerns about the accuracy and reproducibility of the norm reference procedures have been raised. We therefore analysed 23 experiments carried out using EN 1500 representing 342 hand disinfection procedures, and 12 experiments using EN 1499 representing 178 handwashes, all performed in the same laboratory for reproducibility of the reference procedures. The reference alcohol gave a mean log(10) reduction factor (RF) of 4.64 +/- 0.93; only one data set gave a significantly higher result (5.14, P = 0.034), and one significantly lower (4.05; P = 0.034). Analysis of all 23 means revealed no significant difference (P = 0.188; ANOVA model). The reference soap gave a mean reduction of 2.82 +/- 0.49. Two data sets were significantly higher than this (3.35,P < 0.001; 3.12, P < 0.001) and two significantly lower (2.55, P = 0.031; 2.47,P = 0.004). Analysis of all the means did reveal a significant difference (P < 0.001, ANOVA model), which is probably explained by the smaller standard deviations of these results. Pre-values (bacteria recovered from fingers before a reference procedure) correlated significantly with RFs for both hand disinfection (correlation coefficient: 0.291;P = 0.01) and handwash (correlation coefficient: 0.372, P = 0.01). Overall both procedures gave accurate and reproducible results.