SURGICAL HAND DISINFECTION WITH ALCOHOLS AT VARIOUS CONCENTRATIONS - PARALLEL EXPERIMENTS USING THE NEW PROPOSED EUROPEAN STANDARDS METHOD

OBJECTIVES: To establish the concentration of isopropanol that exerts the same immediate and sustained effects as n-propanol 60% v/v in surg ical scrubbing, and to assess the performance of the test method propo sed as the European standard in parallel experiments. DESIGN: Isopropa nol at concentrations of 70%, 80%, and 90% v/v was tested in compariso n with n-propanol 60%, the proposed reference preparation, in the draf t method proposed by the European standard. A Latin square design was used with four balanced blocks of five volunteers each in four experim ental runs that were spaced by intervals of 1 week each. Volunteers we re allotted randomly to one of the four blocks. Independently, the vol unteers' right and left hands also were randomized into two groups for the assessment of either immediate or sustained effects. SETTING: Two laboratories supervised by two investigators, one from Vienna, Austri a, and one from London, The United Kingdom. METHOD: The release of ski n nora from the fingertips of clean hands was assessed before and afte r treatment by immediate sampling from one hand and by sampling of the other, gloved hand after 3 hours. The mean log(10) reductions (RF) of bacterial release achieved by rubbing the alcoholic preparations for 3 minutes onto the hands were established. RESULTS: For both experimen ts, the immediate effects of isopropanol 70% (RF, 2.0 and 2.1, respect ively) were significantly smaller than those of the reference n-propan ol 60% CRF, 2.4 and 2.6, respectively). This also was found with the s ustained effects (RF, 0.7 and 1.1 vs 1.0 and 1.6, respectively). At 90 %, isopropanol equalled the immediate effect of n-propanol 60%, wherea s at 80% it proved slightly (although not significantly) less active. There were no significant differences in the results of both investiga tors. The sustained effects of isopropanol 80% and 90% were both large r than the reference in Vienna but were found smaller by the London in vestigator; none of the differences were significant. Mean RFs were si gnificantly different between Vienna and London with n-propanol 60% an d isopropanol 70%, but not with isopropanol at 80% or 90%. CONCLUSIONS : At 90%, isopropanol is as effective as n-propanol 60%, which was pro posed by the European Committee for Standardization as a reference in testing products for surgical hand disinfection. It could, therefore, serve as an alternative if the proposed agent is undesirable for any r eason. In parallel experiments by two investigators, the proposed test method proved well workable; the results were very similar and the co nclusions identical (Infect Control Hosp Epidemiol 1998;19:778-781).