How long is enough? Identification of product dry-time as a primary driver of alcohol-based hand rub efficacy

Abstract

BackgroundThe World Health Organization has called for the development of improved methodologies to evaluate alcohol-based handrub (ABHR) efficacy, including evaluation at “short application times and volumes that reflect actual use in healthcare facilities”. The objective of this study was to investigate variables influencing ABHR efficacy, under test conditions reflective of clinical use.MethodsThe test product (60% V/V 2-propanol) was evaluated according to a modified EN 1500 methodology, where application volumes of 1 mL, 2 mL, and 3 mL were rubbed until dry. Statistical analyses were performed to investigate the relative influences of product volume, hand size, and product dry-time on efficacy, and hand size and hand contamination on product dry-time.ResultsMean log10 reduction factors (SD) were 1.99 (0.66), 2.96 (0.84) and 3.28 (0.96); and mean dry-times (SD) were 24 s (7 s), 50 s (14 s), and 67 s (20 s) at application volumes of 1 mL, 2 mL, and 3 mL, respectively (p ≤ 0.030). When data were examined at the individual volunteer level, there was a statistically significant correlation between dry-time and log reduction factor (p < 0.0001), independent of application volume. There was also a statistically significant correlation between hand surface area and dry-times (p = 0.047), but no correlation between hand surface area and efficacy (p = 0.698).ConclusionsWhen keeping other variables such as alcohol type and concentration constant, product dry-time appears to be the primary driver of ABHR efficacy suggesting that dosing should be customized to each individual and focus on achieving a product dry-time delivering adequate efficacy.

Hand hygiene behavior among Sri Lankan medical students during COVID-19 pandemic

“…The participants scored noticeably low on the correct procedure of hand hygiene using alcohol hand rub, tested on many dimensions such as drying time and concentration of alcohol. Appropriate alcohol concentration and drying time are the primary drivers of efficacy [ 11 ]. It is essential to understand that efficacy also depends on the alcohol quantity applied.…”

Systematic review on factors influencing the effectiveness of alcohol-based hand rubbing in healthcare

“…As shown in Tables 1 , 2 and 3 , this included two parallel design [ 16 , 17 ], one crossover [ 18 ] and eight within-subject [ 19 – 26 ] RCTs, and one parallel design [ 27 ], one crossover [ 28 ] and seven within-subject [ 29 – 35 ] NRTs. Apart from one study [ 17 ] conducted in China, all included evidence derives from high income countries, including Australia (n = 1) [ 28 ], Austria (n = 2) [ 25 , 33 ], France (n = 1) [ 31 ], Germany (n = 3) [ 16 , 18 , 32 ], Switzerland (n = 5) [ 23 , 24 , 26 , 29 , 30 ], UK (n = 3) [ 27 , 34 , 35 ] and USA (n = 2) [ 19 , 22 ], while two were multisite studies conducted in the Netherlands and UK [ 21 ], and in Germany and USA [ 20 ]. Despite searching for studies published since 1980, the publication year of the included studies ranged from 2003 to 2020, with most studies (n = 15) published within the last 10 years.…”

“…60% (v/v) isopropanol; 2. 80% (v/v) ethanol + 1.45% (v/v) glycerol + 0.125% (v/v) hydrogen peroxide (each in liquid, gel & foam format) Application technique 6-steps; Mean drying times (seconds) , for 2 tested ABHRs in 3 formats) 1.5 ml: 19.67–31.53 3 ml: 35.07–63.13 Increasing the volume increased the drying time (P < 0.001) Jain, Clezy & McLaws (2018) [ 28 ] Australia Crossover NRT Clinical 40 HCWs 2 dispenser pump presses vs. 3 dispenser pump presses Bacterial load on hands Fingertips (cultured for MRSA and VRE) Product foam ABHR; product contents not reported Application time rubbed until hands were dry Application technique 6-steps Number of plates with MRSA or VRE growth: 2 dispenser pumps: 2/40 grew 1 colony-forming unit of MRSA 3 dispenser pumps: No growth Suchomel et al (2018) [ 33 ] Austria Within-subject NRT Laboratory 15 volunteers 1ml 2 ml 3 ml 1) Bacterial load on hands; 2) Hand size; 3) Drying time 1) Fingertips; 2) Hand surface area calculation Small < 375cm 2 Medium 376–424 cm 2 Large > 425 cm 2 ; 3) Time measured until participants reported that their hands felt dry Product ABHR 2-propanol 60% (v/v) liquid; Application time not applicable (drying time measured as outcome) Application technique 6-steps Artificial contamination ( E. coli ) Mean log 10 RF (SD) 1ml: 1.99 (0.66) 2 ml: 2.96 (0.84) 3 ml: 3.28 (0.96) Mean log 10 RFs were greater when larger volumes were used (P < 0.0001), but no significant difference between 2 ml & 3 ml (P = 0.08) Hand size and log 10 RF (P = 0.698). Hand size and RF accounting for dry-times and volumes (R 2 = 77%, P = 0.403) Mean (SD) drying (seconds) 1ml 24 (7) 2 ml 50 (14) 3 ml 67 (20) (P ≤ 0.030) Mean drying times were greater when larger application volumes were used (P < 0.0001) Regardless of volume Reduction fraction increased 0.29 log 10 per 10 s increased drying time Kenters et al (2020) [ …”

“…The studies within the Volume of ABHR category were further grouped into four sub-categories, based on the outcome measure, including the sub-category of studies that accounted for hand size. Therefore, the sub-categories included the influence of ABHR volume on: bacterial load reduction (n = 8) [ 17 , 19 , 25 , 28 , 29 , 32 – 34 ]; bacterial load reduction with consideration of hand size (n = 4) [ 29 , 32 – 34 ]; drying time (n = 8) [ 17 , 20 – 22 , 25 , 33 – 35 ] and hand surface coverage (n = 6) [ 19 – 21 , 27 , 31 , 32 ]. Furthermore, most studies included in the Volume of ABHR category focused on more than one outcome measure.…”

Nursing preference for alcohol-based hand rub volume

“…1,2 One recent study found a linear relationship between dry-time and the log reduction of bacteria on hands that was independent of application volume. 3 Limited evidence suggests that there is considerable variation in the amount of ABHR that is used per application by health care providers.…”