Reliability testing for portable adenosine triphosphate bioluminometers

Measurement of adenosine triphosphate (ATP) using portable bioluminometers has been adapted from the food manufacturing sector, and it has been suggested that it could be used as an indicator of surface soiling or cleanliness in hospital settings.1 Some healthcare authorities are considering the use of portable ATP bioluminometers as a tool for standard setting for surface cleanliness to improve cleaning standards.2 Central to this approach is the use of a commonly accepted level of detected ATP"”expressed as relative light units (RLUs)"”that may be used as a surrogate for underlying soiling, including the presence of pathogenic microorganisms.3 It has been demonstrated that improvements can be made to cleaning processes with fluorescent markers through a simpler approach that provides a qualitative efficiency measurement of the cleaning process.4 Measurement of surface hygiene using ATP bioluminometers is thought to provide a more quantitative surrogate of surface cleanliness.5 A proposed ATP/RLU standard for acceptable cleanliness has been revised from 500 RLUs, originally suggested by Griffith et al,1 to 250 RLUs by Lewis et al6 and most recently to 100 RLUs by Mulvey et al.7 However, a close examination of the references reveals that different brands of ATP bioluminometers were used to establish the data in each reference"”a substantial problem given that each unit reads on a different relative scale.8 Even with a single branded unit variable results are observed without a clear explanation.9 There also is debate over the validity of using ATP measurement as an analogue for surface soils and the presence of pathogenic microorganisms.10 Our aim was to validate the reliability of measurement of 3 commonly available brands of portable ATP bioluminometers. Two of the brands selected (Hygiena and 3M) feature prominently in the published literature, and the third brand (Kikkoman) provided a different approach to luciferase presentation (a powder rather than a preprepared liquid).