A study of three methods for assessment of hospital environmental cleaning

Background The environment is increasingly appreciated as a factor in healthcare associated infections. Several methods for measuring environmental contamination are available. Our goal was to compare quantitative microbiology to adenosine triphosphate (ATP) detection on a sample of hospital surfaces both pre-and post-cleaning, and to assess fluorescent marker results in the same rooms. Methods In a sample of 10 rooms, ATP readings by relative light units (RLU) and quantitative determination of colony forming units (CFU) were measured pre-and post-cleaning on 10 high-touch hospital environmental surfaces. Removal of fluorescent markers (FM) was evaluated post-cleaning in the same rooms. Methods were compared using correlational analyses. Results The ATP readings were usually higher than CFU readings compared with their respective norms for cleanliness. The direction of change in cleanliness assessment (usually down after cleaning) was consistent between the RLU and CFU methods. In addition, CFU and RLU values correlated pre-cleaning, but not post-cleaning. A receiver operating characteristic (ROC) curve suggested a 'clean' cutoff of 8RLU/cm2 for the ATP assay, higher than 2.5RLU/cm2 cutoff most often used. Neither method correlated well with FM results. Conclusions The methods for measuring environmental cleanliness have shown inconsistent correlation, but measure different parameters. Additional studies are needed to assess the correlation and predictive value of the three methods for room cleanliness assessment.