Comparing adenosine triphosphate (ATP) luminescence technology to contact plate-based microbiologic sampling for the assessment of cleanliness of the patient care environment

Background: Adenosine triphosphate (ATP) luminescence technology is increasingly used in hospitals to monitor the cleanliness of the patient care environment; however, microbiological data to support the cut-off values used to determine if a surface “passes” or “fails” a cleanliness test are limited. We examined the relationship between ATP concentration and bacterial burden on environmental surfaces in the hospital.

Methods: Adjacent surfaces in occupied patient rooms and other patient care areas within an acute care hospital were sampled using two techniques: ATP burden in luminescence relative light units (RLU) using the 3M CleanTrace Hygiene Management System and bacterial burden in colony forming units (CFU) per cm² using BD BBL™ Rodac contact plates. Plates with >200 CFU were considered too numerous to count and recorded as 200 CFU for analysis. To assess the relationship between RLU and CFU, Spearman and Pearson correlations were calculated and a negative binomial model was selected. To determine an appropriate RLU cut-off value, logistic regression and an ROC curve were completed.

Results: 98 surfaces were sampled. The median RLU value was 372 (13-139,021) and median CFU count was 0.7 colonies per cm² (0-7.8). The Pearson and Spearman correlations between CFU and log-transformed RLU were 0.23 and 0.30, respectively. Under the negative binomial model, RLU was a statistically significant predictor for CFU (p=0.0080). In this model, if the RLU value increased 100%, the mean CFU count increased 15.7%. The ROC curve determined that the best cut-off value for RLU is 384 (between 379 and 394); however, the area under the curve was 0.63.

Conclusion: While ATP luminescence technology monitoring is not equivalent to microbiologic testing of environmental surfaces, these findings suggest that a correlation exists between RLU and CFU and that surfaces for which sampling yields an RLU value of at least 384 RLU are more likely to have a positive bacterial culture (≥1 CFU/cm²).Thus, given its ease and rapid turnaround time, ATP luminescence technology may serve as a useful marker of cleanliness that can provide real time data to allow immediate feedback to persons responsible for cleaning the hospital environment.