A PBMC-based assay detects residual pro-inflammatory response in endoscopes after high-level disinfection undetected by ATP bioluminescence: a pilot study.

Gastrointestinal endoscopes require high-level disinfection (HLD) between uses, yet their complex internal architecture poses significant challenges for effective reprocessing. Conventional monitoring tools, particularly ATP bioluminescence, have limited sensitivity to detect residual pro-inflammatory molecules that may persist after reprocessing. This study evaluated a peripheral blood mononuclear cell (PBMC)-based inflammatory stimulation assay alongside ATP bioluminescence to assess endoscope reprocessing efficacy. Twenty-seven gastrointestinal endoscopes were reprocessed under three protocols: Standard HLD, HLD without brushing, and HLD without bedside flushing. Water samples were collected after bedside flushing, after manual cleaning, and after automated endoscope reprocessor (AER) processing. ATP levels declined substantially across all reprocessing stages but showed no statistically significant inter-group differences, reflecting the limited discriminatory capacity of bioluminescence in this setting. In contrast, IL-1β mRNA expression in PBMC cultures stimulated with endoscope water samples revealed persistent pro-inflammatory responses in endoscopes reprocessed without brushing or bedside flushing. After manual cleaning, IL-1β expression returned to baseline in Standard HLD, while remaining significantly elevated in both modified protocols. Residual pro-inflammatory response was still detectable after AER completion in these groups, with a 1.3-1.6-fold induction above sterile water control levels (q = 0.0106 and q = 0.0125, respectively), whereas Standard HLD endoscopes showed no significant difference from controls. These preliminary findings suggest that the PBMC-based assay may offer greater sensitivity than ATP bioluminescence for detecting residual pro-inflammatory responses associated with reprocessing critical step omissions. This pilot study supports the potential of PBMC-based assays as an audit tool in endoscope reprocessing, pending validation in large-scale multicentre studies.