Automated Surface Swab Sampling: A Statistical Comparison of a Novel Approach to Existing Methods

Abstract

Analytical testing and an appropriate sampling method are instrumental in confirming that equipment surfaces have been adequately cleaned during cleaning validation or verification activities. The sampling method is critical to generating accurate results. Regulatory Health Authorities (RHAs) expect manufacturers to employ rinse, surface swab, or a combination of the two, with one favoring swab sampling methods. Surface swab sampling is performed manually by directly holding the swab (hand swabbing) or attaching the swab to the end of an extension pole (remote swabbing). Remote swabbing is an alternative for cases in which the equipment surfaces to be sampled are not readily accessible and would otherwise require confined space entry. This study evaluated the performance of a prototype automated swabbing device constructed from configurable microcontrollers, microelectronics, and electromechanical components against representative manual sampling methodologies. The automated swabbing device was designed and built to automate the swabbing work process for surfaces exhibiting various accessibility issues and challenges. Automated swab sampling of pharmaceutical manufacturing equipment offers several advantages over hand swabbing or remote swabbing, including decreased variability, the necessity for swab qualification of operators, increased accuracy versus remote swabbing, and decreased risk to personnel. To determine if automated swabbing can replace the current state of the art in manual swabbing, Hyde Engineering + Consulting performed a comparative analysis of manual swabbing methods, hand and remote, and an automated swabbing method using a prototype device developed by Swabbot Solutions. This case study evaluated the three swabbing methods using multiple replicates, concentrations, representative soils, and controls to gauge the relative recovery performance of the accuracy and variability of each method. The study showed that the automated swabbing device achieved recovery levels comparable to those of the hand swabbing method but with lower variability. The remote swabbing method exhibited higher variability and lower recovery levels statistically dissimilar to both the hand and automated swabbing methods. Based on these performance results, we concluded that an automated swabbing method is an acceptable alternative to hand swabbing and outperforms the remote swabbing method.