Have you checked for “stranger things” in your automated dispensing system for PET radiopharmaceuticals ?

Many nuclear medicine departments are now equipped with automated dispensing systems for PET radiopharmaceuticals. Initial microbiological qualification is classically carried out by the manufacturer or the distributor once the equipment is installed, but the periodic qualification falls to the radiopharmacist. According to the GERPAC Methodologic guide for classified area qualification, this study aimed at setting up an initial and periodic qualification plan of the microbiological safety of Trasis® Unidose, whose monodose-filling, the critical step, implies an open system under ISO4.8.

Materials and methods

Both the environment and the process were assessed for microbiological contamination at the end of a session, repeated on 3 different days. Environment surfaces were checked on 3 different sites (ISO4.8 carousel, ISO7 gloves and ISO7 reservoir surface), through the application of 25 cm2 trypticase-soy (TS) agar, before and after biodecontamination (BD) following our internal procedures. Agars were incubated for 5 days (37°C, 5%CO2) and colonies were then counted (CFU/25cm²). The whole process sterility was evaluated through an adapted media-fill test, a sterile TS broth vial in place of the radiopharmaceutical, after BD. The resulting cartridges were aseptically transferred to TS broth tubes and placed for incubation for 5 days with daily monitoring of turbidity. Further identification was realized by our Microbiology Department.

Results and discussion

After the incubation period, a minor microbiological contamination was found on TS agars sampled from the carousel before BD and identified as classical hand-borne microflora (Micrococcus luteus and Staphylococcus sp.). After BD, all the agars were found sterile. The media-fill test resulted in clear, sterile cartridges, validating the process sterility. Investigating for the biocontamination origin, the cap reused daily for filter sealing tests was found contaminated (13 CFU/25cm2). We consequently adapted our BD procedure to include this instrument, and decided to brief our operators once a month on microbiological control results, hygiene and good practices. Our latest results show these corrective actions solved the biocontamination issue.

Conclusion

The automation of PET monodose conditioning process still implies human intervention for material preparation and manual BD, and needs initial and periodic qualification of the environment and the conditioning process, to meet the specifications. We therefore recommend a monthly microbiological control of surfaces and instruments and a half-yearly media-fill test. An initial and annual qualification of the operators has also been established. Regular training and information should be dispensed to the operators, regarding the importance of properly carrying out the BD of surfaces and instruments.

Watch the video in simultaneous translation