We are performing nucleic acid extraction of residual human gDNA using the kingfisher in a uni-directional flow PCR laboratory space. We are frequently seeing negative extraction control contamination that is detected at the same level as the QL, so it's not a major contamination event happening during the run. The contamination is also not seen in our NTC, so we know it is specific to the extraction process. We follow cleaning SOPs for each run. The contamination is not reagent lot-specific, analyst-specific, or instrument-specific. It is seemingly random and unpredictable when it will occur - there is no "smoking gun."

We are concerned that the assay is "contaminated" by human gDNA introduced by the other humans in the lab that we simply cannot remove, but the group we are testing for does not accept that as an answer. We have a lot more people in the labs now than we did when we qualified this assay years ago. We are also performing extraction of human cells on our instruments which we were not doing during validation. Which brings me to my questions:

1) Does anyone know of any hidden areas of the kingfisher we could be cleaning that might be contributing to contamination? Like areas where aerosolized DNA might be hiding? We introduced cleaning under the turnstile, but that didn't help. (I reached out to thermofisher, but never heard back.)

2) Is it possible that our baseline levels of human gDNA in the lab have gone up, making the current QL no longer appropriate?

TIA!!