I'm working on a protocol for DBS screening, using the method outlined in a poster by Thermo using 70% ethanol to clean the manual punch inbetween samples, I'm seeing a lot of carry over between samples. We're using the Uni-core manual punch. UPDATE: Punching clean filter cards 4 times inbetween samples also did not eliminate sample carry over.
Other than bleach and autoclaving inbetween samples, does anyone recommend another protocol for cleaning a manual punch to minimize or prevent sample contamination?
Blair Schneider
Susan Gurney
So far it does not appear so. I spiked fresh whole blood with a known bacterial source to determine this. I spiked using multiple concentrations so I could see if a "high level" spiked sample was processed, the punch cleaned, and then a "low level" spiked sample was processed. I did not see a change in Ct in a few preliminary runs of the low spiked. However, we are screening patient samples and are concerned we would potentially identify false positives.I plan on processing a "high level" spiked sample today, followed by a negative blood sample to see what happens.
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