LAUSR

to process blood specimens (whole blood, plasma, occasionally serum) to attempt the isolation and characterization of human adenoviruses (HAdVs) infecting pediatric trans-plant recipients, we have repeatedly been challenged by the high toxicity of these samples to cells in culture. Here, we share important lessons learned from troubleshooting this critical obstacle. After a couple of rounds of loss of all inoculated cultures without being able to determine why whole blood, and plasma specimens in particular (sometimes also urine and stool specimens), lifted cell monolayers on contact, we hypothesized two candidate sources of cell toxicity: patient medications and anticoagulants in the collection tube. We started thinking about the need to somehow clean up these irreplaceable samples and also researching the speci fi cations of blood collection tubes from various manufacturers. We rapidly learned that lavender top tubes (of any brand) that are regularly used for hema-tological testing provide a fi nal concentration of ; 1.8 mg K 2 EDTA per milliliter of blood as an anticoagulant (1). This concentration is 10 times higher than that of Versene, the EDTA solution widely used as a nonenzymatic cell dissociation reagent and formulated as 0.2 g/L EDTA(Na 4 ) in phosphate-buffered saline (PBS), explaining why plasma and EDTA-whole blood specimens were poorly — or not at all — tolerated by A549 cell monolayers in shell vials or culture tubes. Interestingly, we could not fi nd any reports of similar observations in the literature, only succinct descriptions of sample dilution before inoculation with no rationale or explanation provided.