“If you have 100 bacteria in the voided samples and you have 50 bacteria in the catheterized samples, you assume that a lot of it from the cup is because of contamination,” says Laura Bukavina, MD, MPH.
In this video, Laura Bukavina, MD, MPH, discusses findings from the European Urology Focus paper, “Global Meta-analysis of Urine Microbiome: Colonization of Polycyclic Aromatic Hydrocarbon–degrading Bacteria Among Bladder Cancer Patients.” Bukavina is a urologic oncology fellow at Fox Chase Cancer Center in Philadelphia, Pennsylvania.
It is much easier to have a patient void into a cup than it is to ask them to catheterize for urine. A lot of studies that have been done even 10 years ago, even the ones that have been published in very high-impact journals, have used voided urine. And actually, some of the research later on—not in bladder cancer but in prostate cancer—has also used voided urine. What we found is that if you look at the samples and you compare them side to side - voided urine to patients who were catheterized—there is huge contamination [in the voided urine]. You'll find bacteria in the voided urine samples that are typical for the vagina or are typical for stool. And then when you look at the catheterized samples, the number of bacteria is almost half. So if you have 100 bacteria in the voided samples and you have 50 bacteria in the catheterized samples, you assume that a lot of it from the cup is because of contamination, whether it's fecal contamination or vaginal contamination. That's very important because people make assumptions on the presence of this bacteria with the disease. Because it's contaminated, and it's frequently contaminated with the same bacteria, and they continuously see it, then people make these assumptions that once we see these bacteria, it's associated with cancer, because we see it all the time. That's the wrong way to do this type of analysis. You have to be able to recognize what's contaminated and remove those contaminants. That was our first step. We looked at what the contaminants are, and we removed the majority of those contaminants and really focused on the bacteria that we were 100% sure were coming from the bladder.
This transcription was edited for clarity.