Human DNA (hDNA, stool)

Detection of human DNA in stool – it shows cell shedding from the intestinal mucosa. The amount can be raised with neoplasia, but also with inflammation or bleeding in the gut (a ColoAlert component).

What detecting human DNA in stool shows

The gut lining renews itself continuously: stem cells divide at the base of the crypts, the new cells migrate to the surface and are shed there after a few days. Most of the shed cells undergo orderly cell death, during which their DNA is broken into small pieces; enzymes in the gut and the gut bacteria break it down further. By far the largest part of the DNA in stool therefore comes from bacteria, and only a small part from the human body. The measured amount of human DNA reflects how many human cells, and how well-preserved DNA fragments, from the lining, from blood and from immune cells have reached the sample.

Low human DNA in stool – what does it mean?

A small amount of human DNA corresponds to the normal process: the lining cells are renewed at the usual pace, the shed cells die in an orderly way, and their DNA is largely broken down in the gut before it is excreted. At the same time the laboratory also uses the amount to check whether the sample contains enough human genetic material for the further DNA tests – for example for KRAS or BRAF mutations; how well the DNA is preserved until measurement also depends on how the sample is stored and transported.

High human DNA in stool – what is happening in the gut lining?

More human DNA reaches the stool when more cells detach or their DNA is broken down less. In studies, cells from growths in the lining detached more often and released longer, less fragmented DNA pieces more frequently, because they undergo orderly cell death less often. But other processes also raise the amount: with inflammation of the gut lining, immune cells migrate in and are excreted too; with bleeding, white blood cells enter the gut; and a damaged lining sheds more cells. A high value therefore shows an increased passage of cells into the gut, not its cause.

The interpretation is given in your report.