Your fecal lactoferrin came back positive. Now what?

If you're reading this late at night with the report open, start here. A positive result has several possible causes, and the test cannot tell them apart. What it did was tell your doctor that something in your gut is inflamed and worth a closer look.

For the basics of how the test works, see what the lactoferrin stool test measures. This page is about the result you actually have.

Does a positive result mean cancer?

No. The test was designed to spot inflammation, and doctors do not use it to screen for bowel cancer.

There is one finding you may come across, so here it is plainly. A 2024 study of 104 patients in Japan found lactoferrin levels tended to run higher in people with bowel growths, including cancer, than in healthy people. But in the same study, a test for hidden blood in stool did the better job of finding cancer. That is the kind of test used for bowel cancer screening. Lactoferrin rises with many kinds of gut trouble, so a positive result on its own cannot point to any one of them.

What can make the test positive

The lab is detecting lactoferrin, a protein carried inside white blood cells. When those cells gather in the lining of your intestines, some of them break down and the protein ends up in your stool. ARUP, one of the large US reference labs, describes a positive result as a marker for white blood cells in the stool, and nothing more specific than that.

Several things can bring those cells in:

• A gut infection. Bacteria, viruses and parasites all set off this response. A 2015 review found stool markers like lactoferrin help alongside other tests, but cannot diagnose an infection alone. If your symptoms started suddenly, your doctor may order a stool culture or a panel that looks for germs directly.
• Inflammatory bowel disease. That means Crohn's disease or ulcerative colitis, where the immune system keeps the bowel lining inflamed over months or years. Telling these apart from irritable bowel syndrome (IBS) is one of the main reasons the test gets ordered.
• Other kinds of inflammation. The test reacts to inflammation itself, whatever its source. It cannot say where in the intestines it is, or why.

How much one result can tell you

Less than it might seem, and that is worth knowing before you assume the worst.

When researchers pooled studies on telling IBS apart from inflammatory bowel disease in adults, only two lactoferrin studies met their standards. They concluded that lactoferrin on its own was of little clinical use for that job. Calprotectin, a similar stool test, and a blood test called C-reactive protein did better. That is one reason your doctor may repeat the workup with a different test before drawing any conclusion.

Results can also mislead in the other direction. ARUP's own guidance says a negative result does not rule out inflammation.

If you already have Crohn's disease or colitis

Here the test has a different job: checking whether your disease is active. A 2020 analysis combined 10 studies covering 773 people with inflammatory bowel disease.

For ulcerative colitis, the test caught active disease in about 8 of every 10 people who had it. It also came back negative for about 8 in 10 people whose disease was quiet. For Crohn's disease it caught active disease about as well, but only about 7 in 10 people with quiet disease tested negative. Put plainly, for 2 or 3 people in 10 whose Crohn's is under control, the test still reads positive.

So a single positive result during treatment does not prove a flare. Your gastroenterologist will weigh it against how you feel and, often, other tests.

Questions to take to your appointment

You don't need to know what your result means before you go. You need to leave knowing what happens next. These questions help:

• Why did you order this test, and what were you looking for?
• Does my lab report a number, or only positive or negative?
• Could an infection explain this? Do I need a stool culture?
• Would a calprotectin test or a blood test add anything?
• Do I need a colonoscopy, and if so, how soon?
• What symptoms should make me call before then?

Bring the printed report, so whoever reads it can see exactly which test the lab ran and how it reported the result.