ColoAlert – stool test for hidden blood and DNA markers

The immunochemical test for haemoglobin (iFOBT, also called FIT) detects human blood pigment in stool that cannot be seen with the naked eye – so-called occult blood. A value above the laboratory's reference range shows that, at the time of sampling, blood entered the gut somewhere in the lower digestive tract. More on the page Occult blood in stool.

The value does not say where the blood comes from. Common sources are haemorrhoids and small tears at the anus; in a study of almost 4,000 people, those with haemorrhoids more often had a positive stool test without an advanced finding at colonoscopy (PubMed 27873508). Inflammatory bowel disease, polyps or tumours can also bleed. A raised value is therefore assessed by a doctor, usually by colonoscopy – not by a second stool test.

In the blood, the transport protein haptoglobin binds free haemoglobin. This complex is considered more stable on its way through the gut than free haemoglobin, which can be broken down along the way. It is therefore measured as a second blood marker, especially with regard to bleeding from higher sections of the bowel.

In a study of 621 people before colonoscopy, the complex was more often abnormal in polyps than haemoglobin alone, but also more often in people without findings – it is more sensitive and at the same time less specific (PubMed 10663892; similar: PubMed 27413251). Like a raised haemoglobin value, a raised value indicates blood in the stool and is assessed by a doctor.

The lining of the gut renews itself constantly, and shed cells end up in the stool. The laboratory uses PCR to measure how much human DNA (hDNA) the sample contains. A larger amount may point to increased cell turnover or cell shedding.

In a small study, the amount of human DNA in stool was higher in people with colorectal cancer than in controls; there was no difference between people with polyps and controls (PubMed 26840470). Inflammation or blood in the stool can also increase the amount of DNA. The value is therefore a non-specific indication, not a statement about a particular disease, and is interpreted by a doctor only together with the other values.

KRAS and BRAF are genes that help control cell growth. Certain changes (mutations) in these genes are not inherited but arise during life in individual cells. KRAS mutations are among the most common genetic changes in tumours of the large bowel, pancreas and lung (PubMed 32725342). The BRAF mutation V600E is found in about 15 out of 100 non-hereditary bowel tumours and occurs early in a development pathway that runs via so-called serrated (saw-tooth) polyps (PubMed 30598662).

The laboratory looks for these changes in cell DNA from the stool. A positive result means: DNA with such a change was found in the sample. It does not say where it comes from, whether a precursor, a polyp or something else lies behind it, and it is not a diagnosis. A positive mutation result is an indication that must be assessed by a doctor, usually by colonoscopy. A case report describes how a positive KRAS result led to a second colonoscopy in which a previously missed polyp was removed (PubMed 38213210) – a single case, not evidence of the test's performance.

The report lists each value with the laboratory's reference range: the three quantitative values (haemoglobin, haemoglobin-haptoglobin complex, human DNA) as numbers, the two mutations as "positive" or "negative". So you can see which values are within the reference range and which are not.

If one of the values lies outside, the result counts as abnormal and is an indication that should be assessed by a doctor. How much weight a single value carries in your situation is something to discuss with the ORY expert team or with your doctor or naturopath, for example from the ORY expert network. ORY does not provide its own rating or risk calculation beyond the laboratory's information.

ColoAlert is a laboratory test from a stool sample that you collect at home. It combines two approaches: an immunochemical test looks for hidden blood (haemoglobin and haemoglobin-haptoglobin complex), and a DNA analysis measures the amount of human DNA and looks for mutations in the KRAS and BRAF genes. The test comes from the manufacturer Mainz Biomed and is analysed in a partner laboratory in Germany.

The result is an indication of possible changes in the gut that need to be assessed – not a diagnosis. Whether a change is present and what it is can only be shown by a medical examination, usually a colonoscopy with tissue sample.

The main study on ColoAlert is a multicentre study of 734 people who were about to have a colonoscopy or surgery (Dollinger 2018, PubMed 30336540). Compared with colonoscopy, the combined test was abnormal in 85 out of 100 people with colorectal cancer; in 92 out of 100 people without findings at colonoscopy it was normal. Put the other way round: some tumours were missed (false negative), and about 8 out of 100 people without findings still had an abnormal result (false positive).

These figures should be read with caution. A European assessment (EUnetHTA) rated the certainty of the data as low to very low: an earlier version of the test was studied, reliable data on precursors (advanced adenomas) are lacking, there are no studies on the effect on disease or death rates, and stool DNA tests failed more often because of the sample than simple faecal blood tests (PubMed 37426885). The assessment recommends a screening study with the current product version.

The immunochemical stool test (iFOBT) of the statutory bowel cancer screening programme in Germany only measures haemoglobin, i.e. hidden blood. ColoAlert additionally measures the haemoglobin-haptoglobin complex, the amount of human DNA and KRAS and BRAF mutations. Polyps and precursors often do not bleed, or only intermittently; in a review of 46 studies, the sensitivity of iFOBT for advanced precursors was only about 21 to 31 out of 100, depending on the threshold (PubMed 31472152). The DNA markers are meant to complement this.

Important for context: the iFOBT is part of an evaluated programme with fixed intervals and an entitlement to colonoscopy after an abnormal result, and it is free of charge for people with statutory health insurance in Germany from the age of 50. There are no comparable programme data for ColoAlert (see the question on test performance). The additional markers also mean more opportunities for a false positive result.

No. Colonoscopy is the examination in which doctors look directly at the lining of the bowel, take tissue samples and can remove polyps in the same session. A stool test cannot do this. It can only give an indication that a colonoscopy is needed.

The test also does not replace the statutory bowel cancer screening programme in Germany. According to the Federal Joint Committee (G-BA), people with statutory health insurance aged 50 and over are entitled to two colonoscopies at least ten years apart or, alternatively, an immunochemical stool test every two years; since April 2025 this applies equally to women and men. With a family history, an earlier start may make sense – discuss this with a doctor.

No. A normal result does not rule out changes in the gut. In the main study, some tumours were missed (PubMed 30336540), and there are no reliable data for precursors (PubMed 37426885). Polyps often do not bleed and do not always shed DNA with the mutations looked for.

A normal result is therefore no reason to skip the colonoscopy or the stool test of the statutory bowel cancer screening programme, or to leave complaints unassessed.

The following complaints and causes are linked in research with blood in stool or with changes in the large bowel:

• Visible blood in stool or on toilet paper: in a systematic review of primary care, rectal bleeding in people aged 50 and over was the symptom with the highest predictive value for colorectal cancer; the authors recommend that it should always be investigated (PubMed 21619747). Well established.
• Anaemia, especially iron deficiency anaemia: in about a third of men and postmenopausal women with iron deficiency anaemia, a cause is found in the digestive tract; the British guideline provides for examination of the stomach and bowel (PubMed 34497146). Well established.
• Changed bowel habits and unintended weight loss: together with bleeding they increase the likelihood of a finding; abdominal pain, diarrhoea or constipation alone are of little value (PubMed 21619747). Observed in studies.
• Haemorrhoids and anal fissures: common, mostly harmless sources of blood in stool and a known cause of false positive stool tests (PubMed 27873508). Well established.
• Inflammatory bowel disease such as Crohn's disease or ulcerative colitis: found in a small proportion of people with a positive stool test in a screening programme (PubMed 39362990). As a marker of inflammation in stool, calprotectin is more commonly measured. Observed in studies.
• Diverticula and diseases of the rectum and anus: the most common causes of bleeding from the lower digestive tract (PubMed 38670052). Well established.

Associations from studies describe groups, not the cause in an individual. The test does not explain complaints and does not make a diagnosis; persistent complaints should be assessed by a doctor first.

With the following warning signs, the first step is a doctor's practice, not a stool test. Testing and waiting for the result loses valuable time here:

• visible blood in stool, black stool or bleeding from the anus
• changed bowel habits over several weeks, such as a new alternation of diarrhoea and constipation or pencil-thin stool
• unintended weight loss, night sweats or persistent exhaustion
• anaemia or iron deficiency without an explaining cause
• persistent abdominal pain or a palpable lump in the abdomen
• colorectal cancer or bowel polyps in parents, siblings or children – then clarify with a doctor from what age a colonoscopy makes sense

In case of heavy bleeding, circulatory problems or severe abdominal pain, call the emergency number 112.

An abnormal result is an indication, not a diagnosis. The next step is a medical consultation and usually a colonoscopy. Many abnormal stool tests have harmless causes; whether that is the case, however, only the examination can show.

Do not wait long with the assessment: a systematic review found consistently worse outcomes with longer waiting times to colonoscopy after a positive stool test (PubMed 33010414). Discuss the report with the ORY expert team or with your doctor or naturopath, for example from the ORY expert network; for the colonoscopy you need a medical referral. Whether health insurance covers the colonoscopy is something to clarify at the practice.

The measured values are not targets to be lowered. They are indications of whether something in the gut needs to be assessed. An abnormal value is not clarified by diet, supplements or a repeat test, but by a doctor.

ORY does not give dietary, supplement or therapy recommendations for this test. What a result means for you and which examination makes sense next is something to discuss with the ORY expert team or with your doctor or naturopath, for example from the ORY expert network.

According to the laboratory's instructions:

• Collect the stool with the enclosed stool catcher; it must not come into contact with toilet water.
• Do not collect during menstruation.
• Postpone collection in case of acute gastrointestinal complaints or open haemorrhoidal bleeding – both can distort the blood test.
• Fill the tube for the DNA analysis (brown cap) with a pea-sized amount only; overfilled tubes are rejected. Do not pour out the liquid in the tube.
• Insert the sampling stick of the two tubes for the blood test only once; inserting it several times can lead to a false positive result.
• Collect in the morning if possible and send Monday to Thursday, not before weekends or public holidays.

The report is usually available 7–21 days after the sample arrives at the laboratory, not from the date of order. You will be notified as soon as it is ready. A consultation on the report with the ORY expert team is included.

ColoAlert costs €250 at ORY, including test kit, return shipping, laboratory analysis and results consultation. Statutory health insurance in Germany usually does not cover the test.

Free of charge for people with statutory health insurance, on the other hand, is the statutory bowel cancer screening programme: from the age of 50, two colonoscopies at least ten years apart or, alternatively, an immunochemical stool test every two years (Federal Joint Committee (G-BA)). Private health insurers reimburse laboratory tests fully, partly or not at all depending on the contract; how this works at ORY is described in the section on reimbursement.

For people with statutory health insurance aged 50 and over, the insurance programme is the first route: colonoscopy or immunochemical stool test, free of charge and with regulated follow-up. With warning signs, the first step is a doctor's practice, not a test. ColoAlert is a self-paid additional test for blood and DNA markers in stool.

If your question is not about blood and DNA markers but about gut flora, gut barrier or digestion, these are different questions with different tests:

• Gut profile microbiome & gut barrier (€315): gut flora, zonulin, sIgA, digestion markers
• Basic gut profile (€285): microbiome, leaky gut and histamine
• Helicobacter pylori stool test (€65): antigen of the stomach bacterium

Which test suits your question can be clarified in the free initial consultation with the ORY expert team or with your doctor or naturopath, for example from the ORY expert network.