Biomarkers and Algorithm

The multitarget stool DNA (mt-sDNA) test is a colorectal cancer (CRC) screening modality that can detect 11 distinct biomarkers and uses an algorithm to provide a qualitative result.1-3 A positive result may indicate the presence of CRC or advanced adenoma (AA) and should be followed by a colonoscopy.2

mt-sDNA Biomarkers/Algorithm Download

Additional information on the biomarkers and algorithm utilized in the mt-sDNA test:

mt-sDNA Algorithm and Biomarkers Download

The mt-sDNA test uses advanced technology based on combined results of distinct biomarkers and hemoglobin to detect CRC and AA2

Doctor

A positive result may indicate the presence of CRC or AA and should be followed by a colonoscopy2

Multiple biomarkers are entered into an algorithm to determine a composite score, and a negative result is a composite score less than 183; a positive result is a composite score greater than or equal to 1831,a

mt-sDNA ALGORITHM1,b

Methylation markers
(strand counts)		 KRAS mutation markers
(strand counts)		 Hemoglobin
BMP3 NDRG4 ß-actin (ACTB ANB) KRAS1 KRAS2 ß-actin (ACTB KRAS) Fecal Hb ng/mL
STEP 1 Logistic score Apply weighting factors and combine (for BMP3, NDRG4, ACTB ANB, KRAS1, and KRAS2 strand counts and fecal Hb ng/mL)

Logistic score regression formula → Logistic score
STEP 2 Sum of scores DNA marker scores = Either “0” or "10" depending on whether the DNA marker is below ("0") or above ("10") the 99.5 percentile of normal

Sum of scores = logistic score + BMP3 score + NDRG4 score + KRAS1 score + KRAS2 score
STEP 3 Composite score Sum of scores subjected to an exponential equation → Range of values from 0 to 1000
RESULT
Negative result: Score <183 Positive result: Score ≥183
  • Multiple genetic markers (strand counts) and hemoglobin are scored1
  • A logistic score that applies weighting factors is added to other marker scores to determine the composite score1
  • The mt-sDNA test is qualitative, only providing a dichotomous "positive" or “negative” result1
  • A negative result is a composite score less than 183; a positive result is a composite score greater than or equal to 183.1 The composite score is not linear; a higher score does not implicate a stronger positive result1,2
  • The algorithm provides needed context to determine the test result and associated risk1

11 Distinct Biomarkers Produce a Qualitative Result1-3

The image displays 11 distinct biomarkers involved in molecular and hemoglobin assays associated with the algorithm for producing a qualitative result, negative or positive, with the Cologuard® test. Molecular assay, hemoglobin assays, and associated markers, including two DNA methylation biomarkers, 7 DNA mutation biomarkers, a DNA biomarker, and a fecal hemoglobin biomarker, are shown on the left. An algorithm is visible on the right and shows either a negative result indicating a decreased chance of CRC and advanced precancerous lesions or a positive result indicating an increased chance of CRC and advanced precancerous lesions.
  • Biomarkers do not have individually validated reference ranges, and each marker’s clinical significance is influenced by the other markers1,2
  • Therefore, biomarker levels cannot be interpreted separately, and the algorithm must incorporate all biomarker measurements to produce a result1,2
  • A positive result indicates that the biomarker combination has an increased association with CRC or AA1,2
  • Any positive result should be followed by a colonoscopy1,2

A Single Stool Sample Can Provide Evidence Of CRC And Precancerous Growth4

Illustrated cross-section of the colon showing progression of colorectal cancer from precancerous growth to stage 4 cancerous growth. Accompanying text within the image says blood is intermittently released into the stool and that DNA biomarkers are continuously shed into the stool.

As stool progresses through the colon and rectum, DNA sloughs from the lining of the colon and rectum as well as any blood that may be present1,3,5

  • This abnormal DNA and blood serve as the biomarkers evaluated by the test1,5
  • A single stool sample can present a snapshot of potential precancerous adenomas and colorectal carcinomas along the colon and rectum1,5

Learn more about the full Indications/Contraindications for the mt-sDNA test. Please see complete prescribing information for the Cologuard® test in the Cologuard Clinician Brochure.

Related Topics

Footnotes

  1. The composite score is not linear; a higher score does not equal more risk above the 183 cutoff value.1
  2. ACTB is a reference gene for quantitative estimation of the total amount of human DNA in each sample.2

List of definitions

AA: advanced adenoma; ACTB: β-actin; ANB: gene panel of ACTB, NDRG4, and BMP3; BMP3: bone morphogenetic protein 3; CRC: colorectal cancer; Hb: hemoglobin; KRAS: v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog; mt-sDNA: multitarget stool DNA; NDRG4: N-myc downstream-regulated gene 4.


References

  1. Imperiale TF, Ransohoff DF, Itzkowitz SH, et al. Multitarget stool DNA testing for colorectal-cancer screening. N Engl J Med. 2014;370(14):1287-1297.
  2. Cologuard Clinician Brochure. Exact Sciences Corporation. Madison, WI.
  3. Anand S, Liang PS. A practical overview of the stool DNA test for colorectal cancer screening. Clin Transl Gastroenterol. 2022;13(4):e00464.
  4. American Cancer Society. Colorectal Cancer Facts & Figures 2023-2025. Atlanta: American Cancer Society, Inc. 2022.
  5. Ahlquist DA. Multi-target stool DNA test: a new high bar for noninvasive screening. Dig Dis Sci. 2015;60(3):623-633.