Fecal Occult Blood Testing
Let’s start with some basic concepts. By definition, occult GI bleeding is hidden or unseen. It may be surprising…but we all lose blood through our GI tract daily, as is shown in this plot of the distribution of fecal blood levels quantified by HemoQuant on specimens from 1000 consecutive asymptomatic Mayo Clinic patients. As you can see, occult bleeding is not present or absent….but rather occurs along a continuum from normal physiologic bleeding to abnormal bleeding. This “physiologic” blood loss averages less than 2mL/day. Levels above a 2mL/day threshold occur in 5% and are considered abnormal. If blood loss chronically exceeds 5mL/day, iron deficiency ensues. So, at what level does bleeding become visible or overt?
Occult Gastrointestinal (GI) Bleeding: Definition
Jump to section:
- Occult Gastrointestinal (GI) Bleeding: Definition
- Quantity of GI Bleeding Required to "See" Blood in Stool
- Fecal Occult Blood Tests
- Why Detect Occult GI Bleeding?
- Causes of Fe Deficiency in Industrialized Countries (Average %)
- Causes of Occult GI Bleeding
- Fecal Detection of Ingested Blood
- Iron Deficiency or Anemia: Which Test?
- CRC Screening: Target Lesions
- Occult Bleeding From Colorectal Cancer
- Fecal Blood Testing for Colorectal Cancer (CRC)
- FOBT Screening
- Stool Test Detection of CRN in Screen Setting
- Laboratory Testing vs Office Digital Rectal Exam (DRE)
- Evaluation of Fecal Immunochemical Testing (FIT) Assays
- FIT Specificity
- CRC Screening by FOBTs
- CRC Screening Guidelines*
- CRC Screening: Which Fecal Blood Test?
- Soft Indications for FOBT Use?
- Fecal Occult Blood Tests Summary
- Mayo Medical Laboratories Tests