Considering Endoscopy in Iron Deficiency Anemia? Don’t Rely on Fecal Blood Testing to Decide
Douglas K. Rex, MD, FASGE, reviewing Lee MW, et al. Am J Gastroenterol 2020 Jan 10.
Fecal blood testing is approved as a colorectal cancer screening test. However, fecal blood testing is often used in clinical practice to triage patients with symptoms or laboratory findings into greater or lesser risk of diseases such as GI tract cancer and inflammatory bowel disease. For example, in young patients with nonspecific symptoms, the combination of negative fecal immunochemical testing (FIT) and normal fecal calprotectin has high negative predictive value for inflammatory bowel disease.
In a systematic review and meta-analysis identifying 22 studies, including 12 in iron deficiency anemia (IDA), 8 in ulcerative colitis (UC), and 2 in acute diarrhea, tests were variably performed with FIT or guaiac-based fecal occult blood testing (gFOBT).
Overall, the sensitivity of FOBT was 0.58 for causes of IDA at endoscopy, with similar results for FIT and gFOBT. Sensitivity in IDA patients was 0.83 for colorectal cancer (CRC) and 0.54 for non-CRC lesions. In ulcerative colitis, FIT had a sensitivity of 0.72 and specificity of 0.80 in predicting endoscopic activity in UC. In acute diarrhea, gFOBT had a sensitivity of 0.38 for positive stool cultures.
COMMENT
Overall, these results indicate that fecal blood testing, by either FIT or gFOBT, is inadequate as a guide to endoscopy in patients with iron deficiency anemia. In my opinion, FIT could still be used to provide reassurance (if negative) in a very elderly patient or one with multiple comorbidities who is at significant risk for colonoscopy complications. UC data have less relevance since the current trend is to utilize fecal calprotectin.
Note to readers: At the time we reviewed this paper, its publisher noted that it was not in final form and that subsequent changes might be made.
Douglas K. Rex, MD, FASGE
CITATION(S)
Lee MW, Pourmorady JS, Laine L. Use of fecal occult blood testing as a diagnostic tool for clinical indications: a systematic review and meta-analysis. Am J Gastroenterol 2020 Jan 10. (Epub ahead of print) (https://doi.org/10.14309/ajg.0000000000000495)
