The Effect of the Variability in Fecal Immunochemical Test Sample Collection Technique on Clinical Performance

Erin L. Symonds, Callum G. Fraser, Dawn Bastin, Grace Berwald, Graeme P. Young

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


Background: Fecal immunochemical test (FIT) performance can be affected by post-collection variables. Collection technique might also affect fecal hemoglobin concentration (f-Hb). Variation in quantity of feces collected in samples returned in a colorectal cancer detection program, and the effects of under-sampling, were assessed.Methods: Collection devices obtained from patients undergoing FIT were assessed for the color (in five classes) of the feces in buffer, mass, and f-Hb. Associations between these were examined in an in vitro study on Hb-spiked feces. Variables possibly associated with under-sampling were investigated using multivariable logistic regression. The effect of low sample mass on clinical performance (false-negative results) was determined.Results: Of 6,898 samples collected by 3,449 individuals (46.9% male, median age: 65.3 years), the buffer was lightest in color in 362 (5.2%), and darkest in 420 (6.1%). Samples with the lightest color had a significantly lower f-Hb compared with all darker classes (P < 0.001). Mass was recorded for 650 devices: The lightest colored samples had significantly lower mass (P < 0.05). The correlation between mass and f-Hb was confirmed in vitro (r = 0.897, P < 0.001). Low mass was not associated with age, sex, or technical factors (P > 0.05). Under-sampling related to the lightest color was not associated with false-negative results for colorectal cancer and advanced adenoma, but was for all neoplasia and inflammatory bowel disease.Conclusions: Wide variation existed in the amount of feces collected. Under-sampling results in lower measured f-Hb and may increase false-negative results.Impact: Color of sample buffer could be used to identify inadequate sampling.
Original languageEnglish
Pages (from-to)175-181
Number of pages7
JournalCancer Epidemiol Biomarkers Prev
Issue number1
Publication statusPublished - 1 Jan 2021
Externally publishedYes


  • Fecal immunochemical test
  • fecal hemoglobin concentration
  • Clinical Performance


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