High Rate of Positive Fecal Occult Blood Test in Healthy Infants: A Nested Case-control Study

Area of Science:

• Pediatric Gastroenterology
• Allergy Immunology
• Diagnostic Testing

Background:

• The guaiac fecal occult blood test (gFOBT) is commonly used to assess for food protein-induced allergic proctocolitis (FPIAP) in infants.
• Validation and positivity rates of gFOBT in early infancy for FPIAP diagnosis are not well-established.

Purpose of the Study:

• To evaluate the gFOBT positivity rate in healthy asymptomatic infants compared to infants diagnosed with FPIAP.
• To assess the reliability of gFOBT interpretation and compare results with quantitative fecal immunochemical test (FIT).

Main Methods:

• A nested case-control study analyzed frozen stool samples from infants aged two days to five months.
• Guaiac fecal occult blood test (gFOBT) was performed and interpreted by three blinded staff members.
• Quantitative fecal immunochemical test (FIT) for hemoglobin was used for comparison.

Main Results:

• Eight percent of healthy infants (up to 11% including equivocal results) tested gFOBT positive.
• Seventy-four percent of infants diagnosed with FPIAP tested gFOBT positive.
• Interrater reliability for gFOBT interpretation was 81%; 50% of positive healthy samples and 29% of positive FPIAP samples were also FIT positive.

Conclusions:

• Guaiac fecal occult blood test (gFOBT) positivity occurs in up to 11% of healthy infants.
• Interpretation of gFOBT results in young infants requires caution in diagnostic settings.
• Further research may be needed to establish definitive diagnostic criteria for FPIAP using gFOBT.