[Diagnostic validity of fecal occult blood test in infants with food protein-induced allergic proctocolitis].

Introduction: Food protein-induced allergic proctocolitis (FPIAP) is the most frequent presenta tion of non-IgE mediated food allergy (FA). The diagnosis is made by oral food challenge, however, non-invasive diagnostic tests are not available. In Chile, the fecal occult blood test (FOBT) is fre quently used to confirm FPIAP, however, there are no studies that support this practice.

Objective: To establish the diagnostic validity of FOBT in the evaluation of infants with FPIAP.

Patients And Method: Case-control study with prospective recruitment of infants with rectal bleeding and suspicion of FPIAP, and controls were healthy infants, in whom the FOBT was conducted. All cases underwent an elimination diet, after which the diagnosis of FPIAP was confirmed by oral food cha llenge.

Results: 25 cases and 29 controls were included without significant differences in age, gen der, type of delivery, feeding, and maternal age. The cases had higher rates of allergic comorbidities, medication use, and family history of allergy. The FOBT was positive in 84% of cases and in 34% of controls (p < 0.001). The sensitivity of the FOBT for the diagnosis of FPIAP was 84%, specificity was 66%, positive predictive value 68%, and the negative predictive value 83%. The area under the ROC curve was 0.75 (CI 95% 0.61-0.88).

Conclusions: Although the FOBT has an adequate sensitivity to diagnose FPIAP in infants with rectal bleeding, this test had abnormal results in more than a third of healthy infants. Therefore, the routine use of FOBT is not recommended for the diagnosis of FPIAP.