Predictive Values of an Immunological Fecal Occult Blood Test for the Diagnosis of Colorectal Cancer at the Colonoscopy in Yaounde (Cameroon)

Abstract

Introduction: Colorectal cancer (CRC) is a public health problem in the world. The gold standard test for an early diagnostic is a colonoscopy with a histological exam of the lesion. This is invasive and expensive and few available in rural areas of sub-Saharan African (SSA) countries. The immunological fecal occult blood (iFOB) test have shown its predictive value for the screening of the CRC in west. But its interest in SSA is few studied. It could be altered by the other causes lower digestive bleeding such as worm digestive infections. The aim of this study was to highlight the performance of an iFOB test for the diagnosis of CRC regarding the colonoscopy in SSA area. Methodology: We conducted an analytical cross-sectional study in two digestive endoscopic centers of Yaoundé (Cameroon) from the 1st July to the 31 November 2022. Patients presenting an indication for colonoscopy without any visible digestive bleeding were included. We collected sociodemographic data and clinical signs. Then, these patients gave their consent and underwent a qualitative immunologic occult test through the iFOB test before the colonoscopy. Data were analyzed using SPSS version 23.0 software. The performance of the iFOB test for the diagnosis of CRC at colonoscopy was evaluated in terms of sensitivity (Se), specificity (Sp), positive predictive value (PPV) and negative predictive value (NPV). Results: We registered 103 patients during the period. They were predominantly male with a sex ratio of 1.7. The median age was 52 ± 13 years (range 1 – 84 years). The most common colonoscopy lesions were polyps in 23 patients (22.3%), CRC in 17 patients (16.5%) and hemorrhoids in 15 patients (14.6%). Patients testing positive for iFOB test accounted for 43.7% (45 patients). Among these patients, 31.1% (14 patients) had a CRC. The Se of the occult blood test for CRC detection was calculated to be 82.3% (CI: 56.7 - 96.2); the Sp was 63.9% (CI: 53 - 74); the PPV was 31.1% (CI: 24 - 39) and the NPV was 94.8% (CI: 86.6 - 98.1). Conclusion: the iFOB test has a good NPV, but a poor PPV for the diagnosis of CRC in our study.