Predictive values of an immunological fecal occult blood test for the diagnosis of colorectal cancer compared using colonoscopy in symptomatic patients in Yaounde (Cameroon)

Abstract

Introduction The predictive value of immunological fecal occult blood (iFOB) testing for the screening of colorectal cancer has been well described in the Western world. However, its relevance in Sub-Saharan Africa (SSA) is not well evaluated. It could be altered by the other causes of lower gastrointestinal bleeding such as parasitic infections. The aim of this study was to highlight the performance of an iFOB test for the prediction of colorectal cancer (CRC) during colonoscopy in SSA. 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 with an indication for colonoscopy without any overt gastrointestinal bleeding were included. Sociodemographic and clinical data were collected. All consenting patients underwent a qualitative immunologic occult test through the iFOB test before colonoscopy. Data were analyzed using SPSS version 23.0 software. The performance of the iFOB test for the diagnosis of CRC during colonoscopy was evaluated in terms of sensitivity (Se), specificity (Sp), positive predictive value (PPV) and negative predictive value (NPV). Results We included 103 patients during the study period with a male predominance and a sex ratio of 1.7. The median age [IQR] was 52 [38—65] years (range 1 – 84 years). The most common colonoscopic 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% (95%CI: 56.7—96.2); the Sp was 63.9% (95% CI: 53—74); the PPV was 31.1% (95% CI: 24—39) and the NPV was 94.8% (95% 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.