Fecal Immunohistochemistry Testing for Early Colorectal Cancer Diagnosis in South Africa

Name: Alexander (Sascha) Morris
School: Vagelos College of Physicians and Surgeons, Class of 2026

Name: Madhav Nekkar
School: Vagelos College of Physicians and Surgeons, Class of 2026; Varmus Global Scholar 2023

Mentors: Vasudevan Naidoo, MD; Shakeel Kader, MD; Yoanna Pumpalova, MD

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Abstract

Research Question: Can stool-based point-of-care fecal immunohistochemistry testing (FIT) triage symptomatic patients for colonoscopy and facilitate early diagnosis of colorectal cancer (CRC) in South African public hospitals? 

Background: CRC is the third most diagnosed cancer globally with a rising incidence across sub-Saharan Africa. In South Africa, advanced stage at diagnosis drives poor outcomes. Endoscopic capacity is limited and not equitably distributed, making early CRC diagnosis guidelines difficult to implement. Hence, validation of a more accessible and affordable diagnostic option is crucial. 

Methods: A prospective cohort study design was utilized. Adult patients (≥18 years old) with ≥1 “red flag” symptom (weight loss, change in bowel habits, rectal bleeding, iron deficiency/anemia, abdominal mass) referred for colonoscopy at two hospitals in Durban were invited to participate. Results from FIT tests and colonoscopy (polyps and malignant lesions) were recorded. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of FIT for polyp or CRC were calculated using R.  

Results: Of 72 patients (mean age 52±16.5 years, 44.4% female), 14 (19.4%) had positive colonoscopies (10 polyp and 4 malignant lesions), while 35 (48.6%) had positive FIT tests. FIT had 57% sensitivity, 53% specificity, 23% PPV and 84% NPV for colonic polyps or CRC. 

Conclusions: In symptomatic South African patients referred for colonoscopy, FIT has a moderate NPV for colonic polyps or CRC but a weak PPV. More data from patients who are actively being recruited to reach a goal of 300 in total may reveal stronger predictive value from this test.