Colorectal cancer is a major cause of cancer-related morbidity and mortality worldwide, and early detection significantly improves patient outcomes. The fecal immunochemical test (FIT) is a non-invasive stool-based test used for detection of colorectal cancer; however, its diagnostic performance varies according to lesion type and anatomical location.

This prospective observational cohort study aims to evaluate the diagnostic accuracy of quantitative fecal immunochemical testing (qFIT) in detecting colorectal cancer and precancerous lesions, including advanced adenomas and sessile serrated lesions, in adults undergoing colonoscopy in Sohag Government. The study will assess the sensitivity, specificity, and optimal cutoff values of qFIT according to lesion type, location, and histopathological characteristics.

This is a prospective observational cohort study conducted at a tertiary care endoscopy unit in Sohag Government. Adult patients aged 40 to 75 years who are referred for diagnostic or screening colonoscopy will be invited to participate.

All eligible participants will provide a stool sample for quantitative fecal immunochemical testing (qFIT) prior to bowel preparation. Fecal hemoglobin concentration will be measured using a quantitative FIT assay and expressed as micrograms of hemoglobin per gram of stool.

All participants will subsequently undergo colonoscopy as part of routine clinical care. Colonoscopic findings will be recorded, including lesion presence, anatomical location (proximal colon, distal colon, or rectum), size, and morphology. Biopsy or polypectomy specimens will be examined histopathologically to confirm colorectal cancer, advanced adenomas, or sessile serrated lesions.

The diagnostic performance of qFIT will be evaluated by calculating sensitivity, specificity, positive predictive value, and negative predictive value for detection of colorectal cancer and precancerous lesions. Receiver operating characteristic (ROC) curve analysis will be used to determine optimal qFIT cutoff values according to lesion type and anatomical location. Associations between qFIT levels and lesion characteristics will also be analyzed.

Inclusion Criteria:

• Adults aged 40 to 75 years
• Individuals undergoing screening or diagnostic colonoscopy
• Participants able to provide informed consent

Exclusion Criteria:

• Age below 40 years or above 75 years
• History of colorectal surgery
• Inflammatory bowel disease
• Inadequate bowel preparation
• Refusal to participate

Adult participants undergoing screening or diagnostic colonoscopy at Sohag University Hospital, including individuals with colorectal cancer, precancerous lesions, or normal colonoscopy findings.

Individual participant data will not be shared. The data are collected and analyzed for an academic thesis and will be reported in aggregate form only, with no plan for public or external data sharing.