Evaluating the efficacy of fecal immunochemical test, fecal calprotectin, and serum C-reactive protein in diagnosing patients with chronic lower gastrointestinal symptoms.

Abstract

Accurate early detection of ileocolonic lesions in chronic lower gastrointestinal symptoms (LGIS) patients is often difficult due to the rarity of early-stage alarm signs. This study assesses the effectiveness of noninvasive blood and stool biomarkers in diagnosing ileocolonic lesions in patients with chronic LGIS undergoing colonoscopy. We conducted a prospective study between December 2019 and July 2022 involving patients with LGIS lasting a month or more. Prior to colonoscopy, we gathered clinical data, blood samples for C-reactive protein (CRP), and stool samples for fecal immunochemical test (FIT) and fecal calprotectin (FC) analysis. Out of 922 participants analyzed (average age 62, 37% male), 130 (14.1%) had significant colonoscopy findings, including cancer, advanced adenoma, and inflammatory conditions. Test effectiveness showed an area under the curve (AUC) of 0.630 for alarm features, CRP at 0.643, FIT at 0.781, and FC at 0.667. Combining stool tests with alarm features improved diagnostic precision. Those without alarm features had a high negative predictive value of 0.97 with low threshold FIT and FC, missing minimal significant lesions and no cancer. For patients with alarm features, dual high-cutoff test positivity showed a positive predictive value of 0.67. Adding CRP to fecal tests did not enhance accuracy. FIT and FC are valuable in evaluating LGIS. Negative results at low cutoffs can delay colonoscopy in limited resource settings, while positive results at dual high cutoffs substantiate the need for the procedure.