Screening Performance Differences among Fecal Test Brands

The myriad of available fecal immunochemical tests (FITs) have typically been found to have dissimilar cutoff values as FIT units are frequently expressed as the hemoglobin concentration in sampling, nonexchangeable, bottle buffers.

Different brands of FITs with the same cutoff hemoglobin concentration have been reported to perform differently in detection of colorectal cancer (CRC).

The study, published in the December issue of Gastroenterology, was led by Tsung-Hele Chiang, MD, from the National Taiwan University in Taipei and his colleagues. They observed a group of 956,005 Taiwanese patients aged 50 to 69 years enrolled in a national CRC screening program designed to compare 2 different quantitative FITs. Based on a standardized reporting unit system, each test shared the same cutoff concentration for a positive finding: 20 μg hemoglobin/g feces. From 2004 to 2009, of the total subjects, 78% were tested with the OC-Sensor, while the remaining 22% were administered the HM-Jack.

According to the study, the OC=Sensor test and HM-Jack test detected CRC in 21% and 17% of the patients respectively. They noted a significant difference in test sensitivity: 80% v 68% along with the potential to detect “proximal CRC” and epitopes of degraded hemoglobin.

This revealed inherent differences between test results for the positive predicative value for cancer detection (1.29) as well as the rates of interval cancer (75%) following an adjustment for cofounders.

It was reported that any subject with a positive test was referred to one of nearly 485 hospitals to await confirmatory diagnosis by either a total colonoscopy or sigmoidoscopy plus barium enema.

Study results showed that different brands of quantitative FITS, indeed performed differently during mass screenings despite identical cutoff hemoglobin concentration. The authors wrote, “Population-level data should be gathered to verify the credibility of quantitative laboratory findings.”