January 28, 2019
1 min read

Anticoagulants, aspirin increase risk for FIT false positives

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Fecal immunochemical tests have lower positive predictive value of colorectal cancer among patients who are regular users of aspirin and direct-acting oral anticoagulants, according to research published in Gastroenterology.

Kristen Ranheim Randel, MD, of the Cancer Registry of Norway, and colleagues wrote that anticoagulant medication — which is associated with gastrointestinal bleeding — are increasingly used among patients 50 years and older, the target population for CRC screening.

“Theoretically, antiplatelet drugs and anticoagulants may affect the efficacy of FIT screening in opposite directions,” they wrote. “The drugs may increase physiological blood loss from the colonic mucosa and facilitate bleeding from non-advanced lesions, thus decreasing FIT [positive predictive value (PPV)] for CRC and advanced adenoma. However, they may also facilitate bleeding from advanced colorectal lesions, resulting in increased PPV.”

Researchers conducted a cross-sectional study in an ongoing CRC screening trial in Norway comprising 4,908 patients with a positive FIT result and a follow-up colonoscopy. They defined patients who used regular aspirin (n = 1,008), warfarin (n = 147) or direct-acting anticoagulants (DOAC; n = 212) as users and matched them to non-users based on age, sex, screening center and screening round. The primary outcomes of the trial were PPV for CRC and advanced adenoma.

Among aspiring users, the PPV for CRC was 3.8% compared with 6.4% for matched non-users (P = .006), while PPV for advanced adenoma was 27.2% compared with 32.6% in non-users (P = .011). Additionally, investigators found that PPV for CRC was 0.9% in DOAC users compared with 6.8% in non-users (P = .001), and the PPV for advanced adenoma was 20.5% compared with 32.4% in non-users (P = .002). They found no significant difference among warfarin users vs. non-users.

Randel and colleagues wrote that their findings could have consequences for how patients are handled during CRC screening programs.

“Screening participants who use these drugs should be informed of increased risk of false positive results,” they wrote. “Particular attention should be shown to users of DOACs.” – by Alex Young

Disclosures: Randel reports no relevant financial disclosures. Please see the full study for all other authors’ relevant financial disclosures.