Taking medications to lower stomach acid may affect colorectal cancer screening test results

The immunological fecal occult blood test (IFBT) is a non-invasive test that detects the presence of non-visible blood in the stool to locate polyps in the colon that could develop into a malignant tumor in time. However, it is not a perfect test and can give a false positive result (a positive TSOFi followed by a colonoscopy without risk lesions or colorectal cancer), which can lead to distress and unnecessary colonoscopies, with their possible risks and additional costs for the public health system and the patient.

A new study has shown that the use of proton pump inhibitors (PPIs), a class of drugs used to block stomach acid production known as “prazols”, at the time of TSOFi increases the probability of obtaining a false-positive result by 13%.

Other medications such as non-steroidal anti-inflammatory drugs, acetylsalicylic acid, antibiotics and laxatives are also associated with a false test result. The effect of PPIs is independent of the consumption of other drugs. However, taking PPIs in combination with anti-inflammatory drugs greatly increases the likelihood of a false positive test result.

The recommendation to avoid the use of PPIs before having a FSCT could reduce the number of colonoscopies in the screening program by up to 3%. Before this recommendation could be made, however, prospective clinical studies would need to confirm these results.
https://pubmed.ncbi.nlm.nih.gov/33159805/