Abstract

PINHO-COSTA, Luís de  and  SOUSA, Hélder. The influence of acetylsalicylic acid on faecal occult blood testing: an evidence-based review. Rev Port Med Geral Fam [online]. 2014, vol.30, n.4, pp.244-252. ISSN 2182-5173.

Introduction: Fecal occult blood test (FOBT) screening for colorectal cancer (CRC) is often performed with patients taking acetylsalicylic acid (ASA). There is doubt about the efficacy of CRC screening with ASA treatment. Objective: To review the evidence for the impact of prophylactic ASA consumption on the diagnostic accuracy of FOBT screening for CRC. Methods: In February 2013, a search for guidelines, meta-analysis, reviews and original articles was conducted on PubMed, EBM databases, Index RMP and in the references in eligible articles. The MeSH terms aspirin and occult blood and corresponding DeCS (Portuguese search terms) were used as keywords. Eligible publications compared the accuracy of FOBT screening for CRC with ASA versus screening without ASA. The STARD checklist and GATE framework were applied for critical appraisal. The Oxford EBMC Levels of Evidence (LE) were used. Results: Of the 698 articles obtained, three original studies matched eligibility criteria. One study examined the guaiac-FOBT (LE 4) and two other studies examined the immunological-FOBT (LE 2 and 4). The latter two studies showed no statistically significant difference in the Positive Predictive Value (PPV) of immunological-FOBT for CRC with or without ASA. One of the studies examined other performance measures and showed increased sensitivity for diagnosis of CRC but no improvement in global accuracy for the immunoassay with ASA treatment. The guaiac-FOBT results may have a reduced PPV but this finding was inconclusive. Conclusion: There is inconclusive evidence regarding the impact of ASA on the accuracy of the guaiac-FOBT. For the immunoassay, ASA consumption might have null or positive effect on its diagnostic accuracy.

Keywords : Aspirin; Occult Blood; Diagnostic Performance.

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