Comparison of guaiac-based and immunochemical fecal occult blood tests for colorectal cancer screening in an Alaska Native population with high prevalence of Helicobacter pylori infection

INTRODUCTION: Alaska Native (AN) colorectal cancer (CRC) incidence and mortality rates are the highest of any ethnic/racial group in the United States. CRC screening guaiac-based fecal occult blood tests (gFOBT) are not currently recommended for AN people because of false positive results due to a high prevalence of Helicobacter pylori-associated hemorrhagic gastritis. This study evaluated whether the newer immunochemical FOBT (iFOBT) resulted in a lower false positive rate and higher specificity for detecting advanced colorectal neoplasia than gFOBT in a population with elevated prevalence of H. pylori infection.

METHODS: Population-based sample of asymptomatic AN adults (116 men, 188 women) ≥40 years old undergoing screening or surveillance colonoscopy (April 2008 - January 2012).

RESULTS: Specificity differed significantly (p < .0001) between gFOBT (76%; 95% CI = 71% to 81%) and iFOBT (92%; 95% CI = 89% to 96%). Among H. pylori positive participants (54%), specificity of iFOBT was even higher (93%; 95% CI = 89% to 97% vs. 69%; 95% CI = 62% to 77%). Overall, sensitivity did not differ significantly (p = 0.73) between gFOBT (29%; 95% CI = 12% to 45%) and iFOBT (36%; 95% CI = 18% to 53%). PPV was 11% for gFOBT and 32% for  iFOBT.

CONCLUSIONS: The iFOBT had a significantly higher specificity than gFOBT, especially in participants with current H. pylori infection. The iFOBT represents a potential strategy for expanding CRC screening among Alaska Native and other populations with elevated prevalence of H. pylori, especially where access to screening endoscopy is limited.