MedWire News: Study results show that the immunochemical fecal occult blood test (iFOBT) for detecting colorectal cancer is approximately 13% less accurate in the summer than in the winter.
The iFOBT relies on accurate detection of hemoglobin (Hb) in a stool sample to predict neoplasia. The researchers say their result is due to the unstable nature of Hb in feces and the higher likelihood of denaturation of fecal Hb at higher temperatures.
In this study, Grazia Grazzini (Cancer Prevention and Research Institute, Florence, Italy) and colleagues analyzed 199,654 iFOBT results taken as part of the Florence regional colorectal cancer screening program.
When divided by season, the number of results taken in fall, summer, winter, and spring was 69,301, 25,360, 41,725, and 63,268, respectively. Average ambient temperatures in the respective seasons were 14.0, 25.1, 7.9, and 16.0 °C, respectively. The corresponding mean seasonal Hb concentrations were 29.2, 25.2, 29.5, and 27.6 ng/ml.
Following logistic regression analysis the team calculated that there was a 17% lower probability of an iFOBT being positive in summer than in winter. More specifically, an increase in ambient temperature of 1°C reduced the likelihood of an iFOBT being positive by 0.7%.
Overall, the researchers found that there was a 13% lower probability of detecting a cancer or an advanced adenoma with iFOBT in the summer than the winter.
Writing in the journal Gut, the investigators warn: "These results will have important implications for the organization of iFOBT-based screening programs, particularly in countries with high ambient temperatures."
They suggest: "The use of temperature tracking devices to gather these temperature profiles during the summer period should be considered by all programs.
"The observations described in this study need to be confirmed by other programs working under a variety of different climatic conditions."
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