Bowel Cancer Screening Test Significantly Less Accurate In Summer

Main Category: Colorectal Cancer
Also Included In: Cancer / Oncology
Article Date: 06 Jul 2010 - 3:00 PDT

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The bowel cancer screening test is significantly less likely to pick up cancerous changes in summer than it is in winter, shows research published online in the journal Gut.

This could have significant implications for the risk of interval cancers - malignancies that develop between screenings - say the authors, who point out that this is the first research to highlight the impact of temperature on the screening test's accuracy.

Bowel cancer screening relies on the detection of blood hidden in a stool sample - a procedure referred to as the faecal occult blood test, or FOBT for short. The older type of test, known as the gFOBT, is gradually being replaced by the newer iFOBT, which is more sensitive and better at picking up cancer and its precursor - adenoma.

The authors analysed the impact of ambient temperature on the performance of iFOBTs in the Italian national screening programme in Florence over several different seasons.

Their analysis included temperature variations between faecal sampling and the return of the test sample, which averaged around 7 days, as well as the time in the laboratory refrigerator, which averaged around 4 days.

In all, just under 200,000 FOBT results were assessed for haemoglobin (Hb) levels - the protein in blood which colours it red.

They found that Hb levels were significantly lower in the summer months. Average levels were 27.6 in spring; 25.2 in summer; 29.2 in autumn; and 29.5 in winter.

Statistical analysis indicated that the FOBT was 17% less likely to test positive for signs of bowel cancer in the summer than it was in the winter. Every one degree rise in temperature reduced the likelihood of a positive test result by 0.7%.

And in the summer, the likelihood of the test picking up a cancer or an advanced adenoma was around 13% lower than it was in the winter.

"During the summer, significant neoplasia [cancerous changes] will be missed, which will increase the number of interval cancers," warn the authors. And they conclude: "Our observations have important implications for the organisation of iFOBT based screening programmes. [These] are greatest for those countries with wide seasonally related temperature variations."

Influence of seasonal variations in ambient temperatures on performance of immunochemical faecal occult blood test for colorectal cancer screening: observational study from the Florence district Gut Online First 2010; doi 10.1136/gut.2009.200873

Source:
British Medical Journal

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