RT Journal Article
SR Electronic
T1 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
JF Gut
JO Gut
FD BMJ Publishing Group Ltd and British Society of Gastroenterology
SP 1511
OP 1515
DO 10.1136/gut.2009.200873
VO 59
IS 11
A1 Grazia Grazzini
A1 Leonardo Ventura
A1 Marco Zappa
A1 Stefano Ciatto
A1 Massimo Confortini
A1 Stefano Rapi
A1 Tiziana Rubeca
A1 Carmen Beatriz Visioli
A1 Stephen P Halloran
YR 2010
UL http://gut.bmj.com/content/59/11/1511.abstract
AB Background Faecal occult blood testing (FOBT) in population screening has proved to be effective in reducing mortality from colorectal cancer. In Italy a latex agglutination FOBT has been adopted for a single-sample screening programme. The aim of this study was to examine the performance of FOBTs in the Florence screening programme over several seasons to evaluate the impact of variations in ambient temperature on the performance of the screening test.Methods Measured haemoglobin (Hb) concentrations were aggregated into seasons with their average ambient temperature (AAT). Using logistic regression, the AAT over the period preceding the test measurement was analysed. This period included the time between faecal sampling and return of the test sample (mean 7 days) and the time in the laboratory refrigerator before analysis (mean 4 days). The AAT from days 5–11 before analysis of the test sample was considered a determinant of test positivity. The Kruskal–Wallis rank test was used to evaluate the significance of seasonal and/or AAT-related differences in Hb concentration. A logistic regression model adjusted for sex, age, season and screening episode (first or repeated examination) was constructed.Results 199 654 FOBT results were examined. Mean FOBT seasonal Hb concentrations (ng/ml) were: spring 27.6 (95% CI 26.2 to 29.1); summer 25.2 (95% CI 23.1 to 27.3); autumn 29.2 (95% CI 27.7 to 30.6); winter 29.5 (95% CI 27.9 to 31.1). Logistic regression showed that there was a 17% lower probability of the FOBT being positive in summer than in winter. The results of the logistic regression showed that an increase in temperature of 1°C produced a 0.7% reduction in probability of a FOBT being positive. In the summer the probability of detecting a cancer or an advanced adenoma was about 13% lower than in the winter.Conclusions This study showed that there is a significant fall in Hb concentration at higher ambient temperatures. These results will have important implications for the organisation of immunochemical FOBT-based screening programmes, particularly in countries with high ambient temperatures.