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Open Access Research article

Double sampling of a faecal immunochemical test is not superior to single sampling for detection of colorectal neoplasia: a colonoscopy controlled prospective cohort study

Frank A Oort1*, Sietze T van Turenhout1*, Veerle MH Coupé2, René WM van der Hulst3, Eric IC Wesdorp4, Jochim S Terhaar sive Droste1, Ilhame Ben Larbi1, Shannon L Kanis1, Edwin van Hengel5, Anneke A Bouman5, Gerrit A Meijer6 and Chris JJ Mulder1

Author Affiliations

1 Gastroenterology and Hepatology, VU University Medical Centre, De Boelelaan 1118, Amsterdam, The Netherlands

2 Epidemiology and Biostatistics, VU University Medical Centre, De Boelelaan 1118, Amsterdam, The Netherlands

3 Gastroenterology and Hepatology, Kennemer Gasthuis, Boerhaavelaan 22, Haarlem, The Netherlands

4 Gastroenterology and Hepatology, Sint Lucas Andreas Hospital, Jan Tooropstraat 164, Amsterdam, The Netherlands

5 Clinical Chemistry, VU University Medical Centre, De Boelelaan 1118, Amsterdam, The Netherlands

6 Pathology, VU University Medical Centre, De Boelelaan 1118, Amsterdam, The Netherlands

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BMC Cancer 2011, 11:434  doi:10.1186/1471-2407-11-434

Published: 10 October 2011

Abstract

Background

A single sampled faecal immunochemical test (FIT) has moderate sensitivity for colorectal cancer and advanced adenomas. Repeated FIT sampling could improve test sensitivity. The aim of the present study is to determine whether any of three different strategies of double FIT sampling has a better combination of sensitivity and specificity than single FIT sampling.

Methods

Test performance of single FIT sampling in subjects scheduled for colonoscopy was compared to double FIT sampling intra-individually. Test positivity of double FIT sampling was evaluated in three different ways: 1) "one of two FITs+" when at least one out of two measurements exceeded the cut-off value, 2) "two of two FITs+" when both measurements exceeded the cut-off value, 3) "mean of two FITs+" when the geometric mean of two FITs exceeded the cut-off value. Receiver operator curves were calculated and sensitivity of single and the three strategies of double FIT sampling were compared at a fixed level of specificity.

Results

In 124 of 1096 subjects, screen relevant neoplasia (SRN) were found (i.e. early stage CRC or advanced adenomas). At any cut-off, "two of two FITs+" resulted in the lowest and "one of two FITs+" in the highest sensitivity for SRN (range 35-44% and 42%-54% respectively). ROC's of double FIT sampling were similar to single FIT sampling. At specificities of 85/90/95%, sensitivity of any double FIT sampling strategy did not differ significantly from single FIT (p-values 0.07-1).

Conclusion

At any cut off, "one of two FITs+" is the most sensitive double FIT sampling strategy. However, at a given specificity level, sensitivity of any double FIT sampling strategy for SRN is comparable to single FIT sampling at a different cut-off value. None of the double FIT strategies has a superior combination of sensitivity and specificity over single FIT.