Abstract
Screening for colorectal cancer using guaiac-based fecal occult blood tests (gFOBT) is well established in Western populations, but is hampered by poor patient compliance due to the imposed dietary restrictions. Fecal immunochemical tests (FIT) do not require dietary restriction, but are more expensive than gFOBT and therefore restrict its use in developing countries in Asia. However, Asian diets being low in meat content may not require diet restriction for gFOBT to achieve equivalent results. The objective of this study was to evaluate and compare the validity and suitability of gFOBT and FIT or a combination of the two in screening for colorectal neoplasias without prior dietary restriction in an Asian population. Patients referred to the Endoscopic Unit for colonoscopy were recruited for the study. Stool samples were collected prior to bowel preparation, and tested for occult blood with both gFOBT and FIT. Dietary restriction was not imposed. To assess the validity of either tests or in combination to detect a neoplasm or cancer in the colon, their false positive rates, their sensitivity (true positive rate) and the specificity (true negative rate) were analyzed and compared. One hundred and three patients were analysed. The sensitivity for picking up any neoplasia was 53% for FIT, 40% for gFOBT and 23.3% for the combination. The sensitivities for picking up only carcinoma were 77.8% , 66.7% and 55.5%, respectively. The specificity for excluding any neoplasia was 91.7% for FIT, 74% for gFOBT and 94.5% for a combination, whereas for excluding only carcinomas they were 84%, 73.4% and 93.6%. Of the 69 with normal colonoscopic findings, FOBT was positive in 4.3%, 23.2 %and 2.9% for FIT, gFOBT, or combination of tests respectively. FIT is the recommended method if we are to dispense with dietary restriction in our patients because of its relatively low-false positivity and better sensitivity and specificity rates.
Highlights
There is a reducing trend in the incidence of colorectal cancer (CRC) in the West (Greenlee et al, 2001) but in Malaysia CRC still forms 13.2% of all cancers and is the commonest cancer in males
We set out to compare the validity of Fecal immunochemical tests (FIT), guaiac-based fecal occult blood tests (gFOBT) or a combination of the two for detecting neoplasms of the colon and in patients in whom dietary restrictions were dispensed with
We decided to explore the option of non-dietary restriction in our study because we felt that it may improve participation
Summary
There is a reducing trend in the incidence of colorectal cancer (CRC) in the West (Greenlee et al, 2001) but in Malaysia CRC still forms 13.2% of all cancers and is the commonest cancer in males. Because FIT does not react with non-human globin, dietary restriction is not necessary when screening with these tests. While gFOBT is well-tested, cheaper and more appropriate for Malaysia as a screening test because of the large numbers involved, its need for dietary requirements is a problem. The purpose of the present study was to compare and evaluate the validity and suitability of these two screening tests in our population in whom dietary restriction was dispensed with. A test was considered positive if any blue color appeared in the test slide window within 20 to 120 seconds after the addition of developer. The test is considered positive if blue lines appeared at the lower and the upper centers of the strip. The appearance of single blue line (control line) at the upper end of the strip is considered a negative result. Patients with diverticula or hyperplastic polyps were classified as normal
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