[Does prolonging the test period improve screening for colorectal cancer?].

Prolongation of Haemoccult-screening from 3 to 6 days in 3540 out-patients resulted in a rise of the positivity rate from 4.1 to 6.75%. This was accompanied by an increase of the detection rate by 10% in cancers and 25% in large adenomas. The predictive value of a positive test for colorectal neoplasia (carcinoma and large polyps together) dropped from 26.7 to 20.9%. More data are needed before general recommendation for change from the standard 3-day-test period can be given.