Delayed sample arrival at the laboratory does not lead to more false negatives in the Danish population screening for colorectal cancer

AbstractIn Denmark, biennial population screening for colorectal cancer was introduced in 2014 for all aged 50–74 years. Five laboratories representative for the regional division of Denmark perform the immunochemical testing of faecal occult blood in the screening samples (iFOBT, OC-Sensor (Eiken Chemical, cut-off 100 µg/L)). In July 2016, a new agreement on the public post-delivery entailed an increased lag time (five days) from the screening participant drops the screening sample into a mail-box until sample arrival at the laboratories. Previous work had reported that a lag time above five days led to more false negative iFOBT tests. We investigated if this was true also under Danish conditions. We performed two stability tests; one with sample storage at 30 °C for 14 days (N = 60), and another with sample storage at room temperature for 13 days (N = 10). We extracted data from our laboratory information system (LABKA) on all iFOBT tests performed in the entire Central Denmark Region (N = 104,328 patie...