Obtain plastic collection cans from MLabs; all other containers, including paint cans, are unacceptable. Collect stool for a duration of 24, 48, or 72 hours (48 - 72 hour collection preferred); freeze and send entire collection. Continue collection until a minimum of 5 grams of stool are collected. Note collection duration, start date and time and end date and time on requisition. It is essential that laxatives, particularly mineral oil or castor oil, are not used during the collection period. Barium interferes with the assay. Synthetic fat substitutes such as Olestra interfere with the assay.