Dietary interference with the use of Bilitec to assess bile reflux

The Bilitec probe, which uses bilirubin as a marker for the detection of du odeno-oesophageal reflux, is subject to interference from strongly coloured foods, which can cause erroneously high bilirubin absorbance readings. To overcome this problem it is necessary to ingest a diet that is free from su ch substances, We tested the bilirubin absorbance of 32 different food subs tances in an in vitro environment, including many of the foods that are cur rently recommended for consumption during Bilitec studies,'Dry' foods were blended with water, 'non-dry' solid foods were blended undiluted, and break fast cereals were blended with milk, Blended mixtures were then tested for bilirubin absorption either undiluted or after mixing with hydrochloric aci d. The 'absorbance' of weakly coloured foods was usually less than the commonl y accepted threshold of 0.14, and the 'absorbance' of strongly coloured foo ds was usually above this. The 'absorbance' of three substances was higher in an acid environment. Three of the currently recommended foods had a suff iciently high 'absorbance' to interfere with readings in the clinical situa tion. Of the 32 substances tested, only 13 are suitable when the 'absorbanc e' threshold is set at 0.14. This number can be increased to 19 if the thre shold is increased to 0.20, From the foods evaluated, enough are suitable at the 0.14 threshold to enab le a suitable diet to be constructed for most patients. Furthermore, many p otentially acceptable foods remain untested. Clarification of appropriate f ood substances will help patients to be an are which foods are safe to eat, so that food interference can be prevented during Bilitec studies.