Development of a reliable and valid bedside test for bilirubin and its utility for improving prediction of feeding tube location

Background: The addition of laboratory bilirubin readings to an algorithm b ased on pH atone improves prediction of feeding tube location; although rel iable pH-teststrips are available, there is no bedside test to measure bili rubin in feeding tube aspirates. Objectives: This study was designed to test the efficacy of a bilirubin tes tstrip with a newly developed scale in measuring the bilirubin content in f eeding tube aspirates, and to determine the effectiveness of a combination of readings from pH and bilirubin teststrips in predicting feeding tube loc ation. Methods: A total of 631 gastrointestinal specimens for concurrent pH and bi lirubin testing were obtained from adult, acutely ill patients with newly i nserted feeding tubes (nasogastric, n = 328; nasointestinal, n = 303) withi n 5 minutes of radiographs taken to determine tube location, in addition, 2 25 respiratory specimens were tested. Bilirubin was measured with a teststr ip incorporating a newly developed colorimetric visual bilirubin (VBIL) sca le, and by a laboratory assay, pH was measured with a teststrip and a pH-me ter. Results from the bilirubin and pH tests were read by research assistan ts and staff nurses and compared with tube location as determined by radiog raphy. Results: The correlation between readings made from the 5-point VEIL scale and the trimmed laboratory bilirubin was 0.93, with dichotomized readings c orrelating 0.87 and kappa equal to 0.86. A pH greater than 5 and a bilirubi n less than 5 mg/dL successfully identified 100% of the 225 respiratory cas es. In the category of pH 5 or less and bilirubin less than 5 mg/dL, 98% of the cases were gastric cases. In the category of pH greater than 5 and bil irubin 5 or higher mg/dL, nearly 88% of the cases were intestinal cases. Conclusions: The newly developed VEIL scale is effective in determining the bilirubin content in feeding tube aspirates. Furthermore, compared with pr edicting tube location from pH-paper alone, dichotomized readings from the VEIL scale/bilirubin teststrip used in combination with a pH-teststrip impr oved the ability to differentiate between respiratory and gastrointestinal tube placement, as well as between gastric and intestinal tube placement. R efinement of the VEIL scale is indicated to increase its accuracy.