The NIHR Diagnostic Evidence Co-operative (DEC) London and Scottish SME Ingenza are collaborating to assess and develop a novel enzyme-based test for the accurate positioning of nasogastric feeding tubes (NG tubes). Incorrect positioning of NG feeding tubes can lead to severe harm or death. This project aims to develop a more accurate test for determining the position of NG tubes for safe feeding.
Need for better diagnostic tests
At least 1 million NG tubes are used in the NHS each year and 1.5 billion worldwide. Currently the recommended method to check the correct positioning of NG tubes is through the use of pH paper. Feeding is considered safe if the pH reading is 5.5 or below. If the pH is above this value, the patient is sent for a chest x-ray. Feeding will only commence if the x-ray finds the tube safely situated in the stomach. There are several problems with this approach.
Using a pH cut off of 5.5 cannot rule out feeding into the oesophagus, placing patients at risk of reflux. In some cases pH misinterpretation can lead to erroneous lung placement of tubes.
pH paper can be less sensitive (increased false negatives) for patients taking antacid medications.
Chest x-rays are considered gold-standard but are subject to misinterpretations. Consequences of erroneous feeding decisions can be severe. Thirty-two deaths and eighty incidents of severe harm were reported to the NPSA between 2003 and 2010.
Our work with Ingenza
The new test, developed by Ingenza, detects human gastric lipase (HGL) which is stable in gastric juice, and resistant towards antacid medications. A pilot study showed that the test had perfect specicity and near-perfect sensitivity. This outcome, if validated, allows the test to potentially transform the existing patient care pathway in a number of ways:
Improved accuracy than gastric acid detection alone and therefore improved patient safety.
Low cost, easy to use and interpret and therefore can reduce human errors, with no change to current practice.
Joint funding application
The NIHR-DEC London and Ingenza were successful in a joint application for an Innovate UK Biotechnology Catalyst grant to refine the biochemistry of the test and to improve its design. This will be followed by a rigorous clinical trial, where evidence on test validity, cost-effectiveness, clinical utility and barriers for implementation will be generated. The project will allow evidence-based development and the eventual adoption of the innovative technology.
The new test has the potential to transform existing patient care to be safer and more efficient, and it is likely to become the new standard of care. The cost savings to the NHS will also be significant. We estimate that in the UK alone about 4 million pH-based diagnostic tests for NG feeding tube placement are currently at risk of being compromised (e.g. by the effects of antacid medications) per year. Each of these requires confirmatory X-ray costing, on average £120 each. The new test costs less than £1 each, and if only 20% of patients receiving antacids required X-ray confirmation, then the cost to medical providers in the UK would be more than £120 million per year. If just 25% of NG feeding tube placement X-rays could be avoided then the annual direct costs savings to UK healthcare providers in x-ray treatment alone could be in excess of £30 million per year.