Gastric Lipase Enhanced Nasogastric Tube Study in Neonates

STUDY OBJECTIVES

Primary Objective:

• To determine the sensitivity of the chemical (tributyrin) impregnated pH test strip in comparison to the routine pH test strip to increase the sensitivity of detection of correct positioning of the nasogastric tube

Secondary objectives:

• To measure the number of nasogastric tube re-insertion attempts that could be avoided if the tributyrin impregnated pH test strip was used instead of the standard pH test strip
• To determine the number of chest radiographs which could be avoided if the tributyrin impregnated pH test strip was used instead of the standard pH test strip
• To carry out human factors assessment of perceived usability, trust and acceptance of the lipase-based pH test strip

STUDY DESIGN Prospective point of care diagnostic accuracy study

Primary outcome

• Sensitivity of proposed test in determining correct nasogastric (NG) tube position

Secondary outcomes

• Number of chest x rays performed
• Time to confirm tube placement
• Number of nasogastric tube attempts to get the correct pH
• Assessment of human factors - Perceived usability, trust and acceptance from professionals' perspective

Subject selection and setting

Participants will be recruited from Imperial College Healthcare NHS Trust from the neonatal units at both the Queen Charlotte's and Chelsea and St. Mary's hospital sites. Eligible participants will be identified by the clinical team and recruited by a member of the research team.

The vast majority of admitted infants will require nasogastric tube insertion as part of their clinical management such as preterm infants, sick term infants with hypoxic- ischaemic encephalopathy and meconium aspiration syndrome as well as admitted infants for hypoglycaemia and jaundice management.

Study method

The clinical trial will be a diagnostic accuracy study of two diagnostic tests and will be reported in accordance with the Standards for reporting diagnostic accuracy studies (STARD) guidelines. The index tests will be (i) the novel tributyrin impregnated pH test strip and (ii) standard pH test strip. The reference test used for comparison will be chest x-ray performed earlier or later but with the same nasogastric tube in situ; or where this is not required 'trial by use' (any chest x-rays undertaken would be decided and authorised by the participant's clinical team who are clearly separated from the research team. Undergoing a chest x-ray does not from part of screening for the study and is not a requirement of the study protocol).

Ingenza novel lipase/pH test strip

The test detects the organic acid released from tributyrin, a chemical ester impregnated onto pH paper by the action of human gastric lipase that is stable in gastric juice and resistant towards antacid medications, as well as unlikely to migrate. Ingenza have impregnated enteral pH indicator strips that are in current clinical use with emulsion formulations of tributyrin, protected by intellectual property as human gastric lipase substrates. Therefore, the novel test strips will provide a positive result in the presence of an acidic environment (pH less than or equal to 5.5) or gastric lipase.

Index testing

After the tube insertion, the carer will aspirate the tube to obtain a sample of gastric fluid. This will be done immediately following insertion or as part of daily position confirmation that is routinely performed prior to initiation of nasogastric feeding. The aspirate will be used by the healthcare professional, as part of routine care and the remaining sample passed to a member of the research team. The healthcare professional will test the aspirate routinely and make their decision based on the current standard pH strip test. The remaining sample will be used by the research nurse blinded to the standard test, to wet the gastric lipase enhanced pH test strip. The research nurse will then independently assess the results of the study test paper at two minutes. Digital photographs of both the routine and the study test papers will be assessed independently by member of the study team to verify the findings. The healthcare professional will be blinded to the results of the proposed test strip. The research nurse will record the results of the standard test strip only after documenting the result of the proposed test.

For standard pH strips a pH of ≤5.5 will indicate correct tube placement and >5.5 indicates incorrect nasogastric tube position. For the gastric lipase enhanced pH strip test a positive result will be determined according to the manufacturer's recommendations.

Inclusion criteria

All infants (preterm and term) who require the insertion of nasogastric tubes for supplementary enteral feeding as part of their routine clinical management

Exclusion criteria

Clinically unstable, critically ill infants Infants undergoing palliative care Infants with bowel conditions such as necrotising enterocolitis, bowel obstruction

Inclusion criteria

• All infants (preterm and term) who require the insertion of nasogastric tubes for supplementary enteral feeding as part of their routine clinical management

Exclusion criteria

• Clinically unstable, critically ill infants
• Infants undergoing palliative care
• Infants with bowel conditions such as necrotising enterocolitis, bowel obstruction