Study to determine the likely accuracy of pH testing to confirm nasogastric tube placement

Rowat, A. M. , Graham, C. and Dennis, M. (2018) Study to determine the likely accuracy of pH testing to confirm nasogastric tube placement. BMJ Open Gastroenterology, 5, e000211. (doi: 10.1136/bmjgast-2018-000211) (PMID:29915668) (PMCID:PMC6001908)

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Abstract

Objective: To establish the likely accuracy of pH testing to identify gastric aspirates at different pH cut-offs to confirm nasogastric tube placement. Methods: This prospective observational study included a convenience sample of adult patients who had two (one fresh and one frozen) gastric and oesophageal samples taken during gastroscopy or two bronchial and saliva samples taken during bronchoscopy. The degree of observer agreement for the pH of fresh and frozen samples was indicted by kappa (k) statistics. The sensitivities and specificities at pH ≤5.5 and the area under the receiver operating characteristics (ROC) curve at different pH cut-offs were calculated to identify gastric and non-gastric aspirates. Results: Ninety-seven patients had a gastroscopy, 106 a bronchoscopy. There was complete agreement between observers in 57/92 (62%) of the paired fresh and frozen gastric samples (k=0.496, 95% CI 0.364 to 0.627). The sensitivity of a pH ≤5.5 to correctly identify gastric samples was 68% (95% CI 57 to 77) and the specificity was 79% (95% CI 74 to 84). The overall accuracy to correctly classify samples was between 76% and 77%, regardless of whether patients were taking antacids or not. The area under the ROC curve at different pH cut-offs was 0.74. Conclusion: The diagnostic accuracy of pH ≤5.5 to differentiate gastric from non-gastric samples was low, regardless of whether patients were taking antacids or not. Due to the limited accuracy of the pH sticks and the operators’ ability to differentiate colorimetric results, there is an urgent need to identify more accurate and safer methods to confirm correct placement of nasogastric tubes.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Rowat, Dr Anne
Authors: Rowat, A. M., Graham, C., and Dennis, M.
College/School:College of Medical Veterinary and Life Sciences > School of Medicine, Dentistry & Nursing > Nursing and Health Care
Journal Name:BMJ Open Gastroenterology
Publisher:BMJ Publishing Group
ISSN:2054-4774
ISSN (Online):2054-4774
Published Online:09 June 2018
Copyright Holders:Copyright © 2018 The Authors
First Published:First published in BMJ Open Gastroenterology 5(1): e000211
Publisher Policy:Reproduced under a Creative Commons License

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