Accuracy of biochemical markers for predicting nasogastric tube placement in adults--a systematic review of diagnostic studies.

OBJECTIVE: The objective of this study was to investigate the diagnostic performance of biochemical tests used to determine placement of nasogastric (NG) tubes after insertion in adults. DESIGN: A systematic review of diagnostic studies was undertaken. DATA SOURCES: A literature search of the bibliographic databases and the World Wide Web was performed to locate original diagnostic studies in English or Chinese on biochemical markers for detecting NG tube location. REVIEW METHODS: Studies in which one or more different tests were evaluated with a reference standard, and diagnostic values were reported or could be calculated were included. Two reviewers independently checked all abstracts and full text studies for inclusion criteria. Included studies were assessed for their quality using the QUADAS tool. Study features and diagnostic values were extracted from the included studies. RESULTS: Of the 10 studies included in this review, seven investigated the diagnostic accuracy of pH, one investigated the diagnostic accuracy of pH and bilirubin respectively, two a combination of pH and bilirubin and one a combination of pH, pepsin and trypsin levels in identifying NG tube location. All studies used X-rays as the reference standard for comparison. Pooled results demonstrated that a pH of

Methods for determining the correct nasogastric tube placement after insertion: a meta-analysis.

BACKGROUND: Nasogastric tubes are frequently used in the clinical setting for the management of patients who require decompression of the gastrointestinal tract, diagnosis and assessment, nutritional support and medication administration. A variety of bedside methods have been used either individually or in combination to assess NG tube placement. OBJECTIVES: The objective of this review is to present the best available evidence to support decisions pertaining to methods for determining the correct nasogastric tube placement after insertion. SEARCH STRATEGY: A literature search was performed using the following databases MEDLINE (1950 to Sept 2008), CINAHL (1982 to Sept 2008), EMBASE (1980 to Sept 2008) and All EBM Reviews (up to 3rd Quarter 2008). Chinese databases searched included WanFang Data (1998 to Sept 2008), China Journal Net (1994 to Sept 2008), Chinese Medical Current Contents (1994 to Sept 2008), Index to Chinese Periodical Literature (1970 to Sept 2008), and the Chinese Biomedical Literature Database (1980 to Sept 2008). In addition the reference lists of relevant trials and conference proceedings were also scrutinised. Investigators were contacted to elicit further information. SELECTION CRITERIA: Clinical trials, prospective studies, observational studies, case reports, and evaluation studies assessing the diagnostic accuracy of methods for determining the correct placement of nasogastric tube after insertion were considered for inclusion in the meta-analysis. DATA COLLECTION AND ANALYSIS: Eligibility of the trials for inclusion in the review, details of eligible trials and the methodological quality of the trials were assessed independently by two reviewers. Since not all trials reported true positive, true negative, false positive and false negative rates, these rates were calculated based on the data in the published papers. The two by two tables were reconstructed for each study, and sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio and negative likelihood ratio were calculated for each study. Diagnostic studies presenting insufficient data for construction of a two by two table were excluded from statistical analysis, but were included in the narrative part of the review. MAIN RESULTS: Twenty-six trials were included in this meta-analysis: three trials investigated the effectiveness of colorimetric capnometry in detecting inadvertent airway intubation; three trials reported the use of capnography to verify tube placement in airway and to differentiate between respiratory and GI tube placement; one trial compared the use of a portable capnograph with a disposable colorimetric CO2 indicator in detecting inadvertent respiratory intubation. There were nine trials made use of a variety of cut-off points based on the biochemical measurement parameters of feeding tube aspirates (pH, bilirubin, pepsin and trypsin) in differentiating gastric from respiratory and intestinal placement of feeding tubes; one trial evaluated the accuracy of six pH test-strips. There were nine trials investigated the effectiveness of using various methods to differentiate between respiratory and GI feeding tube placement which included the use of: spring gauge pressure manometer, magnetic detection, sonography, auscultation and visual inspection of aspirates. AUTHORS' CONCLUSION: The limited evidence obtained from the meta-analysis does not provide a substantial base for the development of practice guidelines. However, based on the trials undertaken to date, there is strong evidence to support the use of capnography or colorimetric capnometry for identification of feeding tube placement in mechanically ventilated patients. Until stronger evidence becomes available practice related to the diagnostic tests used within the clinical setting will continue to be dictated by local preferences and cost factors.