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Accuracy of alpha amylase in diagnosing microaspiration in intubated critically-ill patients
Florent Dewavrin1, Farid Zerimech2, Alexandre Boyer3
1Intensive Care Unit, Valenciennes Hospital, avenue Desandrouin, Valenciennes, France.
Objectives:
Amylase concentration in respiratory secretions was reported to be a potentially useful marker for aspiration and pneumonia. The aim of this study was to determine accuracy of α-amylase in diagnosing microaspiration in critically ill patients.
Methods:
Retrospective analysis of prospectively collected data collected in a medical ICU. All patients requiring mechanical ventilation for at least 48 h, and included in a previous randomized controlled trial were eligible for this study, provided that at least one tracheal aspirate was available for α-amylase measurement. As part of the initial trial, pepsin was quantitatively measured in all tracheal aspirates during a 48-h period. All tracheal aspirates were frozen, allowing subsequent measurement of α-amylase for the purpose of the current study. Microaspiration was defined as the presence of at least one positive tracheal aspirate for pepsin (>200 ng.mL-1). Abundant microaspiration was defined as the presence of pepsin at significant level in >74% of tracheal aspirates.
Results:
Amylase was measured in 1055 tracheal aspirates, collected from 109 patients. Using mean α-amylase level per patient, accuracy of α-amylase in diagnosing microaspiration was moderate (area under the receiver operator curve 0.72±0.05 [95%CI 0.61-0.83], for an α-amylase value of 1685 UI.L-1). However, when α-amylase levels, coming from all samples, were taken into account, area under the receiver operator curve was 0.56±0.05 [0.53-0.60]. Mean α-amylase level, and percentage of tracheal aspirates positive for α-amylase were significantly higher in patients with microaspiration, and in patients with abundant microaspiration compared with those with no microaspiration; and similar in patients with microaspiration compared with those with abundant microaspiration. α-amylase and pepsin were significantly correlated (r2 = 0.305, p = 0.001).
Conclusion:
Accuracy of mean α-amylase in diagnosing microaspiration is moderate. Further, when all α-amylase levels were taken into account, α-amylase was inaccurate in diagnosing microaspiration, compared with pepsin.
Insights
Alpha-amylase concentration in respiratory secretions offers moderate accuracy for diagnosing microaspiration in critically ill patients. However, it proves inaccurate when all amylase levels are considered, unlike pepsin.
Area of Science:
- Critical Care Medicine
- Pulmonary Medicine
- Biomarker Discovery
Background:
- Microaspiration is a significant concern in critically ill patients requiring mechanical ventilation.
- Pepsin has been utilized as a marker for microaspiration, but its diagnostic utility has limitations.
Purpose of the Study:
- To evaluate the accuracy of alpha-amylase concentration in respiratory secretions for diagnosing microaspiration in critically ill patients.
- To compare the diagnostic performance of alpha-amylase with pepsin in detecting microaspiration.
Main Methods:
- Retrospective analysis of prospectively collected tracheal aspirate data from mechanically ventilated patients.
- Alpha-amylase levels were measured in tracheal aspirates, with microaspiration defined by pepsin presence.
- Diagnostic accuracy was assessed using receiver operating characteristic (ROC) curves.
Main Results:
- Mean alpha-amylase levels showed moderate accuracy (AUC 0.72) in diagnosing microaspiration.
- When all amylase levels were considered, diagnostic accuracy decreased significantly (AUC 0.56).
- Alpha-amylase and pepsin levels demonstrated a significant correlation (r² = 0.305, p = 0.001).
Conclusions:
- Mean alpha-amylase concentration provides moderate accuracy for diagnosing microaspiration.
- Overall alpha-amylase levels are inaccurate for microaspiration diagnosis compared to pepsin.
- Further research may explore combined biomarkers for improved diagnostic accuracy.
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