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. 2014 Mar 6;9(6):e90851.
doi: 10.1371/journal.pone.0090851. eCollection 2014.

Accuracy of alpha amylase in diagnosing microaspiration in intubated critically-ill patients

Florent Dewavrin  1 , Farid Zerimech  2 , Alexandre Boyer  3 , Patrice Maboudou  2 , Malika Balduyck  2 , Alain Duhamel  4 , Saad Nseir  5
Affiliations

Accuracy of alpha amylase in diagnosing microaspiration in intubated critically-ill patients

Florent Dewavrin et al. PLoS One. .

Abstract

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.

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Conflict of interest statement

Competing Interests: The authors have read the journal’s policy and have the following conflicts: SN: Covidien (lecture). Other authors: none. This does not alter the authors’ adherence to all the PLOS ONE policies on sharing data and materials.

Figures

Figure 1
Figure 1. Study flowchart.
Figure 2
Figure 2. Accuracy of mean α-amylase in diagnosing microaspiration.
Area under the receiver operator curve 0.72±0.05 [95% CI 0.61–0.83].
Figure 3
Figure 3. Accuracy of all α-amylase levels, coming from all tracheal aspirates, in diagnosing microaspiration.
Area under the receiver operator curve 0.56±0.05 [95% CI 0.53–0.60].
Figure 4
Figure 4. Mean α-amylase levels in patients with no microaspiration.
Figure 5
Figure 5. Mean α-amylase levels in patients with microaspiration.
Figure 6
Figure 6. Mean α-amylase levels in patients with abundant microaspiration.
Figure 7
Figure 7. Correlation between α-amylase and pepsin.
r2 =  O.305, P = 0.001.
See this image and copyright information in PMC

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