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13-03-2013 | Infectious disease | Article

Amylase in bronchoalveolar lavage fluid predicts pneumonia


Free abstract

medwireNews: Levels of alpha-amylase in bronchoalveolar lavage (BAL) fluid can be used to detect pulmonary aspiration and predict bacterial pneumonia in critically ill, intubated adults, US researchers report.

The marker may therefore be useful as an early screening tool and help guide antibiotic management, say Curtis Weiss (Northwestern University Feinberg School of Medicine, Chicago) and colleagues.

"Aspiration is a diagnostic dilemma," Weiss and team explain in Critical Care Medicine. It is associated with a range of clinical manifestations and there is no routine test that can currently help with its detection.

"BAL amylase may be a convincing marker of aspiration, more comprehensive than previously investigated biomarkers," Weiss et al suggest. Since this protein is usually only found in the pancreas, salivary glands, and gastrointestinal tract, its presence in the lung is highly suggestive of aspiration.

The researchers conducted a retrospective study involving 280 adults being treated within five intensive care units at the same center. Adults were in need of mechanical ventilation, and testing of BAL fluid was performed within 72 hours of endotracheal intubation.

Results showed a strong association between BAL amylase levels and clinical risk factors for aspiration, including difficulty swallowing, altered consciousness, peri-intubation vomiting, difficult intubation, and cardiac arrest.

Indeed, while median levels of BAL amylase were 72 units/L in patients with no pre-intubation risk factors, they were 225 units/L and 492 units/L, respectively, for patients with one or two or more risk factors.

In addition, a concentration of BAL amylase of less than 125 units/L was associated with a significant 61% reduced risk for bacterial pneumonia, at an odds ratio of 0.39. BAL amylase had 70% sensitivity for detecting bacterial pneumonia, with a negative predictive value of 85%.

"Even though the amylase in BAL had a relatively long-lasting detection window, its dynamic changes should not be neglected," Chunxue Bai and colleagues (Zhongshan Hospital, Shanghai, China) comment in an editorial.

While the study findings are promising, they suggest that further confirmation and assessment of BAL amylase at more than one time point is needed.

The commentators also note that BAL is an invasive procedure that may not be practical to perform in all intensive care patients; the procedure would also require standardization.

Despite these caveats, Bai et al conclude: "The results from this study may guide the clinical management of aspiration."

By Sara Freeman, medwireNews reporter

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