Corwin and Irwin developed an index for aspiration pneumonia based on the number of lipid-laden alveolar macrophages identified in a bronchoalveolar lavage. This can help diagnose or exclude aspiration pneumonia in a patient with lung disease. The authors are from the University of Massachusetts in Worcester.
Method:
(1) Fluid from a bronchoalveolar lavage is processed with smears prepared for cytology.
(2) The slides are stained for lipid using the oil red O stain.
(3) 100 alveolar macrophages are graded using the following scheme.
Amount of Lipid in the Alveolar Macrophage
Grade
none
0
one or few intracellular droplets
1
many distinct intracellular droplets
2
many confluent intracellular droplets with the nucleus still visible
3
many confluent intracellular droplets with the nucleus obscured
4
index =
= ((number of macrophages not staining) * 0) + ((number of macrophages staining as Grade 1) * 1) + ((number of macrophages staining as Grade 2) * 2) + ((number of macrophages staining as Grade 3) * 3) + ((number of macrophages staining as Grade 4) * 4)
The reported value for the index is the average of two determinations performed independently.
Interpretation:
• minimum index: 0
• maximum index: 400
• A cutoff >= 100 had a sensitivity of 100% and specificity of 57%. The negative predictive value was 100%.
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