Observing a very frothy white layer on a bronchoalveolar fluid obtained with a very good yield (155/200ml) prompted me to measure both the albumin and protein content of this fluid. The beer-like appearance reminded me of dissolving human albumin some years backi in a lab experiment. The concentrations obtained were very low (measured with the technique used for detection of microproteinuria...).
Protein 0.132 g/L and albumin 11.2mg/L. So far I have not found reference values for these findings.
Anyone aware of the normal range of protein and albumin content in BAL fluid?
Is the froth related to the yield rather than to an increased protein content?
I would be sceptic to any provided reference values, as they would be highly dependent on how much you install, your yield, where you wedge the scope (how distal), your method of suctioning, what kind of lavage fluid you use, et cetera.
To my knowledge, there are no established reference values for BALF albumin or protein concentrations. The issue is that the concentration is altered by the amount of lavage solution instilled and the recovery obtained.
I agree with both comments. However, there is at least a widespread "standard" that 200ml (4x50ml) are instilled. Naturally the yield is variable and depends on many factors among others if the segement you are sampling is above or below of the tip of the bronchoscope (in the one case graviational forces help increase the yield), but admittedly there are a number of variations to the technique which will influene both the yield, the amount of air obtained during sampling, etc. I was just wondering if there are some reference values out there or some anecdotal reports on measurements of protein or albumin in BALF.
For the time being all I know is that in this non-pulmonary alveolar proteinosis case the magnitude of protein and albumin in BALF requires am assay that has a detection level similar to that required to detect microproteinuria.
Did not find the urea method in the literature (comment above), but maybe it relates to the method needed to detect very low levels of albumin for example in urine samples...?
The frothy aspect may be proportional to the surfactant concentration, i.e. a high surfactant content would likely be more frothy. Younger lungs may have higher content, older lungs and those from COPD patients would likely have less surfactant. Any thoughts on this aspect? Is it the high content of surfactant or the high protein or albumin level that makes BALF samples frothy?
Finally, did you get any information about it? I am interested in knowing if there are reference values in BALF proteins.
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