Sputum eosinophil counts

[chknowle]

Our new pulmonologist has asked that we start performing quantitatvie sputum eosinophil counts.  I am having difficulty finding references to put together a written procedure. One article she shared suggested performing a 400 cell diff to report % eosinophils (ug!).  Anyone else performing them, and if you are performing quantitative measurements, how many cells do you count? Also, do you filter the sample through mesh gauze before preparing the smear?

 

[Auntie-D]

Totally pointless exercise as it depends on the quality of the sample. The vast majority of sputum samples are not 'deep coughs' so the count will be diluted down by saliva. Also with eosinophils being held by the mucus you are not going to get uniform counts with each sample of the sample you count. Using a weak acid and an agitator could homogenise the sample reducing this but surely present/absent will suffice? It seems like a terribly outdated idea when there are immunological ways of quantitatively monitoring disease process...

[chknowle]

Are you aware of any other specific tests that can be used to diagnose nonasthmatic eosinophilic bronchitis? This is what the physician is wanting to use the eosinophil count for. I have spent alot of time doing literature reviews and have not found an alternate test(s) to recommend to her. Any help would be appreciated.

[Auntie-D]

But they will also be there in the presence of asthma so not really diagnostic. Surely the presence/absence is enough.

The only time a count may be more reliable could be with broncholavages but then you would still need to lyse the mucus to get a reliable homogenised population. Plus a 'better' sample would yield more than a poor samples.

If that is what they insist on though maybe a % count would be better - a normal blood level would be <0.5%? Is the ratio the same in mucus?

[Auntie-D]

Thinking further, a better indication is biopsy- asthma has smooth muscle infiltration and IL-13 expression and NAEB is epithlial...

As the treatment for both is identical and both have a similar trigger, is there any diagnostic value in determining which is the cause other than for personal knowledge for the medic?