Different laboratories - different results of sputum investigations

Question

Dear expert team,
I have a question concerning germs in the sputum.
About one time a year there is an investigation of the sputum in the CF-center, where in the last years Pseudmonas (different types) have been detected each time, in the sputum as well as in the nasal secretions.
Furthermore, there are inbetween (about 3-4 times a year) investigations of the sputum performed at the pulmonologist locally (different microbiological lab than the CF-center). Here the Pseudomonas is detected very frequently (also different types of Pseudmonas) as well as other germs (e.g. sp. Stentrophomonas, not exactly describable gram-negative germs).
Once a year the general practitioner performs an investigation of the sputum (again a different laboratory). And here, until now, a Pseudomonas has never been detected (and no other germs either), but only Hämophilus influenzae resp. H. parainfluenzae.
And once a year a sputum investigation is performed at the rehabilitation hospital, where until now never a Pseudmonas has been detected either or another germ except the normal flora.
The Pseudomonas at the other laboratories is mostly found in small numbers, the Haemophilus always in great numbers. It has to be mentioned, that the laboratory of my general practitioner is screening also for Pseuomonas.
The Hämophilus is only found in the laboratory of my GP, in the other labs it has until now never been detected.
Now my questions:
How can this course be judged?
First of all there is the question of a chronic colonization with Pseudmonas yes or no.
And furthermore I am wondering, if one should probably take something into account with the sputum samples.
Or are there such great differences between the laboratories concerning the technique of investigation?
The last question is, if it is possible that the Hämophilus smoothes the way for the Pseudmonas? Because the Hämophilus is always detectable in the suputum investigation from may, the Pseudmonas of the laboratory of the CF-center respect. of the pulmonologist is detectable in june-august. 2-3 times a year an i.v. antibiotic therapy is performed and continously now the intake of azithromycin.
Many thanks for your efforts and answer

Answer

Hello,
you mention 2 problems with your question:
1. The comparability of results, which have been measured in different microbiological laboratories. Especially the detection of germs out of materials from CF patients represents a special challenge for the laboratories. The normal routine bacteriological investigation is not sufficient to diagnose securely CF-relevant germs. Therefore it may be possible, that laboratories which have few or no experience in the diagnostic of CF-materials, do not detect some germs securely, do not recognize them or falsly detect them. Actaully those laboratories, which handle those complicated materials, should be trained especially for those diagnostics. Until now it is not mandatory, that laboratories, which handle CF-materials and diagnose the bacteria out of these, perform a regular CF-relevant quality control. Unfortunately there are no binding quality controls, yet. Dr. Hogardt, an expereienced microbiologist from Munich, did already perform several of those quality controls with large microbiological institutes.

2. On the other hand it might also be that the Pseudomonas germs are indeed not detectable in every sputum. Especially if inbetween antibiotic therapies are performed, the germs can not be detected for a certain period of time. Often they are present then in such a low number, that the detection with the standard methods of the bacterial diagnostics is not successfull.

Therefore I would assume in your case that you are colonized chronically with Pseudmonas.

Hämophilus influenzae is generally detected in young patients frequently. The role of Hämophilus influenzae in CF is not yet clarified securely.
With best regards,
Barbara Kahl

03.08.2009