Gary Lum wrote:
> I wouldn't say sputum for microscopy, culture and
> susceptibility testing is always useless. But pretty
> close to useless in some contexts. Even if you screen
> using a Gram's stain and try to correlate the microscopy
> with the culture result, the vast majority of specimens we
> receive (hospital and community work) aren't particularly
> clinically useful in terms of results. Whereas someone
> with clinical signs and symptoms of acute pneumonia with a
> consistent chest x-ray is pretty informative. It's horses
> for course, I'd never dismiss the value of a well
> collected sputum in a patient actually productive of
> sputum, however, the clinical, radiological and
> microbiological information all have to be interpreted
> together. In our area where melioidosis is common, the
> chest x-ray is important, but it's the culture that's
> vital. However, we frequently receive poorly collected
> collected specimens and the microscopy does not reveal the
> typical gram-negative safety-pin shaped bacillus with
> bipolar staining consistent with Burkholderia
> pseudomallei. Given the most common cause of pneumonia
> worldwide is Streptococcus pneumoniæ and that laboratories
> are pretty poor at culturing the organism from well
> collected sputa, it's no wonder some requesting medical
> practitioners dismiss the value of sputum for m/c/s.
About half the samples we receive in our lab are useless
too. Bad instructions, bad techniques.
Missing Str. pneumoniae could be a matter of bad technique
too. We wash purulent bits of sputum in saline to remove
saliva etc. and then culture aerobically and anaerobically.
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