Imperial Collage Healthcare
13 April

Notification of change in complement fixation testing practice


Notification of change in Mycoplasma pneumoniae, Chlamydia psittaci and Coxiella burnetii complement fixation testing practice, to take effect on Monday 13th of April 2015

A recent internal audit has revealed that atypical pneumonia serology is of limited clinical benefit. Complement fixation tests (CFTs) are of low specificity, and sensitivity can be reduced following antibiotic therapy. Additionally, it takes 10-14 days for CFT antibodies to become detectable, and at best this assay provides a retrospective diagnosis.

We are in the process of exploring alternative strategies for diagnosis of infection with these organisms, but in the meantime blood samples received for Mycoplasma pneumoniae, Chlamydia psittaci and Coxiella burnetii CFTs (atypical pneumonia screen), will be processed only if it is clearly specified on the request form, or on the electronic request, that the onset of symptoms was at least 10 days prior to date of sample collection. Where there is no indication of the above, the serum will not be processed but stored only.

We plan to introduce the above change during the week beginning Monday 13th of April.

If you wish to discuss please do not hesitate to contact us.

David Muir on behalf of the Department of Infection & Immunity

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