Serology

It is very important to give full clinical details, including any recent exposure, travel history and onset date so that the correct tests are selected. It is not helpful to request simply “Serology” or “Virology”. The more information that is provided, the more useful the results will be.

Failure to provide relevant clinical information may introduce an unnecessary delay since such samples will be stored pending relevant clinical information. Date of onset is vitally important since a “convalescent” specimen alone may provide a spurious “significant” / “diagnostic” titre.

Where there is difficulty in selecting the appropriate investigations, it is always best to discuss with a Consultant Medical Microbiologist.

In general, all serology samples should be transported to the lab as soon as possible. If transport is delayed, refrigerate specimens.

Specimen types:

• 5ml of clotted blood (gold top) is required. Paediatric samples can be sent in a brown-capped 1.1ml microtube. Ideally a baseline specimen is collected at the start of illness for comparison with a convalescent specimen collected 10 days later to demonstrate a rising titre.
• Most PCR tests (e.g. to diagnose meningococcal infections, CMV, or HIV viral load etc.) require a 3.5ml EDTA (purple top) specimen. Paediatric samples can be sent in a purple-capped 1.1ml microtube. If in doubt, contact the Microbiology department.

Antenatal bloods for screening of infectious diseases in pregnancy are referred to Exeter for HIV, Hepatitis B and Syphilis serology.

Turnaround times for the three infectious diseases in pregnancy tests are monitored monthly. Up to date turnaround time data is available from the Pathology Quality Manager upon request.

Other serology specimens are also referred to reference laboratories for testing.

Basic “Atypical Respiratory” screen

Includes Psittacosis / Q-Fever / Mycoplasma / Influenza A + B and Metapneumovirus.
Note that Legionella serology is no longer available; a urine sample for Legionella antigen is the preferred diagnostic specimen.

Basic “PUO” screen

Best discussed with a Consultant Medical Microbiologist. In cases where bacterial infection is suspected, a CRP level may be helpful, since viral infections have little effect on CRP.

Tropical “PUO” screen

In cases of suspected “tropical” infections, it is always worthwhile discussing the case with a Consultant Medical Microbiologist, who can expedite pertinent serology and other investigations that can be tailored to the organism suspected.

Many other serological tests are available – if in doubt, contact a Consultant Medical Microbiologist for advice.