Cryptococcal antigen

Use(s):

Diagnosis of cryptococcal meningitis, systemic cryptococcosis in both immunocompetent and immunocompromised patients.

Description:

Determination of the presence of cryptococcal antigen and the titre in the specimen, by lateral flow device.

Specimen:

Serum or CSF, 200 µl minimum or 3 mL clotted blood.

Results:

Negative, Positive (titre).

95% Turnaround Time:

1 days

 

Cryptococcal antigen testing

 At the Mycology Reference Centre, up until 1/4/14 we tested for Cryptoccal antigen using a latex agglutination method (Immy, Latex Agglutination) carrying out a full titration on all positive samples in all cases. From 1/4/14 we changed to the lateral flow device (Immy, LFD) and are screening all samples at 1:2 and 1:100. There is some evidence that the LFD method is slightly more sensitive than the LA and we find it is easier to find the endpoint to titrations. Due to the increased cost of the LFD we have decided to offer a Cryptococcal antigen screen - testing at 1:2 and 1:100 only, and if required by the service user a full Cryptococcal antigen titration to a negative endpoint which is an additional fee (please enquire). In all cases of positive screen results, the service users will be contacted to determine if they require a full titration or not and we are able to discuss with users the usefulness of a titration in the management of patients.

The LFD gives a higher titre than the LA and this makes comparisons between results from the two methods difficult. However, we have plotted below the data from our comparison of the two methods and it is clear we find an approximately 10 fold increase in the LFD titre compared to the LA titre.

 


Page Reviewed: 02/07/19 | Updated by: Kevin Roberts