The Cryptococcus Antigen Latex Agglutination System is a qualitative and semi-quantitative test system for the detection of capsular polysaccharide antigens of Cryptococcus neoformans. Monitoring of the antigen titer may be useful during therapy, as clinical improvement is usually accompanied by a decrease in antigen titer.
Latex agglutination test has both diagnostic and prognostic value since progressive disease is usually accompanied by increasing antigen titers. Declining titers are usually associated with clinical improvement, with or without therapy. Inadequate therapy is indicated by stationary or rising titers on subsequent, sequential specimens. Cryptococcus antigen in the body fluids of the untreated patient indicates active infection. However, in some treated patients, titers remain positive at low levels for extended periods during which the organism can no longer be demonstrated.
The result is not intended to be used as the sole means for clinical diagnosis or patient management decisions. Although the test sensitivity and specificity are high overall, false positives and false negatives may be observed. False negatives are more common with localized disease. Titers of up to 200 have been observed in cats without demonstrable overt cryptococcosis. High protein levels can cause interference.
Interfering Substance: Severely elevated immunoglobulin concentrations such as seen with multiple myeloma.
Cross Reactivity/False Positive: Low: Trichosporon (trichosporonosis)
Testing is performed Monday – Saturday
Results released: 24 hours
Specimen: Serum, CSF
Serum: Collect serum specimens in serum separator tube. Allow blood to clot for 30 minutes, then centrifuge. Send serum in serum separator tube or transfer tube
CSF: Leak-proof transport tube
Volume: 0.25 mL
Stability: Room temperature = 7 days, Refrigerated = 2 months, Frozen = indefinite
Serum types other than serum or CSF
Overnight or 2nd day – ambient or with cold pack