What is Crithidia luciliae and what is its relevance to the diagnosis of SLE?
Crithidia luciliae is a parasite that uses the housefly as its host. It contains a kinetoplast, a modified mitochondria that contains a dense collection of circularized dsDNA that can be utilized as a substrate alongside patient serum for the detection of antibodies to dsDNA. The intact circular DNA is free of loose strands of ssDNA and other nuclear antigens, and is more resistant to becoming denatured than DNA in plastic ELISA wells.
These attributes improve the specificity of the test (98%–100%) to detect antibodies to dsDNA compared with other methods, although at a lower sensitivity (50%–55%).
Testing is performed by IIF, often referred to as CLIFT, Crithidia luciliae indirect fluorescent test.
What is the relevance of Crithidia luciliae to the diagnosis of SLE
This test may be useful in situations where clinical suspicion for lupus is low but prior testing reveals low titer dsDNA antibody by other methods.