What is Babesia microti IgM antibody by indirect immunofluorescence assay?
Indirect immunofluorescence uses Babesia microti-infected erythrocytes fixed to a slide as antigen; patient serum is layered on, and bound human IgM is visualised with a fluorescein-labelled anti-IgM conjugate read by a technologist. IgM is the first isotype to appear after infection of red cells by the intra-erythrocytic parasite, typically within the first one to two weeks of symptomatic babesiosis, and generally wanes over weeks to a few months. Because the read-out is a visually scored endpoint dilution rather than a quantified concentration, inter-observer and inter-laboratory variation is inherent to the method.