Leptospirosis is a zoonotic disease (spreads from animals to humans) caused by different serovars of the bacterium Leptospira interrogans.  You are a vet who has been treating a lot of animals lately with the disease.  You are not feeling very well, you see your GP who takes a blood sample and sends it off to look for IgM antibodies to L. interrogans  (the presence of antibodies would mean you have leptospirosis). The lab uses an agglutination assay to detect IgM antibodies to L. interrogans (they use latex beads coated with a specific antigen to L interrogans and mixes it with the serum sample from the patient).  

Your sample is shown in panel A.  Do you have leptospirosis?