Ans. is 'b' i.e., Microscopic agglutination test History of fever, jaundice (icterus), bleeding diathesis (conjuctival suffusion) and renal dysfunction (hematuria) are suggestive of Weil's disease (severe Leptospirosis). A definite diagnosis of leptospirosis is based either on isolation of the organism from the patient or on seroconversion or a rise in antibody titer in microscopic agglutination test (MAT).