This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hepatitis Viruses, Subject name: Microbiology
Hepatitis A virus is best diagnosed by: 
Select and explain. 
A. IgM antibodies in serum, B. Isolation from stool, C. Culture from blood, D. Isolation from bile
A: IgM antibodies in serum
Answer: A: IgM antibodies in serum 
Explanation: Ans. is 'a' i.e., IgM antibodies in serum (Ref: 19th/e, Harrison, 2004)"Detection of IgMspecific anti -HAV in the blood of an acutely infected patient confirms the diagnosis of hepatitis A." HAV is the only cultivable hepatitis virus. Diagnosis is based on IgM detection due to the early presence of these antibodies in patient serum, in fact so early that a lack of hepatitis A antibodies at the onset of clinical manifestations excludes hepatitis A.