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virology -5 - shiney - Printable Version +- USMLE Forum - Largest USMLE Community (https://www.usmleforum.com) +-- Forum: USMLE Forum (https://www.usmleforum.com/forumdisplay.php?fid=1) +--- Forum: Step 1 (https://www.usmleforum.com/forumdisplay.php?fid=2) +--- Thread: virology -5 - shiney (/showthread.php?tid=239875) |
virology -5 - shiney - ArchivalUser - 11-06-2007 pregnant southeast Asian immigrant presents for prenatal care. Her past medical history is significant for a severe illness 3 years ago characterized by fatigue, nausea, anorexia, vomiting, jaundice, joint pains, and generalized skin lesions that slowly disappeared. She has felt well recently. Which of the following laboratory tests should be ordered to investigate the patient's past illness? A. Hepatitis B surface antigen (HBsAg) B. IgG cytomegalovirus (CMV) antibody levels C. IgM antibody to HBsAg D. IgM antibody to hepatitis B core antigen E. Quantitation of hepatitis A virus (HAV) IgM antibody 0 - ArchivalUser - 11-06-2007 cc? 0 - ArchivalUser - 11-06-2007 noo 0 - ArchivalUser - 11-06-2007 bb 0 - ArchivalUser - 11-06-2007 no! one more try 0 - ArchivalUser - 11-06-2007 okay here is the answer, The correct answer is A. The clinical signs suggest that this woman had hepatitis B three years ago and the fact that she is now feeling better also suggests that she recovered from this infection. Since she is pregnant, it is necessary to find out if she still has the organism in her liver (chronic hepatitis B infection) by performing a test for HBsAg. This test will be negative if she has completely recovered from the disease, but it would be positive if she is a chronic carrier. The clinical signs of the disease she had 3 years ago do not match those of CMV (choice B), and CMV does not produce chronic infections. Measurement of IgM antibody to hepatitis B core antigen (choice D) would be of no value at this time. This antibody is positive in acute cases of hepatitis B, but would no longer be positive in this case. Measurement of IgM anti-hepatitis B core antigen is one of the most important tests in the hepatitis profile because the appearance of the antibody correlates with the disappearance of HBsAg. Examination of IgM antibody to HBsAg (choice C) would be of no value at this time. This IgM antibody would be formed early during the recovery from acute hepatitis B, and would class switch to IgG later on in the disease. Quantitation of hepatitis A virus (HAV) IgM antibody (choice E) would be useless, since hepatitis A virus (HAV) only causes acute infectio 0 - ArchivalUser - 11-06-2007 nice explanation Shiney thanks... 0 - ArchivalUser - 11-06-2007 welcome!! |