Tuesday, December 14, 2010

Female With Fever, Weight Loss, Lack Of Appetite, And Periodic Difficulty Breathing

A 22-year-old female comes to the sexually transmitted disease (STD) clinic for her first visit. She tells the nurse practitioner that she has had four different sexual partners in the last six months and only one of them used a condom. She also admits that she used IV drugs on several occasions two years ago. She notes fever, weight loss, lack of appetite, and periodic difficulty breathing over the past few months. She has an HIV test performed, which is positive. The physician decides to do a confirmatory test for HIV. Which one of the following tests would the physician order? 

           A. ELISA (Enzyme-linked immunosorbent assay) 
           B. FACS ( Fluorescence activated cell sorting) 
           C. RAST (Radioallergosorbent Test) 
           D. RID (Radial immunodiffusion) 
           E. Western blot 


      The correct answer is E. The Western blot is the most appropriate test for confirmation of HIV infection. It identifies several different antibodies against HIV (anti- gp120, -gp41, -p24, and -p17). The initial HIV test this patient had was most likely an ELISA. The ELISA (choice A) can be used to detect p24 
      antibody in the patient, but is not as specific as the Western blot. 

      Fluorescence activated cell sorting (choice B) is a technique used to separate and count specific numbers and  types of cells in a sample. An example of this would be to count the number of B cells and T cells in a specific blood sample. 

      RAST testing (choice C) is used to determine the level of specific IgE present in a patient that reacts with a  specific allergen that has been applied to a disk or glass bead. 

      Radial immunodiffusion (choice D) is an excellent test used for quantitation of immunoglobulin levels in patients. This is used to determine the IgG, IgM and IgA levels in patient's serum. This test cannot be used to measure levels of IgD or IgE because these two immunoglobulins are at such low levels a more sensitive test such as RIA (radioimmunoassay) or EIA (enzyme-linked immunoassay) must be used.