Exam 3 PQ_3 PDF

Lecture 20 & 21 1.Choose the assay that is BEST described by each statement. Each assay can be used once, more than once, or not at all. Detects patient antibodies by using a fluorescently-labeled secondary antibody IFA Reaction between an insoluble antigen and a soluble antibody visualized o...

Lecture 20 & 21 1.Choose the assay that is BEST described by each statement. Each assay can be used once, more than once, or not at all. Detects patient antibodies by using a fluorescently-labeled secondary antibody IFA Reaction between an insoluble antigen and a soluble antibody visualized on a test card Latex agglutination Detects patient antibodies by using an agar plate Double immunodiffusion 2. In a hemagglutination assay to detect anti-RBC antibodies performed in a 96-well microtiter plate, what does it mean if a patient is determined to have a titer of 32? 32 wells were positive for agglutination. The last well that showed agglutination was well number 32. The last well that showed agglutination had antibody that was diluted 1/32. The patient is 32 years of age. 3. You are typing a patient’s blood using tubes. Tube 1 contains an antibody to blood group antigen A, tube 2 contains an antibody to blood group antigen B, and tube 3 contains buffer only. You mix a sample of the patient’s blood into each tube and observe the tubes after a few minutes. Since all three tubes look identical, you conclude that the patient is most likely what blood type? Type A Type B Type AB Type O 4. You are developing an indirect ELISA for the detection of human serum IgG antibody to epidermal growth factor. You start by coating your microtiter plate with EGF and then add patient serum. What detection mechanism will you use (i.e, what will be added next to your reaction) to determine if anti- EGF antibodies are present in the patient’s serum? enzyme-labeled Fab fragments enzyme-labeled recombinant EGF enzyme-labeled EGF enzyme-labeled monoclonal antibody to EGF enzyme-labeled anti-human IgG 5. Which of the following statements is TRUE regarding precipitation and/or agglutination reactions? Monoclonal antibodies can be used in agglutination assays but not precipitation assays. A precipitation reaction can only be used to detect antibodies, but an agglutination reaction can be modified to detect either antigen or antibody. A precipitin line forms when patient antibodies bind to bacterial cells on an agar plate. The appropriate concentrations of antibody and antigen required for precipitation reactions are found in the equivalence zone. 6. Immunoblotting (western blotting) is a technique that was previously used as a confirmatory test to detect the presence of antibodies against HIV in a patient’s serum. The procedure involves separation of HIV proteins in an acrylamide gel and transfer of these separated proteins onto a membrane. The membrane is then incubated with primary (1o) antibody followed by incubation with labeled secondary (2o) antibody. What are the 1o and 2o antibodies for this HIV western blot? (Options A-C are written 1o antibody; 2o antibody.) Correct answer: Patient serum antibodies; Anti-human IgG anti-human IgG; Anti-HIV antibodies Anti-HIV antibodies; Patient serum antibodies 7. The goal of the North Pole Department of Health is to reduce morbidity caused by "Reindeeritis". A new rapid diagnostic assay is developed by DetectEmAll Diagnostics Laboratory to accurately identify elves that have been exposed to infected reindeer. The diagnostic assay was performed on 1000 elves, with a confirmatory PCR performed to definitively determine each elf's disease status. The results are in the following table. What is the approximate sensitivity of this rapid diagnostic assay? 3% 35% 65% 90% (350/385) 98% 8. Quantitative PCR (qPCR) was performed on six patients (A-F) suspected of being infected with a novel DNA virus. Primers specific for this virus were used and 45 cycles performed. The amplification plots are shown below. Which of the following patients has the highest viral load (amount of virus) in the sample tested? Patient A (The lowest CT value = highest amount of virus (or viral DNA) Patient B Patient C Patient D Patient E Patient F 9. Using the amplification plots in the above question, what is the approximate CT value for Patient B? 25 28 (The CT value is where the curve crosses the threshold line.) 32 35 42 10. A latex agglutination test is performed on five patients (1-5) suspected of having a strep throat infection. Throat swabs of tonsillar exudate are obtained and bacterial antigens are extracted from the swab and mixed with antistreptococcal antigens conjugated to blue latex beads. Results from each patient are shown below. Which patient or patients have a strong positive test result? Patient 1 Patient 2 Patient 3 Patient 4 Patient 5 Patients 1, 3, 4 and 5 11. You wish to use a molecular assay to detect the presence of a novel bacterium, Bacterium grossium that was isolated from a patient's stool. You design a primer set for amplifying a 400 bp region of the DNA encoding one of the bacterial surface proteins. After the reaction, you run an aliquot of the reaction on an agarose gel, and detect a band at 400 bp, and you conclude that this bacterium was in the patient's stool sample. What assay was performed to make this determination? PCR (This was a qualitative assay and no need to convert RNA to DNA.) RT-PCR qPCR qRT-PCR 12. Serum from six patients suspected of an autoimmune disease were tested for autoantibodies to nuclear antigens using a double immunodiffusion assay (shown, below). Which patients show a positive test result? Patients 1 and 2 Patients 2 and 3 Patients 1, 2 and 3 Patients 3 and 6 Patients 4 and 5 Patients 3, 4, 5 and 6 13. A hemagglutination assay is performed on 6 patients (rows 1-6) suspected of having a viral pneumonia. Titer values are listed across the top for each column. What is the antibody titer of patient 6? 8 64 128 256 2048 16384 14. In the assay from Question 13, which patient has the highest concentration of anti-viral antibodies in his/her serum? Patient 1 Patient 2 Patient 3 Patient 4 Patient 5 Patient 6