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Answers to Multiple Choice Questions - Paper 2

 

Instructions for candidates

The examination consists of 30 multiple choice questions, each divided into 5 different parts. Each part contains a statement which could be true or false. Each question will have at least one part which is true. For each part, you should indicate whether you think it is true (T), false (F), or don’t know (DN). You must fill in the relevant square with a black pen. One mark will be given for each correct answer and one mark deducted for each incorrect answer. You will not be marked for those questions for which you have indicated "don’t know".
 

  1. Viruses may contain
True DNA
True RNA
True Glycoprotein
True Enzymes
False Cell wall
 Comments Viruses may contain either DNA, or RNA. They may contain enzymes such as polymerases, and have glycoproteins in their envelope
   
  2. Viruses are
True Obligate intracellular parasites
False May divide by binary fission
False Have their own metabolism
True  May contain enzymes for replication
True  May have an envelope
 Comments Unlike bacteria, viruses do not have their own metabolism and do not divide by binary fission. They are intracellular parasites and may contain enzymes for their replication. Some viruses possess a lipid envelope.
   
  3. The following statements are true
False All viruses are sensitive to antiviral agents
True  Virus infected cells may be transformed.
True  Viruses may have a lipid envelope
True  Viruses may produce cytopathic changes in cell culture
True  Some viruses are destroyed by lipid solvents
 Comments To date, only a few viruses can be treated by antiviral agents. Some viruses such as oncornaviruses can transform cells. Some may have a lipid envelope which may be destroyed by lipid solvents.
   
  4. The following are direct detection methods
True  Detection of rotavirus antigen in faecal specimens
False Single radial haemolysis (SRH)
False  CMV DEAFF test
True  Electron microscopy
True Polymerase chain reaction
 Comments SRH is a serological assay, and the CMV DEAFF test is a rapid culture test. The rest are used to detect virus particles, antigens, and nucleic acid directly from a specimen
   
  5. The following methods may be used for serological diagnosis
True  Complement-fixation tests (CFT)
False  Polymerase chain reaction (PCR)
True  Single Radial Haemolysis (SRH)
False  CMV DEAFF test
True Western blot
Comments PCR detects viral genomes directly. The CMV DEAFF test is a rapid culture assay. Western blot is mainly used as a serological test


 
 

  6. A serological diagnosis of a primary viral infection may be made
False  Detection of viral-specific IgA
False  Detection of viral-specific IgD
False  Detection of viral-specific IgE
True  Detection of viral-specific IgM
True Seroconversion
 Comments  A diagnosis of a primary viral infection may be made by the detection of IgM and/or seroconversion.
   
 
  • 7. The following are examples of viral genome detection (molecular methods)
  • True  Southern blot
    False  Western blot
    False  RIBA (Recombinant immunoblot assay)
    True  Branched DNA
    True  Polymerase chain reaction (PCR)
    Comments  Southern blot, branched DNA, and PCR are viral genome detection methods. Western blot and RIBA are serological assays
       
      8. The following statements are true
    False  For cytomegalovirus (CMV), the cytopathic (CPE) effect usually appears within 24-48 hours
    True  For some viruses, the CPE is so characteristic that so further identification is required.
    True  Paramyxovirus causes syncytia formation in cell culture
    False  A given virus always produce identical CPE in different cell cultures
    True  Immmunofluroescence may be used to identify a virus in cell culture
     Comments  It takes 1-3 weeks for CMV-specific CPE to appear. For some viruses such as herpes simplex, the CPE is so characteristic that so further identification is required.
       
      9. Poliovirus can be typed by 
    False  Single radial haemolysis (SRH)
    False  Haemagglutination inhibition test (HAI)
    False  DEAFF test
    True  Neutralization test
    True  Hybridization with specific nucleic acid probes
     Comments Polioviruses can be typed by neutralization tests and hybridization with specific nucleic acid probes. SRH and  HAI are not used. The DEAFF test is used for the isolation of CMV
       
     
  • 10. Immunofluorescence techniques can be used to detect the following directly from the specimen.
  • True  Chlamydia
    True  CMV
    True  Respiratory Syncytial Virus (RSV)
    True  Influenza virus
    True  Rabies virus
    Comments All the above


     
     

     
  • 11. The following statements are true for the haemagglutination-inhibition (HAI) test.
  • False  Not a quantitative test
    True  Treatment of patient serum is necessary to remove non-specific inhibitors
    True  Animal blood is necessary
    True  Usually more specific than complement fixation tests (CFT)
    True  May be used for the diagnosis of rubella infection
     Comments  HAI is a quantitative test. It is widely used in rubella serology. It is usually more specific than CFT. Treatment of patient serum is necessary to remove non-specific inhibitors.
       
      12. Regarding cell culture
    False  Viruses can only be cultured using cell lines
    False  The presence of cytopathic effect is the only way to detect a virus
    True  The neutralization test is the mainstay of identification of a poliovirus isolate
    False  The haemagglutination inhibition test is the mainstay of identification of a respiratory syncytial virus (RSV) isolate
    False  Whole blood is the specimen of choice for many common viruses
     Comments  Viruses may also be cultured in eggs and animals. The presence of virus may be detected by CPE as well as haemadsoption, and presence of viral particles and antigen. 
       
      13. A standard Polymerase Chain Reaction (PCR) consists of
    False  Denaturation, annealing, and ligation steps
    True  Denaturation, annealing, and extension steps
    True  dNTPs
    True  Mg++ ions
    True  Taq polymerase
    Comments  Denaturation, annealing, and ligation steps occur in LCR. PCR consists of Denaturation, annealing, and extension steps. It requires dNTP, Mg++, taq polymerase, and target-specific oligonucleotide primers.
       
      14. Modification of a standard PCR include
    True  Nested PCR
    False  branched DNA (bDNA)
    True  RT-PCR (Reverse transcription PCR)
    True  Quantitative PCR
    False  3SR (Isothermal amplification)
     Comments  Nested PCR, RT-PCR and quantitative PCR are modifications of the PCR protocol. bDNA and 3SR are alternative amplification techniques.
       
      15. Safety measures for preventing PCR contamination include
    True  The use of uracil-N-glycosylase (UNG)
    True  Use of filtered pipette tips
    True  Separate areas for master mix, template, and PCR product operation
    True  Dedicated pipettes for master mix, template, and PCR products
    True  Ultraviolet irradiation
     Comments  All the above may be useful in preventing contamination of PCR.


     
     

      16. The following statements are usually true
    True  PCR is more sensitive than branched DNA assays
    False Branched DNA is more sensitive than Ligase chain reaction
    True  Exponential amplification occurs in PCR
    True  Linear amplification occurs in branched DNA
    True  PCR is extremely liable to contamination
     Comments  Exponential amplification occurs in PCR, LCR and NASBA/3SR. Therefore these techniques are extremely liable to contamination and are more sensitive than branched DNA, where linear amplification occurs.
       
      17. Laboratory diagnosis of infectious mononucleosis include
    True  Detection of VCA-IgM
    False Detection of VCA-IgA
    False Seroconversion against EBNA
    True  Paul-Bunell test
    True  VCA IgG avidity test
     Comments
     
     
     Diagnosis of infectious mononucleosis is usually made by the Paul-Bunell where heterophil antibodies are detected and by the detection of EBV-IgM. VCA-IgG avidity test may be used to confirm equivocal cases. Detection of elevated titres of VCA-IgA correlates with an increased risk for nasopharyngeal carcinoma and is used as a screening test. Seroconversion against EBNA does not take place until months after the initial illness.
       
     
  • 18. Viruses that routinely establish latent infections in human sensory ganglia include
  • False Epstein-Barr virus
    True  Herpes Simplex Virus type 1
    True  Varicella-Zoster Virus
    True  Herpes Simplex Virus type 2
    False Human herpesvirus 6
     Comments  All the above herpesviruses can cause latent infections. However, only HSV 1+2, and VZV routinely establish latent infections in human sensory ganglia.
       
      19. Rapid diagnosis of CMV disease include
    True CMV pp65 antigenaemia 
    False Conventional cell culture
    True  DEAFF test
    True  Detection of CMV-DNA in blood by PCR
    False Rising antibody titres
    Comments  Rapid diagnosis of CMV disease include CMV pp65 antigenaemia, DEAFF test, and Detection of CMV-DNA in blood by PCR.
      20. The following viruses are associated with respiratory infections
    False Rotaviruses
    True  Adenoviruses
    True Influenza viruses
    False HTLV-1
    True RSV
     Comments  Rotaviruses cause diarrhoea. HTLV-1 is associated with adult T-cell leukaemia and tropical spastic paraparesis.


     
     

      21. The following viruses are thought to cause gastroenteritis 
    False Enteroviruses
    True Adenoviruses
    True Norwalk-like viruses
    True Astroviruses
    True Rotaviruses
     Comments  Although enteroviruses may be found in faeces, they are not associated with gastroenteritis. The other viruses are associated with gastroenteritis.
       
      22. The following viruses are transmitted from animals to humans
    True  Influenza A H5N1
    False HTLV-1
    True  Hantaviruses
    False Poliomyelitis
    True  Rabies
    Comments  Influenza A H5N1 is otherwise known as the "bird flu" It afflicted Hong Kong in late 1997 and was transmitted from poultry to humans. Hantaviruses is transmitted from rodents to humans and rabies can be transmitted from various mammals to humans. 
       
      23. A chronic carrier state may occur in the following:
    False  Hepatitis A 
    True Hepatitis B
    True Hepatitis C
    True Hepatitis Delta
    False  Hepatitis E
     Comments A chronic carrier state can exist in hepatitis B, C and Delta Virus infections
       
      24. The following viruses are transmitted by blood
    False  Rubella
    True  HIV
    False  Measles
    True  HBV
    True  HCV
     Comments  HIV, HBV and HCV are transmitted by blood. Rubella and measles are transmitted via respiratory droplets
       
     
  • 25. The following may be useful for prognostic purposes in HIV-infected individuals 
  • False  HIV envelope antibody
    True HIV-p24 antigen
    True CD4 count
    False  CD8 count
    True  HIV viral load
     Comments  HIV envelope antibody remains high throughout the course of HIV infections and thus does not carry any prognostic value. HIV-p24 antigen had been widely used in the past as a prognostic marker but it has been superseded by HIV viral load. CD4 count plays an important role in telling us what stage the disease is at.


     
     

     
  • 26. The following markers are usually present in a hepatitis B carrier with chronic active hepatitis
  • True  HbsAg
    False HbsAb
    False Anti-HBc IgM
    True  HBV-DNA
    True  HbeAg
     Comments  In patients with chronic active hepatitis, HBV replication is present and hence HBV-DNA and HbeAg. HbsAg is present. Anti-HbcIgM is normally absent although it may occasionally be detected during periods of exacerbations.
       
      27. Regarding viral infection of the central nervous system (CNS)
    True Meningitis may occur together with encephalitis
    True Enteroviruses are one of the commonest causes of CNS infections in childhood
    False  Electron microscopy of the cerebrospinal fluid (CSF) is a useful diagnostic test
    False PCR has no role in the diagnosis of CNS infections
    True The detection of antibody in the CSF is a useful diagnostic marker
     Comments  Meningitis usually occurs together with encephalitis. Enteroviruses are one of the commonest causes of CNS infections in childhood. Electron microscopy is too insensitive to be useful as a diagnostic test. PCR assays for HSV are now routinely used for the diagnosis of herpes simplex encephalitis. The detection of antibody in the CSF is a useful diagnostic marker
       
      28. Regarding rash illnesses
    True  Varicella-zoster virus (VZV) infection may cause a vesicular rash 
    False The rash caused by parvovirus B19 is due to the presence of virus in the skin
    False Measles is usually diagnosed by viral culture
    True  Herpes simplex virus (HSV) infection is usually diagnosed by viral culture
    False  VZV cannot be grown in cell culture
     Comments  Varicella-zoster virus (VZV) infection may cause a vesicular rash. The rash caused by parvovirus B19 is probably an allergic reaction due to the deposition of immune complexes. Measles is usually diagnosed by serology. Herpes simplex virus (HSV) infection is usually diagnosed by viral culture. VZV can be grown in cell culture although this is rarely used for diagnosis.
       
      29. Rubella infection
    True  Can be asymptomatic
    True  May be indistinguishable from parvovirus B19
    False  Can have serious side effects when occurring in a woman in the third trimester of pregnancy
    True  Is usually preventable by vaccination
    True  May be acquired by having close contact with an infant with congenital rubella syndrome
     Comments  Rubella infection can be asymptomatic. It may be indistinguishable clinically from parvovirus B19 infection. The most serious effects occur when a pregnant woman is infected in the first trimester of pregnancy. It is usually preventable by vaccination. Infants with congenital rubella syndrome pose a great infectious risk since they may excrete virus in great quantities up to 1 year of age.
       
      30. Regarding laboratory tests for rubella
    True  Rubella immunity may be determined by an enzyme immunoassay
    False CFT is commonly used for the diagnosis of acute infection
    True  IgM antibody is usually detectable after the onset of rash 
    False Rubella virus cannot be cultured
    False Pre-natal diagnosis of rubella in a foetus is simple and reliable
     Comments  Rubella immunity may be determined by an enzyme immunoassay. CFT is not commonly used for the diagnosis of rubella infection; Haemagglutination-inhibition tests are. IgM antibody is usually detectable after the onset of rash Rubella virus can be cultured although this is rarely used as a method of diagnosis. Pre-natal diagnosis of rubella in a foetus such as amniocentesis involve some degree of risk to the fetus.

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