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. |
| 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 |
| True | Chlamydia |
| True | CMV |
| True | Respiratory Syncytial Virus (RSV) |
| True | Influenza virus |
| True | Rabies virus |
| Comments | All the above |
| 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. |
| 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 |
| 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. |
| 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. |
