MCQs: VZV laboratory testing: Answers

1) VZV IgM serology is a sensitive means of picking up acute infection. T/F

False: Several false negative results occur from VZV IgM testing. Many labs no longer offer the assay.

2) Most people who don’t have a clinical history of chickenpox have negative VZV IgG on laboratory testing? T/F

False: Most people (80%+) who have no clinical history of chickenpox actually have VZV IgG antibodies on lab testing and are thus immune.

3) IgG seroconversion can more reliably be detected after VZV vaccination as opposed to natural infection? T/F

False: Natural infection produces the strongest IgG response. False negative IgG results occasionally produced after vaccination.

4) PCR can potentially be used to discriminate between vaccination and wild type strains of VZV? T/F

True: PCR genotyping can potentially discriminate if the assay is designed for this purpose.

5) Cotton is a better material than polyester at picking up VZV virus? T/F

False: Polyester is a better material than cotton and is recommended in viral PCR swabs.

6) When the rash has crusted over, the PCR is ineffective at picking up VZV? T/F

False: Crusts contain high levels of virus and OCR is usually effective at testing this specimen type.

7) PCR is an effective method of distinguishing between a chickenpox and a shingles rash? T/F

False: It is the same virus, so PCR will not discriminate between the two clinical entities.

8) VZV Immunofluorescence is commonly used in laboratories to make the diagnosis of chickenpox? T/F

False: It certainly can be used, but in my experience, is certainly not common amongst routine diagnostic laboratories for the diagnosis of VZV.

9) VZV is able to be cultured on cell lines? T/F

True: but with poor sensitivity. Viralculture now rarely used to make a diahnosis of VZV in diagnostic laboratories.

10) Electron microscopy can discriminate between VZV and Herpes Simplex Virus (HSV)? T/F

False: The two viruses look the same on electron microscopy.


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