Laboratory Testing Basics
What is the primary purpose of laboratory testing for viral infections?
To diagnose and monitor viral infections.
What does ELISA stand for?
Enzyme-linked immunosorbent assay.
What does RT-PCR stand for?
Reverse transcriptase polymerase chain reaction.
What does flow cytometry measure in viral diagnostics?
Cell populations, such as CD4+ T cells.
Which viral test is commonly used for monitoring immune status in HIV patients?
Flow cytometry.
What is one example of a common viral diagnostic test?
ELISA, RT-PCR, flow cytometry, etc.
What does ELISA detect in a patient’s sample?
Antibodies or antigens.
What is the main function of reverse transcriptase in RT-PCR?
Converting RNA into complementary DNA (cDNA).
What type of labeled molecules are used in flow cytometry?
Fluorescently labeled antibodies.
Which test is most suitable for detecting an ongoing viral infection?
RT-PCR.
Define the term “sensitivity” in the context of viral diagnostic tests.
The ability of a test to correctly identify those with the disease (true positives.
What is the main principle of ELISA?
The detection of antigen-antibody interactions using enzyme-linked reactions.
What is the purpose of thermal cycling in PCR?
To amplify specific DNA sequences through repeated cycles of denaturation, annealing, and extension.
What is the significance of forward scatter (FSC) in flow cytometry?
It indicates cell size.
Which test is often used to screen for the presence of antibodies to a virus?
ELISA.
Define “specificity” in the context of diagnostic testing.
The ability of a test to correctly identify those without the disease (true negatives).
Name one advantage and one disadvantage of ELISA.
High sensitivity (advantage) and limited to known targets (disadvantage).
Why is RT-PCR considered a highly sensitive diagnostic tool for viral infections?
Because it can detect even small amounts of viral RNA.
What is the role of side scatter (SSC) in flow cytometry?
It measures the internal complexity or granularity of cells.
Which test is considered the gold standard for viral load quantification?
RT-PCR.
Name three factors that influence the accuracy of viral diagnostic tests.
The sample quality, timing of sample collection, and test specificity/sensitivity.
Describe the difference between a direct and an indirect ELISA.
A direct ELISA detects antigens directly using labeled antibodies, while an indirect ELISA uses a secondary antibody for detection.
Describe one limitation of RT-PCR in viral diagnosis.
The inability to distinguish between active and inactive virus?
Why is monitoring CD4+ counts important in the context of HIV?
To assess immune function and track disease progression.
Provide an example of when a combination of ELISA, RT-PCR, and flow cytometry might be used in clinical practice.
Monitoring HIV progression by detecting antibodies (ELISA), quantifying viral load (RT-PCR), and assessing immune function (flow cytometry).