The document discusses five main approaches for diagnosing viral diseases through clinical specimens: identification in cell culture, microscopic identification, serologic procedures, detection of viral antigens, and detection of viral nucleic acids. Each method employs specific techniques to confirm the presence of viruses, such as using known antibodies, microscopy, or PCR. The information provided outlines the importance of rapid diagnosis and various testing methods to aid in clinical practice.

1. LABORATORY
DIAGNOSIS
DR. ALIYA ZAMAN

2. INTRODUCTION
There are five approaches to the diagnosis of viral diseases by using
clinical specimens:
i. Identification of the virus in cell culture
ii. Microscopic identification directly in the specimen
iii. Serologic procedures to detect a rise in antibody titer or the presence
of IgM anti body
iv. Detection of viral antigens in blood or body fluids
v. Detection of viral nucleic acids in blood or the patient’s cells

3. IDENTIFICATION IN CELL CULTURE

4. IDENTIFICATION IN CELL CULTURE
 Cell cultures are used to grow
it is important to introduce into the cell culture as soon as possible.
Brief transport or storage at 4 degrees Celsius is acceptable.
 When viruses grow in cell cultures, they often cause noticeable changes in the
cells, known as the cytopathic effect (CPE).
This effect can show up as changes in cell size and shape or merging of cells
into larger, multi-nucleus cells called syncytia.
These changes usually mean the cells are dying or have already died.

6. IDENTIFICATION IN CELL CULTURE
Other methods
i. Hem adsorption: Check if red blood cells stick to infected cells.
This works for viruses like mumps and influenza.
ii. CPE Interference: Some viruses, like rubella, can be detected
by how they affect the CPE of other viruses, such as echovirus.
iii. Acid Detection: Infected cells produce less acid, changing the
color of a pH indicator in the culture medium. This helps identify
certain enteroviruses.

7. IDENTIFICATION IN CELL CULTURE
To definitively identify a virus in cell culture, specific tests using
known antibodies are used.
i. Complement Fixation: If the virus and antibody match, they
bind together, preventing a reaction with red blood cells and
showing that the virus is present.

8. IDENTIFICATION IN CELL CULTURE
ii. Hemagglutination Inhibition: If the virus and antibody
match, the virus can't clump red blood cells, indicating the virus’s
presence.

9. IDENTIFICATION IN CELL CULTURE
iii. Neutralization: If the virus and antibody match, the antibody
blocks the virus from entering cells, stopping infection.

10. IDENTIFICATION IN CELL CULTURE
iv. Fluorescent Antibody Assay: If the virus and fluorescent-
tagged antibody match, the cells glow green under UV light,
showing the virus’s presence.

11. IDENTIFICATION IN CELL CULTURE
v. Radioimmunoassay: If the virus and antibody match, less
radioactive antibody binds to the virus, showing the virus’s
presence.

12. IDENTIFICATION IN CELL CULTURE
vi. ELISA: If the virus is present, it binds to a known antibody on
a surface. An enzyme-linked antibody then binds to the virus, and a
color change indicates the amount of virus.

13. IDENTIFICATION IN CELL CULTURE
vii. Immunoelectron Microscopy: If the antibody matches the
virus, virus-antibody clusters appear under an electron microscope.

14. MICROSCOPIC IDENTIFICATION

15. MICROSCOPIC IDENTIFICATION
Viruses can be detected and identified directly from clinical samples
using these methods:
i. Light Microscopy: Can show specific inclusion bodies or giant cells,
like the Tzanck smear for herpesvirus.
ii. UV Microscopy: Uses fluorescent stains to highlight viruses in
infected cells.
iii. Electron Microscopy: Visualizes and characterizes virus particles
based on their size and shape.

16. Tzanck smear is
generally used for the
diagnosis of the
pemphigus group of
autoimmune bullous
diseases and
mucocutaneous
herpesvirus infections

17. SEROLOGIC PROCEDURES

18. SEROLOGIC PROCEDURES
A rise in antibody levels can help diagnose a current viral infection.
Seroconversion occurs when antibodies to a virus (or any microbe) appear in a
patient's blood when they previously had none, meaning the blood has changed
from antibody-negative to antibody-positive.
To diagnose an infection, two blood samples are taken: one when the infection is
first suspected (acute-phase) and another 10 to 14 days later (convalescent-phase)
A single antibody test can't tell if the infection is recent or from the past

19. Other tests, like the heterophile antibody test (Monospot), can
diagnose infections such as mononucleosis. This test checks if
antibodies in the patient’s blood react with animal red blood cells,
causing clumping if the patient has been infected with Epstein–Barr
virus.

20. DETECTION OF VIRAL ANTIGEN

21. DETECTION OF VIRAL ANTIGEN
Viral antigens can be identified in a patient’s blood or other body fluids using
various tests, with the Enzyme-Linked Immunosorbent Assay (ELISA)
being one of the most commonly used methods.
ELISA is particularly effective for detecting specific viral proteins.
For instance, it is frequently used to identify the p24 antigen of human
immunodeficiency virus (HIV), which is a core protein of the virus.
ELISA can detect the surface antigen of hepatitis B virus, which is a key
protein found on the surface of the virus.
These tests help confirm the presence of the virus in the patient’s sample by
measuring the specific viral proteins.

22. DETECTION OF VIRAL NUCLEIC
ACIDS

23. DETECTION OF VIRAL NUCLEIC
ACDS
Viral nucleic acids, such as the viral genome or mRNA, can be
detected in a patient’s blood or tissues using probes made of
complementary DNA or RNA (cDNA or cRNA).
When only small amounts of viral nucleic acids are present, the
polymerase chain reaction (PCR) can be used to amplify these
nucleic acids. This technique is often employed to measure the
RNA of HIV and hepatitis C virus, or the DNA of hepatitis B
virus, in the patient’s blood. These assays, known as viral load
tests, are commonly used to track the progression of the disease
and assess the patient's prognosis.

24. THANKYOU.