viral lab diagnosis. viral lab diagnosis.pptx

viral lab diagnosis.pptx viral lab diagnosis.pptx viral lab diagnosis.pptx
viral lab diagnosis.pptx

1. LABORATORY DIAGNOSIS DR. ALIYA ZAMAN

2. INTRODUCTION There are five approaches to the diagnosis of viral diseases by using clinical specimens : Identification of the virus in cell culture M icroscopic identification directly in the specimen S erologic procedures to detect a rise in antibody titer or the presence of IgM anti body D etection of viral antigens in blood or body fluids D etection 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.

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

6. 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 .

7. 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.

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

9. 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.

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

11. 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 .

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

13. MICROSCOPIC IDENTIFICATION

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

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

16. SEROLOGIC PROCEDURES

17. 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

18. 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 .

19. DETECTION OF VIRAL ANTIGEN

20. 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.

21. DETECTION OF VIRAL NUCLEIC ACIDS

22. 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.

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