Lesson 4: Laboratory diagnosis of viral disease Flashcards
used for direct detection of viruses
- electron microscopy (EM)
- fluorescence microscopy
(FM) - light microscopy (LM)
Are used in detection of viral proteins and other enzymes. These tests use specific monoclonal or
monospecific antibodies that are raised against specific viral antigens.
Enzyme-Linked Immunosorbent Assay (ELISA)
Direct Immunofluorescence Assay RIA
detection of viral genome
a) DNA probes
b) dot blot or Southern blot analysis
c) Northern blot or RNA:DNA probe hybridization
d) polymerase chain reaction (PCR), and reverse transcriptase PCR (RT PCR):
(1) used in studying the expression of specific viral genomes on the
different cell types;
(2) detecting, in clinical specimens, viral genomes that do not
provide any CPE or for which no serological test are available; and
(3) detecting slowly replicating or nonproductive viruses, such as human papilloma virus or CMV.
DNA probes
It is a DNA amplification system that allows a millionfold amplification of a target sequence
of nucleic acids, at least 100,000-folds in a few hours. Used specifically to detect latent and integrated sequences of viruses, and viruses present in low concentration in n clinical specimens
polymerase chain reaction (PCR), and reverse transcriptase PCR (RT PCR):
- detect specific viral antibodies in serum of the infected host
- it is used to identify the virus and its strain or serotype
- it is used to determine whether viral infection is an acute or chronic infection, or primary infection or reinfection
- it is used for diagnosis of
viral infections that cause diseases of long duration - it is used for diagnosis of infections caused by viruses that are difficult to culture
viral serology
viral serology tests
a) Hemagglutination inhibition (HI) test
b) neutralization test (NT)
c) indirect fluorescent antibody (IFA) test
d) ELISA; RIA; latex agglutination test (LAT); and Western blot
used for detection of viruses
(orthomyxoviruses) that agglutinate red blood cells of chickens, guinea pigs, human, or other mammals
Hemagglutination inhibition (HI) test
based on inhibition of infection by the antibody and that of CPEs of the viruses in tissue culture cells
neutralization test (NT)
from respiratory system
a) Direct examination by EM/IF: nasopharyngeal aspirate
b) Serology: throat swab, throat washing
From central nervous system (CNS)
a) Direct examination by EM/IF: brain biopsy or cerebrospinal fluid (CSF)
b) Serology: feces, blood (for arbovirus), CSF, and brain biopsy
From skin
a) Direct examination by EM/ID: Vesicular/pustular fluid, ulcer scrapings, and
crusts
b) Serology: Macular/papular scrapings, vesicular/pustular fluid, ulcer scrapings, crust, urine
From eye
a) Direct exam by LM/IF: conjunctival scrapings and smears
b) Serology: conjunctival scrapings or swab
From liver
a) Direct examination: serum and feces
b) Serology: blood (yellow fever
From congenital infections
a) Serology: throat swab, products of conception
