Intro to Infectious Disease Diagnosis Flashcards
Tissues and cells stained w/ “general” stains, then observed microscopically for general morphologic features
Histology/cytology
- Tissues = histology
- Cells = cytology
Histology/cytology
- Advantages
- May be quick to perform
- Allows observation of an arry of infectious and other (malignant, necrotic) process
Histology/cytology
- Disadvantages
- Not specific for any infecting organism or disease syndrome (no definitive disease diagnosis)
- Requires considerable expertise to read (usually a pathologist)
Tissues and cells examined w/ an electron microscope
Electron microscopy (EM)
Electron microscopy
- Advantages
- Ultrastructure of organism can be observed
- Good for viruses, etc., that can be diagnosed through other approaches
Electron microscopy
- Disadvantages
- Expensive, requires expertise to perform/read
- Usually no definitive disease diagnosis
Tissues and cells assayed for the presence of unique organismal nucleic acid sequences; routinely involves use of nucleic acid probes and nucleic acid amplification
Molecular diagnostics
Molecular diagnostics
- Give example of a probe and amplification
Probes: Fluorescence in situ Hybridization (FISH)
Amplification: Polymerase Chain Reaction (PCR)
Molecular diagnostics
- Advantages
- Very specific for a single type of organism
- Good for viruses, etc., that cannot be diagnosed through other applications
- Very sensitive when amplification is used
Molecular diagnostics
- Disadvantages
- Expensive
- Cumbersome (but simplified methods are appearing)
- Few FDA-cleared methods (but this is improving)
Cultivation of microorganisms in in vitro systems to allow organism(s) to replicate or grow, so they can be observed and characterized
Isolation in culture
Isolation in culture
- Advantages
- Allows many type of organisms to be detected at the same time
- Not organism specific (an open system)
Isolation in culture
- Disadvantages
- Slow
- Not useful for some organisms (that do NOT proliferate in in vitro systems)
- Organism viability required
Tissues and cells are assayed for the presence of unique organismal Ags
Ag detection
When doing Ag detection, ____ indicates the identity of the Ag in the cells/tissues
Reactivity
Ag detection
- Advantages
- Usually quick
- Provides definitive identification
- Organism viability is not required
Ag detection
- Disadvantages
- Detects small amounts of infecting agent poorly compared to isolation in culture or molecular methods
- Detects only a single (or limited related group of) target Ag(s) at the same time
Indirect evidence of infection through detecting Abs produced against the infecting agent;
- Assays are immunoserologic, involving reacting patients sera w/ known Ags
- Patient’s Abs react w/ their homologous Ag, thus identifying the unknown Ab
Serology/Ab detection
Serology
- Advantages
- Good for detecting infections caused by organisms that are difficult to isolate in culture
- Good for detecting infections caused by unsocial organisms (those that are not vaccinated against or acquired routeinly (ex: HIV)
- Important when species for testing are difficult to collect (i.e., a brain biopsy)
What sample is used when specimens for testing are difficult to collect (brain biopsy)?
Peripheral blood sample
Serology
- Disadvantages
- Sometimes slow
- May require comparison of Ab levels in two samples collected 2 weeks apart
5 reasons that a definitive diagnosis is important for infectious diseases
- Ensure appropriate therapy (eliminate unnecessary therapy)
- Give patient realistic prognosis
- Implement appropriate infection control measures
- Education
- Research
