Holistic Overview of Diagnostic Testing Flashcards
what are 5 important considerations for deciding diagnostic testing?
- what am i looking for/need to measure?
- what sample do I need?
- how do I handle that sample?
- where do i send the sample?
- fill out the correct submission form properly
what are 6 general types of tests?
- molecular for genetic material: PCR/rtPCR, RNA seq
- immunoassays:
-ELISA (tests for antigen or antibody
- serology (antibody titer)
-antigen/antibody
-SNAP tests (for blood or fecal, uses ELISA technology, tests for antigen or antibody); example is equine SNAP foal IgG test to check for immune transfer)
-western blot
-fluorescent antibody
-flow cytometry: detect and measure physical and chemical characteristics of a population of cells or particles
-crossmatching of blood: to determine if blood is compatible with the blood of an intended recipient - chemical/minerals: heavy metals, renal calculi, selenium
- organic compounds: vitamins, toxins, mass spec, chromatography
- live/viable things: virus isolate, bacterial culture and sensitivity
- pathology tests:
-cytology: study of cells
biopsy: sample taken from live animal; incisional, excisional, formalin fixation, fresh material
necropsy/autopsy:
-gross pathology, histopathology, ancillary testing
–look at fresh tissues for bacteriology, PCR, etc.
–look at formalin fixed tissues via hematoxylin and eosin stain
what are considerations to ensure proper sample collection?
- live versus dead: blood versus organ collection
- fluid versus solid
- feed, water, environment (toxin or mineral deficiency)
describe centesis in live animals
- cytocentesis: puncture of bladder to remove urine
- abdominocentesis: surgical puncture to remove fluid from abdominal cavity
- thoracocentesis
- amniocentesis
can examine fluid for protein, biochem parameters, cells, infectious agents, etc.
describe urinalysis components
urine specific gravity-refractometry
blood, protein, glucose, pH, cytology
describe maine coon cat hypertrophic cardiomyopathy
hereditary disease, so use PCR on EDTA refrigerated blood to test for A31P C gene (MYBPC3)
describe copper storage in labrador testing indications
- copper accumulates in the liver causing hepatopathy
- sample: 50mg liver
- collection: biopsy
- sample handling: fresh and/or formalin fixed
describe white muscle disease (nutritional deficiency) testing indications
- due to vitamin E/Se deficiency
- samples:
-selenium:
–use whole blood, serum, plasma
–liver: fixed or fresh, 50mg
-vitamin E: serum, CSF, liver (cold or frozen) - also need to sample feed!! representative sample:
-handful from top, middle, and bottom of a bag of feed or portions of different samples from different lot numbers and batches
-for hay sampling: hay probe/corer and collect from multiple bales - vitamins are heat sensitive! send samples as collected, so do not dry or heat prior to shipment
describe testing for infectious agents
- bacterial (or fungal) culture and sensitivity: fresh tissue needed
- virus isolation: need fresh tissue
- fluorescent antibody testing: fresh tissue
- PCR: fresh or paraffin embedded tissue
- serology: serum or other fluid
- SNAP tests: blood or feces (antigen = presence of agent, antibody only = exposure)
how are samples for aerobic culture and anaerobic culture handled differently? (5)
- anaerobes: usually collected from a warm, moist environment low in oxygen; avoid shocking them by exposing to oxygen or allowing sample to dry!
- refrigeration is not preferred bc can affect viability
- aspirates or biopsy specimen more desirable than swabs (if swab, should be submitted in an anaerobic transport medium
–fluid specimens: if collect by needle aspiration, expel all air from barrel of syringe prior to collection and then transfer contents to a sterile tube with no additives and fill tube completely
–tissue specimens: >2-3cm in diameter, smaller samples placed in anaerobic transport medium - if a tubular organ being removed, can tie off a segment before removal
- sensitivities not routinely carried out
if sampling ruminant fetuses so can’t pull blood, what can you collect? what checking for?
amniotic fluid from forestomach to check for antibodies in fetus to indicate if an in utero infection
describe SNAP testing of canine parvovirus
looking for parvovirus antigen in feces, does not cross react with modified live vaccines
describe testing indications of cows with respiratory disease (multifactorial etiology) (5)
- bacterial culture and sensitivity, but must have a differential list to tell lab what to look for
- PCR: need a differential list! there are panels with multiple virus and bacterial agents, but need a place to start
- virus isolation: need differential list
- fluorescent antibody test: need to ask for specific agents
- serology: need to ask for specific agents
AKA have some idea of what you’re looking for
how do you collect the sample for bacteriology and virology from cows? 3 live samples and 1 dead sample
live:
1. nasopharyngeal swab
2. tracheal wash
3. bronchoalveolar lavage
dead: respiratory tissue
describe testing indications for a 9 month old calf with blackleg
- due to clostridium chauvoei
- submit fresh muscle or heart
- also a fluorescent antibody test; quick and cost efficient (gold standard for rabies)
