Diagnostics Flashcards
What is a ESR test?
Eosinophil sedimentation rate
What is a CRP test?
C-reactive protein
What anticoagulant is found in a red top tube?
none
What anticoagulant is found in a yellow top tube?
Gel to speed up clotting
What anticoagulant is found in a purple top tube?
Potassium EDTA
Haematology
What anticoagulant is found in a grey top tube?
Fluoride oxalate
poison
What colour tube would be used to measure U&E?
Serum in a yellow/red topped tube
What colour tube would be used to measure glucose?
Plasma in grey topped tube
What does HBA1c measure?
It is a long term control which shows damage to cells
if you are diabetic and have not complied with treatment until the day before your hospital appointment
What colour tube would be used to measure TFT? (thyroid function)
Serum in a yellow/red topped tube
What colour tube would be used to measure LFT?
Yellow/red topped tube
What is the difference between serum and plasma?
Serum is the yellow fluid produced when blood clots and you centrifuge it. All the clotting factors have been used up
Plasma is prior to clotting and still has clotting factors
Why is a blue tube used to measure clotting factors?
Has citrate which is an anticoagulant, stops red cells using calcium
Used to test clotting factors by adding calcium and measuring clotting time
What is added to a grey topped tube? What does this do?
Fluoride oxalate
It prevents the red cells from using glucose which they would otherwise consume, skewing the results
What enzymes are measured in a liver function test?
1) alkaline phosphatase
2) aspartate amino-transferase (AST)
3) alanine amino-transferase (ALT)
4) gamma glutamyl transferase (GGT)
What hormones are commonly measured in a hormone assay?
Thyroxine
TSH
Cortisol
Low sodium and high potassium electrolyte results indicate what?
Adrenal failure (or haemolysis due to difficult venepuncture)
What happens to urea and creatinine results in renal failure?
The rise
If a patient has high urea and low creatinine what would cause this?
Dehydration
What causes increased liver enzymes? Why?
Enzymes leak into the blood in liver disease.
Renal damage would show what urea and creatinine results?
Both would be high
What cardiac enzymes are measured?
Troponins
Creatine kinase (CK)
Aspartate amino transferse (AST)
Lactate dehydrogenase (LDH)
When do the cardiac enzymes rise following a heart attack?
CK- 4 hours
AST- the next day
LDH- 2 days later
What are the diagnostic methods for detecting a virus?
- Cell culture
- Electron micropscopy
- Antibody detection
serology- ELISA/EIA - Antigen detection
immunoflorescence- IF
enzyme immunoassay- EIA - Genome detection
PCR - Quantification of antibody or antigens
- Serotyping
- Quanitifcation of genomes- “viral load”
- Genome sequencing
What is sensitivity?
The test’s ability to correctly identify positive samples
What is specificity?
The test’s ability to correctly identify negative samples
What is serology? What is it tested on?
The detection of specific antibody or antigen in blood, CSF or saliva
What type of virology testing it conducted on throat swabs, nasopharyngeal aspirate, bronchoalveolar lavage and ET secretions?
IF or PCR
What type of virology testing it conducted on stool samples?
ELISA or PCR
What type of virology testing it conducted on urine samples?
PCR
What type of virology testing it conducted on clotted blood?
Serology (antibody detection
What type of virology testing it conducted on CSF?
PCR
What type of virology testing it conducted on blood (EDTA)?
PCR
Viral load testing
What type of virology testing it conducted on saliva?
Serology and or PCR
What antibody type is a marker for recent or acute infection?
IgM
What antibody is a marker for infection of immunisation in the past without the presence of IgM?
IgG
Viral isolation in cell culture is still needed for what condition?
Herpes simplex virus
How do you diagnose a respiratory virus?
PCR
What kind of sample is required for a respiratory virus?
- Throat swab +/- nose swab
- Nasopharyngeal swab
- Nasopharyngeal aspirate (NPA)
- Bronchoalveolar lavage (BAL)
- Endotracheal tube (ET) secretions
What samples are needed to diagnose a CNS disease, and for which test? (meningitis/encephalitis)
- CSF for PCR
- Stools and throat swab for PCR
- Blood for serology
What test is performed on a stool or vomit sample?
PCR
What are the common bacteriology diagnostic techniques?
1) Culture
- Sterile sites
- Non-sterile sites
2) Serology
3) Molecular techniques
4) Antimicrobial susceptibility testing
How do blood cultures display a positive result?
The bottom of the sample pot reacts with byproducts from bacterial growth causing a visible change in the colour of the pot