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Flashcards in Clinical Biochemistry Deck (21)
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0
Q

What do biochemical tests check for?

A
Urea and creatinine
Glucose
Amylase 
Blood gases 
Sodium, potassium, chloride & bicarbonate 
Total protein and albumin
1
Q

What are the four purposes of running biochemical tests?

A

Screening
Detection of subclinical disease

Monitoring
Monitoring progression or response to treatment

Diagnosis
Confirmation or rejection of clinical diagnosis

Prognosis
Information regarding the likely outcome of disease

2
Q

What do specialised tests check for?

A
Hormones
Specific proteins 
Trace elements 
Vitamins 
Drugs 
Lipids and lipoproteins 
DNA analyses
3
Q

Why are clinical lab procedures automated now?

A

Allows for a high degree of productivity and improves the quality of service.

4
Q

What specimens are used for biochemical analyses?

A
Blood
Urine
Faeces
Cerebrospinal fluid 
Saliva 
Tissue and cells 
Aspirates e.g joint fluid
5
Q

What is the difference between serum and plasma?

A

Plasma has more calcium, chloride and total protein.
Serum has more albumin, aspartate, glucose, potassium, sodium, urea, uric acid.
They both have equal amounts of bilirubin, cholesterol, creatinine.

6
Q

Name a few blood specimen tubes for specific biochemical tests.

A

EDTA with anticoagulant : whole blood analysis, red cell analysis, lipids and lipoproteins.
Lithium heparin with anticoagulant : general
Serum with no anticoagulant : general
Fluoride oxalate : glucose, lactate, alcohol
Trace element : copper, zinc
Heparinised syringe : arterial blood sampling

7
Q

What is the purpose of using a anticoagulant?

A

Blocks the formation of fibrin from fibrinogen. So that blood doesn’t clot. Should not be used if test requires PCR.

8
Q

How does hemolysis occur?

A
In vitro 
Alcohol left on skin 
Use of small needle 
Red cell disorder 
Incorrect storage or transport 
Allows for a high reading of the following in plasma 
Lactate dehydrogenase 
Potassium 
Magnesium
Phosphate
9
Q

What are the sources of error?

A

1) Pre-analytical
2) Analytical
- systemic
- random
3) post-analytical

10
Q

Give four examples of sampling errors.

A

Errors in timing.
Incorrect specimen container.
Incorrect specimen storage.
Insufficient specimen.

11
Q

What is important to note in regards to results?

A

An abnormal result does not always indicate that a disease is present, nor a normal result that is not.

12
Q

Define systemic errors.

A

Error showing a shift in the position of the mean of a set of readings relative to the original mean. It may not obviously affect the distribution of readings about the new mean and so the data would show similar vales for the standard deviation. Such a method is said to show bias towards either the positive (an increase in the mean) or the negative (a decrease in the mean) depending upon the direction of displacement.

13
Q

When do you get a Gaussian distribution?

A

A set of replicate measurements is said to show a normal or Gaussian distribution if it shows a symmetrical distribution about the mean value.

14
Q

Define precision.

A

The precision, or reproducibility of a method is the extent to which a number of replicate measurements of a sample agree with one another and is affected by the random error of the method.

15
Q

Define accuracy.

A

Accuracy is the closeness of the mean of a set of replicate analyses to the true value of the sample.

16
Q

Define sensitivity.

A

The sensitivity of a method is defined as it’s ability to detect small amounts of the test substance.

17
Q

Define specificity.

A

Specificity is the ability to detect only the test substance.

18
Q

Define chelating agent.

A

A substance whose molecules can form several bonds to a single metal ion.

19
Q

What are the chelating agents of blood specimens?

A

Calcium and magnesium.

20
Q

What does plasma contain?

A

Mostly water (91%) with albumin, globulins, fibrinogen, glucose, hormones.