Clinical Biochemistry Flashcards
What do biochemical tests check for?
Urea and creatinine Glucose Amylase Blood gases Sodium, potassium, chloride & bicarbonate Total protein and albumin
What are the four purposes of running biochemical tests?
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
What do specialised tests check for?
Hormones Specific proteins Trace elements Vitamins Drugs Lipids and lipoproteins DNA analyses
Why are clinical lab procedures automated now?
Allows for a high degree of productivity and improves the quality of service.
What specimens are used for biochemical analyses?
Blood Urine Faeces Cerebrospinal fluid Saliva Tissue and cells Aspirates e.g joint fluid
What is the difference between serum and plasma?
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.
Name a few blood specimen tubes for specific biochemical tests.
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
What is the purpose of using a anticoagulant?
Blocks the formation of fibrin from fibrinogen. So that blood doesn’t clot. Should not be used if test requires PCR.
How does hemolysis occur?
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
What are the sources of error?
1) Pre-analytical
2) Analytical
- systemic
- random
3) post-analytical
Give four examples of sampling errors.
Errors in timing.
Incorrect specimen container.
Incorrect specimen storage.
Insufficient specimen.
What is important to note in regards to results?
An abnormal result does not always indicate that a disease is present, nor a normal result that is not.
Define systemic errors.
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.
When do you get a Gaussian distribution?
A set of replicate measurements is said to show a normal or Gaussian distribution if it shows a symmetrical distribution about the mean value.
Define precision.
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.
