Book 1: Biomedical Sciences Essential Laboratory Medicine Flashcards
What is clinical chemistry?
The area of pathology with soluble noncellular components analysis of body fluids.
What is an example of a body fluid?
Blood.
What can the soluble noncellular components be?
Small inorganic = salts, ions.
Large organic = lipids, steroids, drugs.
Macromolecules = albumin, enzymes, protein hormones.
What is the aim of the biochemical tests used in a clinical chemistry laboratory?
To accurately quantify the soluble noncellular components of body fluid.
What is it used in the laboratory to reduce variation of measurements?
Standard operating procedures (SOPs).
Quality control testing.
What is examined in clinical chemistry?
Blood serum separately from blood plasma.
Urine.
How is urine get collected for clinical analysis?
24h collection.
In a plastic container with an antibacterial agent from clinic.
What is often collected as urine to be examined clinically?
Early morning urine (EMU).
What are the benefits of collected early morning urine for analysis?
More concentrated.
When is midstream urine (MSU) collected for analysis?
For microbiological purposes.
How are blood samples collected for clinical analysis?
In tubes appropriate to the test required.
What does blood serum contain?
Clotting factors.
Fibrinogen.
Why is blood serum the optimal fluid for blood analysis?
The blood clots in a plain tube –> fibrinogen + clotting factors –> clot –> leave clot factor free –> yellow on top –> blood cells on bottom.
What is the function of centrifugation?
It maximizes the volume of serum.
What can a strong centrifugation cause to the sample?
Lysis of red cells –> release haemoglobin –> red contamination to serum.
How can clotting be prevented?
By the presence of sodium citrate, heparin, EDTA in blood collecting tube.
What is the function of anticoagulant?
It determines which which test can be performed.
What is the function of Heparin?
It blocks clotting irreversibly.
What is the function of EDTA?
Creates ions.
Adds excess of magnesium and calcium.
Enzyme analysis.
What can clotting affect?
Blood glucose measurement.
Adrenaline/catecholamine measurement.
How do hospital collect blood?
Via: Vacutainer tubes = Becton Dickinson (BD).
What is the BD?
A plastic sleeve with a double-ended needle.
How does the BD work to collect blood?
Screwing sleeve-covered-end of needle into holder –> puncturing holder’s vein with other end –> tube pushed down into holder –> blood drawn.
What are creatinine measurements in humans based on analysis?
Constant = healthy humans. Men = 9-18mmol/24h. Women = 7-16mmol/24h.
What is the biggest cause of error in clinical sample analysis?
Incorrect sample labelling.
What must recorded in sample labelling?
Patient’s full name.
Hospital reference numbers.
What can mixing sample labels cause?
Inappropriate treatment.
Patient death.
What can improve sample labelling?
Barcodes.
What are some chemical analysis systems?
Light emission.
Scattering absorption.
Fluorescence.
Luminescence.
How does Flame photometry work as a clinical chemistry analyte?
A spectral scan of portion is produced when metals excite in flame –> lines of emission at wavelengths.
What does the spectral emission produced by the flame photometry do?
It changes the colour of the source flame.
For how many hours and degrees should NaCl and KC be dried before use?
2-3 hours.
100 degrees.
Where must chemicals be allowed to cool before weighing?
At room temperature.
In desiccators.
In container with tight-fitting lid with small air space.
Why is the digital reading for Na adjusted to 140 and K to 50, after aspiration?
To represent them in undiluted serum.
What is a classic example of a simple colorimetric assay in clinical chemistry?
Urea measurement.
What happens in urea measurement?
Urea react with specific compounds –> colour product.
What colour does urea give when it reacts with diacetyl mono-xime under strong acidic conditions?
Yellow.
What happens to the colour produced by glucose colorimetry?
Removed.
Why does the colour product from glucose colorimetry removed?
Colour reaction is a bystander effect of an introduced chromatophore reacting through enzyme.
Metabolic product of glucose acts by a specific glucose degrading enzyme.
What factor makes the yellow product from urea + diacetyl monoxime reaction into red?
Ferricions Thiosemicarbazide.
With what does urea react in analysis by colorimetric assay, under strong acidic conditions?
With diacetyl monoxime.
What does urea give when it reacts with diacetyl monoxime?
A yellow condensation product.
By what is the reaction between urea and diacetyl monoxide boosted?
By ferric ions.
Thiosemicarbazide.
What colour do ferric ions give to the urea reaction with diacetyl monoxime?
Intense red colour.
For how long and in what temperature should we store samples?
No longer than 8 hours.
At room temperature 25-35 degrees.
and
7 days at 2-8 degrees.
Where can we store the samples for longer than 8 hours?
In the freezer.
What shall we do if the samples show evidence of bacterial contamination?
Do not use them for urea estimation.
What else can be used to estimate urea?
Plasma.
When is the colour reagent prepared?
Fresh at the time for analysis.
How is the colour reagent prepared?
By mixing distilled water.
Mixed acid reagent.
Mixed colour reagent.
In ration 1:1:1.
How can we calculate the urea in test sample?
Urea in test sample = (Absorbance of test / Absorbance of Standard) * 150 mg/dl.
What is urea in analytical methods?
One of the most common analytes measured in a laboratory.
What is essential to involve in a urea analysis?
Normal QC pool = internal QC.
What can be obtained from the QC results?
Mean.
Standard deviation.
%CV.
What is the acceptable limit of urea analysis?
4%.
What is the acceptable limit of %CV value of urea analysis?
8%.
What is important for a company that uses QC to do?
Certify their QC materials are traceable to international reference materials.
What are most of the chemicals used in a urea analysis?
Acids.
What should we avoid doing during urea analysis?
Mouth pipetting.
Contact with skin.
What happens in the Glucose analysis by colorimetric assay?
Glucose is presented in plasma –> oxidised by enzyme glucose oxidase (GOD). –> gluconic acid –> leaves hydrogen peroxide free.
What happens to the free hydrogen peroxide?
Converted to water + oxygen, by enzyme peroxidase (POD).
What else happens in the Glucose colorimetric assay?
4 amino phenazone takes oxygen –> + phenol –> pink coloured chromogen, at 515nm.
What is the plasma in the Glucose colorimetric assay?
The specimen of choice for glucose estimation.
For how many hours and at which temperature can plasma glucose levels be stable?
6 hours, at room temperature: 25-35 degrees.
What is it important to happen in blood samples after collection?
Plasma should be separated from the cells.
When should plasma be separated from the cells?
Within an hour after collection.
How much patient’s blood should be collected into an anticoagulant tube?
2 ml.
