Random Flashcards
What are BJPs
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Bence Jones proteins are abnormal proteins found in the urine of some individuals with certain types of plasma cell disorders, particularly multiple myeloma.
Bence Jones proteins are monoclonal immunoglobulin light chains, which are components of antibodies produced by plasma cells.
Normally, antibodies are made up of two types of protein chains: heavy chains and light chains. In the case of Bence Jones proteins, there is an overproduction of monoclonal light chains that are not being incorporated into complete antibodies.
Coefficient of variation
Standard deviation/mean x 100
This is used to assess the precision or relative imprecision of a measurement.
Generally, a CV below 10% is considered low, indicating good precision and reproducibility. A CV between 10% and 20% is considered moderate, while a CV above 20% is considered high and may indicate poor precision.
The CV can be used to compare the precision of different measurement methods or instruments
Post analytical variation
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Data Entry and Transcription Errors - Typos, misinterpretation of handwriting, or incorrect mapping of results to the corresponding patient can lead to erroneous data and subsequent incorrect interpretation
Reporting and Communication: incorrect identification of patients, mislabeling of results, or failure to deliver results to the appropriate healthcare professionals in a timely manner
Reference range: Variations in reference ranges due to population differences, age, sex, or methodology changes can influence the classification of results as normal or abnormal.
Result interpretation: Errors can occur when results are interpreted in isolation without considering relevant clinical information, leading to incorrect diagnoses or inappropriate treatment decisions.
Imprecision
The degree of random variation or inconsistency in the measurement of a particular analyte or substance.
It is a measure of how closely repeated measurements of the same sample would agree with each other.
Imprecision is assessed by performing replicate measurements of the same sample and calculating the standard deviation or coefficient of variation (CV) of the results.
The CV represents the relative variation as a percentage of the mean value and is often used as a measure of imprecision.
A smaller CV indicates greater precision and less random variation
Control intervals
Control intervals, also known as reference intervals or reference ranges establish a range of values within which the results of a particular test are considered normal for a healthy population.
Control intervals provide a basis for comparing individual patient test results and determining whether they fall within the expected range or deviate from it, potentially indicating a medical condition.
Determining Control Intervals: Control intervals are established through the analysis of samples from a reference population of healthy individuals. These individuals are typically selected based on specific criteria, such as age, sex, and any known medical conditions. The samples collected from this population are analyzed to determine the range of values that are considered normal for a specific laboratory test.
Control intervals are specific to each laboratory test and are expressed in appropriate units of measurement
control intervals are established based on a healthy reference population and may not account for individual variations, such as age, sex, ethnicity, or specific medical conditions
What are serum indeces
Serum indices refer to a set of laboratory measurements that provide information about the quality and integrity of a blood serum sample. These indices are used to assess whether a serum sample meets certain criteria for accurate and reliable test results.
Hemolysis Index: Hemolysis refers to the rupture or breakdown of red blood cells, leading to the release of hemoglobin into the serum. The hemolysis index assesses the degree of hemolysis in a serum sample and is typically reported as a numerical value or categorized as minimal, mild, moderate, or severe. Hemolyzed samples may yield inaccurate results for various analytes, such as potassium, lactate dehydrogenase (LDH), and certain enzymes.
Icterus Index: Icterus refers to the presence of increased bilirubin levels in the serum, which can result from liver diseases or other conditions affecting bilirubin metabolism. The icterus index indicates the degree of bilirubin interference in the sample and is reported as a numerical value or categorized as none, minimal, mild, moderate, or severe. Highly icteric samples may affect the accuracy of certain tests, such as measurement of direct bilirubin and certain enzymes.
Lipemia Index: Lipemia refers to the presence of increased lipid (fat) levels in the serum, leading to turbidity or a milky appearance of the sample. The lipemia index reflects the degree of lipemic interference and is reported as a numerical value or categorized as none, minimal, mild, moderate, or severe. Lipemic samples can interfere with various laboratory tests, including measurement of triglycerides, certain enzymes, and some analytes that rely on spectrophotometric methods.
psuedohyperkalemia
The artifactual elevation of potassium in serum but not in plasma.
This is elevated potassium due to pre-analytical factors that don’t truly reflect the patient’s electrolyte status.
It is important to distinguish between pseudohyperkaleme and true hyperkalemia as true hyperkalemia can quickly lead to fatal cardiac arrythmias, muscle weakness or paralysis.
One of the most common causes of pseudhyperkalemia is the haemolysis of red blood cells during collection.
If this haemolysis is detected than the results will just be suspended and the blood re-taken.
Leukocytosis, thrombocytosis, temperature storage, collection and possibly pressurised centrifugal forces can cause pseudohyperkalemia.
Significant leukocytosis can be seen in numerous diseases such as CLL.
CLL causes increased cellular fragility.
Heparin has also been associated with increased fragility of WBCs.
Thrombocytosis has been reported alongside elevated potassium post splenectomy.
Both increased production of platelets or decreased removal can result in large potassium elevations.
During clot formation fragile platelets may lyse releasing potassium.
Decreased temperature inhibits Na/K ATPase pumps present on red blood cells which results in leakage of potassium outside the cells.
Centrifugal forces and pneumatic tube system transport has been documented as factors that may result in psuedohyperkalemia in the absence of red blood cell haemolysis
Bicarbonate
The bicarbonate ion, HCO3- acts as a buffer for blood.
The kidney’s excrete H+ and reabsorbs bicarbonate ions to regulate blood pH.
If extracellular fluid become acidic, kidneys excrete H+ and conserve bicarbonate.
The bicarbonate ion is the chemical species that comprises almost all the CO2 produced by the body.
These ions are completely filtered by the glomeruli with approximately 90% reabsorption in the proximal tubule and a further 10% in the distal tubule.
The threshold for this system is approximately 26 mmol/L; at concentrations above this level bicarbonate is excreted in the urine.
Increased bicarbonate concentrations in serum can be caused by metabolic alkalosis or in compensated respiratory acidosis.
Decreased serum bicarbonate may indicate metabolic acidosis or compensated respiratory alkalosis.
Mechanism of blood pH control
The kidney’s excrete H+ and reabsorbs bicarbonate ions to regulate blood pH.
If extracellular fluid become acidic, kidneys excrete H+ and conserve bicarbonate.
If blood become too alkalinic, kidneys remove HCO3 and conserve H+.
The kidney and lungs balance the levels of bicarbonate in the body.
So if bicarbonate levels are too high or low, it might indicate that there’s a problem with those organs.
The threshold for this system is approximately 26 mmol/L; at concentrations above this level bicarbonate is excreted in the urine.
Increased bicarbonate concentrations in serum can be caused by metabolic alkalosis or in compensated respiratory acidosis.
Decreased serum bicarbonate may indicate metabolic acidosis or compensated respiratory alkalosis.
Ideal cardiac biomarker
Absolute cardiac specificity -> the marker should be specific to cardiac tissue or to cardiac function i.e. it should not be present in other tissues. This ensures that any changes in the biomarker levels can be attributed directly to cardiac damage
High tissue sensitivity -> biomarker should be sensitive enough to detect even small changes in cardiac health. It should also be able to reflect the severity and extent of damage
Infarct sizing -> measurement of cardiac biomarkers in blood stream should allows us to size an infarct, an infarct is a measure of how much tissue has been damaged by a heart attack
Early release -> cardiac biomarker should be released soon after damage
Specific for irreversible injury -> cardiac biomarker should only be released when there is irreversible injury i.e. ischemia and not just wear and tear
Predictable clearance -> should be able to predict how long the biomarker will be found in the body i.e. how long will it take to be cleared and how is this done.
Measurable by conventional methods -> needs to be easily measured, how quickly can it be measured, are there any dangerous reagents used etc
Cost effective – should be affordable, easily accessible and cost-effective to ensure practicality and widespread utilisation
Evidence – use of the biomarker should have a strong scientific foundation and should be extensively researches, clinical studies etc
How is bilirubin formed
Haem broken down into biliverdin by haem oxygenase
Biliverdin broken down into bilirubin by biliverdin oxidase
How is bilirubin measured
the Diazo method which is a chemical method used to determine bilirubin concentration spectrophotometrically. Diazotised sulfanic acid + bilirubin -> two azodipyrroles which produces a reddish-purple colour at neutral pH and a blue colour at low/high pH. This measures the conjugated/direct bilirubin. An accelerant can be added to the reaction to measure total bilirubin. Unconjugated bilirubin is determined by the total bilirubin-conjugated bilirubin
what is eGFR
Glomerular Filtration Rate is the volume of filtrate produced by both kidneys each minute. It’s approximately 180L/day.
What is creatinine clearance
Creatinine clearance involves the subject collecting all their urine produced over 24 hours into a container, a portion of urine is used to measure the creatinine concentration (Ucreat). A blood sample is also taken during the same 24 hours to determine the plasma creatine (Pcreat).
Cholesterol assays
CHOD-PAP
Amplex red
Lieberman-Burchard
