Podcast
Questions and Answers
The primary purpose of clinical biochemistry includes monitoring treatment and predicting clinical outcomes of diseases.
The primary purpose of clinical biochemistry includes monitoring treatment and predicting clinical outcomes of diseases.
True
Urine samples are not typically used for biochemical testing.
Urine samples are not typically used for biochemical testing.
False
The black blood collection tube is used for serum biochemistry tests.
The black blood collection tube is used for serum biochemistry tests.
False
Sodium fluoride is used in blood glucose analysis to enhance glycolysis.
Sodium fluoride is used in blood glucose analysis to enhance glycolysis.
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Analytical sensitivity measures how precisely an assay detects a specific substance.
Analytical sensitivity measures how precisely an assay detects a specific substance.
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The reference interval for normal blood glucose concentration is 4.0 - 6.0 mmole/L.
The reference interval for normal blood glucose concentration is 4.0 - 6.0 mmole/L.
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Grey blood collection tubes contain potassium oxalate for glucose testing.
Grey blood collection tubes contain potassium oxalate for glucose testing.
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The light blue blood collection tube is used for serum biochemistry testing.
The light blue blood collection tube is used for serum biochemistry testing.
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The Detection limit refers to the maximum amount of analyte that can be detected in a sample.
The Detection limit refers to the maximum amount of analyte that can be detected in a sample.
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A Levy-Jennings plot can indicate a shift if 6 or more results are consistently on one side of the mean.
A Levy-Jennings plot can indicate a shift if 6 or more results are consistently on one side of the mean.
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Therapeutic Drug Monitoring (TDM) is focused solely on the nutritional needs of patients.
Therapeutic Drug Monitoring (TDM) is focused solely on the nutritional needs of patients.
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Random error can lead to results that are accurate but imprecise.
Random error can lead to results that are accurate but imprecise.
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The Coefficient of Variation (CV) is calculated using the formula CV = (mean/SD) x 100.
The Coefficient of Variation (CV) is calculated using the formula CV = (mean/SD) x 100.
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Systematic error can result in precision but not accuracy.
Systematic error can result in precision but not accuracy.
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Quality control materials are tested weekly in a laboratory setting.
Quality control materials are tested weekly in a laboratory setting.
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External quality control assesses a laboratory's performance by comparing it with that of other labs using different analyzers.
External quality control assesses a laboratory's performance by comparing it with that of other labs using different analyzers.
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Study Notes
Purpose of Clinical Biochemistry
- Diagnosis of disease
- Prognosis - predict the clinical outcome of disease
- Screening for unknown clinical conditions
- Monitoring treatment, progress of chronic conditions, and effectiveness of treatment
Types of Samples for Biochemical Testing
- Blood (serum, plasma)
- Urine
- Faeces
- CSF
- Saliva
- Sweat
- Hair
Blood Collection Tubes
- Red/Yellow: Serum collection, contains clot activator, used for serum biochemistry, drug monitoring, and serum immunology tests.
- Lavender/Black: Whole blood collection, contains EDTA, used for hematology tests and ESR.
- Grey: Plasma collection contains sodium fluoride and potassium oxalate, use for glucose analysis and maintains original glucose and lactate concentrations.
- Light Blue: Plasma collection contains sodium citrate, used for coagulation tests.
- Green: Plasma collection contains lithium heparin, used for emergency biochemistry and plasma biochemistry tests.
Potassium Oxalate Use in Blood Glucose Analysis
- Anticoagulant that binds calcium ions
Sodium Fluoride Use in Blood Glucose Analysis
- Inhibits glycolysis
- Maintains the original glucose and lactate concentrations
Reference Interval for Normal Blood Glucose Concentration
- 4.0 - 6.0 mmole/L
### Spectrophotometric Ways of Measuring Blood Glucose Concentration
- Direct chemical reaction: Glucose reacts with a chemical to get a color change (e.g., dinitrosalicylic acid (DNS)).
- Enzyme-linked reaction: glucose oxidase oxidizes glucose and releases hydrogen peroxide; this reacts with o-Danisidine to give a colored product.
Analytical Sensitivity
- The smallest amount of the analyte that can be detected (detection limit).
Analytical Specificity
- How well an assay detects only a specific substance and does not detect closely related substances.
Accuracy
- How close the result comes to the true value.
Precision
- Reproducibility of multiple measurements.
Limits of Linearity
- A range of concentrations between which the result can be reported as accurate.
Regression Analysis
- Comparison of the output of two different assays, measuring a given analyte in the same samples.
Bland-Altman Plot (aka Difference plot)
- Indicates whether there is agreement between two assays.
Coefficient of Variation (CV) Calculation
- CV = (SD/mean) x 100
Detection Limit (Sensitivity)
- Lowest amount of analyte which can be distinguished from the absence of analyte.
Internal Quality Control
- Are the results today the same as yesterday?
- Quality control materials are manufactured with the analyte in question at various concentrations (H, M, L).
- QC materials are tested on the machine frequently each day, and after changing lamps, reagents, etc.
- Data is plotted on a Levy-Jennings Plot
Levy-Jennings Chart
- Indicates the performance of a test with quality control samples over time.
Levy-Jennings Plot - Trend
- 6 or more points show a consecutive move in the same direction.
Levy-Jennings Plot - Shift
- 6 or more results are on one side of the mean rather than scattered about the mean (i.e., the accuracy of the test has changed, the mean of the values is not the true value).
How Does Random Error Impact Accuracy and Precision?
- Accurate but imprecise (mean value = accurate)
How Does Systemic Error (Positive Bias) Impact Accuracy and Precision?
- Precise but inaccurate
External Quality Control
- Are the results the same as those of other labs performing the same test?
- Quality control samples are regularly sent to all labs.
- Performance Reports are generated.
- Assesses the performance of a lab.
- Compares the performance of the lab with other labs using the same analyzer and method.
- Compares against other analyzers and methods measuring the same analyte.
Precision? Bias?
- How reproducible are the results?
- Systematic difference to the true value.
Point of Care Testing
- Laboratory tests performed at or near a patient and at a site where care or treatment may be provided.
Therapeutic Drug Monitoring (TDM)
- Use of drug measurements in body fluids as an aid to patient management.
Standard Dose
- There is no standard dose because of differences in:
- Absorption rates
- Metabolism rates
- Elimination rates
Causes of Differences in Absorption Rates
- Incorrect timing/method of taking tablets
- GI issues such as Coeliac Disease, Crohn's Disease, etc.
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Description
Explore the essential purposes and sample types used in clinical biochemistry. This quiz covers the importance of biochemical testing in disease diagnosis, prognosis, and monitoring treatment, as well as details on various blood collection tubes and their specific uses. Test your knowledge on a vital aspect of medical diagnostics.
