Questions and Answers
What is the primary purpose of biochemical tests in medicine?
What is the primary goal of screening in healthcare?
What is the term used when making a correct decision between diseases presenting a similar clinical picture?
What is an example of a biochemical test used for screening?
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What is the primary purpose of biochemical tests in prognosis?
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What is an example of a biochemical test used for monitoring?
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What type of disease is targeted by screening?
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What is the main category of clinical chemistry tests that includes tests such as Sodium, Potassium, and Chloride?
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What is the term used to describe the doctor's prediction of how a patient's disease will progress?
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What is the purpose of serial measurements of plasma creatinine concentration?
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What type of tests are typically referred to larger laboratories?
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What is the purpose of an urgent test in the emergency lab?
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What is an example of a complication of treatment that biochemical tests can detect?
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What is necessary to monitor the course of an illness?
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What is an example of a specialized test?
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What is the characteristic of subclinical diseases?
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What is the specimen of choice for most blood tests?
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Why is plasma preferred over serum in some cases?
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What is the disadvantage of using plasma?
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When is a skin puncture used to obtain a blood sample?
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What is the difference between plasma and serum?
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Why is serum preferred over plasma in some cases?
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What is the acceptable site for skin puncture in an infant younger than 1 year?
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When is whole blood required for testing?
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What does 'accurate' mean in physical science?
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What is the main difference between accuracy and precision?
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What is the best way to express the degree of precision of a measurement?
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What is the shape of the curve obtained by plotting the values from multiple analysis of a sample?
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What is the purpose of control specimens in laboratory testing?
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What is an example of a situation where a measurement is precise but not accurate?
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What is the term used to describe the proximity of a measurement to the true value?
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What is the term used to describe the repeatability or reproducibility of a measurement?
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What is the effect of EDTA on calcium concentration in blood?
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Why should blood samples not be taken 'downstream' from an intravenous drip?
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What is the effect of long-term storage of blood samples on potassium and phosphate levels?
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What is the main reason for misidentified specimen in laboratory results?
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How does the sex of the patient affect blood hemoglobin concentrations?
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What is the effect of a vegetarian diet on lipid and phospholipid concentrations?
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What is the effect of age on bilirubin levels in infants?
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What is the effect of age on blood glucose concentration in newborns?
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Study Notes
Clinical Chemistry and Biochemical Tests
- Biochemical tests are used extensively in medicine for diagnosis, prognosis, monitoring, and screening.
- The results of biochemical tests are useful to clinicians in making a differential diagnosis, confirming or rejecting a diagnosis, and predicting the course of a disease.
Diagnosis and Prognosis
- Diagnosis is the art of distinguishing one disease from another based on a patient's history and examination findings.
- Biochemical and other investigations are used to distinguish between diseases with similar clinical pictures.
- Tests may be selected to confirm or disprove a diagnosis, and biochemical tests are important for confirming or rejecting a clinical diagnosis.
- Prognosis is a doctor's prediction of how a patient's disease will progress, based on knowledge of the disease's course in other patients and the patient's general health, age, and sex.
- Tests used primarily for diagnosis may also provide prognostic information, such as serial measurements of plasma creatinine concentration in progressive renal disease.
Monitoring and Screening
- Monitoring involves sequential recording of a patient's condition to follow the course of an illness and monitor the effects of treatment.
- Biochemical tests may be used to detect complications of treatment, such as hypokalemia during diuretic treatment.
- Screening involves detecting individuals affected with a condition before it becomes clinically apparent, such as mass screening of newborn babies for phenylketonuria (PKU) and congenital hypothyroidism.
Categories of Clinical Chemistry Tests
- Core biochemistry tests: commonly requested tests of value in many patients, carried out in every biochemistry laboratory (e.g. sodium, potassium, chloride, urea, creatinine, calcium, phosphate, etc.).
- Specialized tests: less commonly asked tests that may be referred to larger laboratories (e.g. DNA analysis).
- Urgent tests: tests processed rapidly in emergency laboratories, such as those needed for immediate treatment decisions.
Specimen Collection and Identification
- Blood may be obtained from veins, arteries, or capillaries, with venous blood being the specimen of choice.
- Skin puncture may be used to obtain a small volume of blood for a blood test, especially in infants.
- Whole blood, plasma, or serum can be used for testing, each requiring specific collection and preparation procedures.
- Specimen identification is critical, with errors in labeling or identification being a common source of erroneous lab results.
Biological Factors Affecting Test Results
- Sex of the patient: e.g. lower blood hemoglobin concentrations in women, affecting serum bilirubin concentrations.
- Age of the patient: e.g. bilirubin levels in infants, low blood glucose concentrations in newborns.
- Diet: e.g. vegetarianism affecting LDL and VLDL concentrations, total lipid and phospholipid concentrations.
- Time of sample collection: e.g. cortisol levels.
- Posture of the patient: e.g. supine vs. sitting or standing, affecting certain test results.
- Medical history, pregnancy, drug history, and smoking can all affect test results.
Accuracy and Precision
- Accuracy refers to the proximity of a measurement to the true value.
- Precision refers to the repeatability or reproducibility of a measurement.
- A measurement can be precise but not accurate due to bias in the test method.
- Control specimens are used to ensure the accuracy and precision of laboratory tests.
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Description
This quiz covers the role of biochemical tests in medicine, including diagnosis, prognosis, and monitoring. Learn how clinicians use test results to make informed decisions.