Term
What is an analyte?
Give 3 examples |
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Definition
| An analyte is a substance or chemical component that is of interest in an analtyical prodcedure. E.g. biomarkers (biological molecules), Chemical (chemical molecules) and Microorganisms. |
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Term
What are the two most common biological fluids analysed for analytes? |
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Definition
Blood plasma and urine
Plasma= liquid components of blood that carriers the blood cells |
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Term
| What can clinical laboratory testing be used for? |
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Definition
| Diganosis of a disease, monitoring (a patient's response to treatment of drug levels in their bloodstream), Screening (evaluating people's disease risks) and Research. |
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Term
| Define the term True Positive |
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Definition
| True positive is when a patient tests positive for a disease and they have the disease |
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Term
| Define the term false positive |
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Definition
| When the patient does not have the disease but the test is positive for disease in the individual |
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Term
| Define the term True Negative |
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Definition
| When the patient does not have the disease and they test negative for the disease |
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Term
Define the term False negative
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Definition
| When the patient does have the disease but the test is negative |
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Term
| When is it dersirable to have a test that has high sensitivty? |
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Definition
| High sensitivtiy will determine the true positive rate, this would indentifiy all the indivudals with the disease. Therefore high sensitivity is required in screening or in a treatable disease e.g. prostate cancer |
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Term
| When is it dersiable to have a test with high specificitiy? |
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Definition
| High specificity tests would not give a positive result for anyone without the disease. This is ideal for when you want to decrease further investigations, and more diseases which need to be detected early, as early treatment improves prognosis. e.g. Aids and cervical cancer |
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Term
What approach should be undertaken to ensure that only, and all, patients with
the disease test positive for the disease? |
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Definition
| First do a highly sensitive, and all those patients who test positive then do a highly speicifc test to eliminate those that do not actullay have the disease |
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Term
| What factors other than disease can affect labratory results? |
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Definition
| Pre-analytic factors (sampling and handling), Analytic factors (random variations in testing system and sytematic errors) and Post-analytic factors (storage and transportation of samples) |
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Term
| What is meant by contorllable and non-controllable sources of variation? |
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Definition
| Controllable sources of variation are things we can control for via protocol and standardised testing. Non-controllable sources of variation are things we cannot control e.g. Biological variation like age and sex. |
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Term
| List up to ten sources on controllable variation and breifly describe how they influence lab test results? |
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Definition
| Type of blood- e.g. blood taken from venous/arterial system and how it is taken, Posture (lying down and standing up), Sample storage and handling- temperature, light, air etc, sample additives-additives to paritcular analtyes added incorrectly, Stimulats, exercise, diet and starvation, hemolysis |
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Term
| List three categories of non-controllable sources of variation |
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Definition
Biological variation (age, sex)
Behavourial Variation (diet, exercise, stress)
Clinical variation (pregnancy, co-illness, therapteutic drugs) |
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Term
| List up to five sources of biological variation and briefly explain how they can impact on lab results |
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Definition
age, sex, cylical, random, ethnicity
analtyes can vary depending on these factors, e.g. different trends. Different ethnicities will have different vitamin D levels depending on time of year (cyclical) |
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Term
| List 3 examples of clinical and behavioural variaiton |
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Definition
Behavioural- exerciese, diet, stress
Cliincal- pregnancy, co-illness, therpaeutic drugs |
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Term
| What is a reference range and what is it used for? |
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Definition
| A reference range is range of 'normal' values of analytes in a healthy population. It is used compare lab results to help establish whether a patient has disease or needs further testing |
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Term
| What is a RCV and what is it used for? |
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Definition
| RCV= Refernce change value, and it is used to to calculate the change in analyte due to normal variation, anything beyond this would be considered signficant and may indicate signs of disease. |
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Term
How is a refernece range estabilshed and what type of distribution does it normally display?
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Definition
| A reference range is estabilhsed by taking the analyte concentrations from a population of healhty people and plotting this, the reference range is the range of analyte concentrations that 95% of the healthy population lies within.. usually a perfectly symmeterical bell shaped distrbituion |
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Term
| How can a reference range be used in disease diagnosis? |
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Definition
| is the patient's analyte concentration is not within the reference range this may be indicative of disease but COMPLEMENTS phsyical exam by a doctor or may suggest that further testing occurs |
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Term
| List up to four important factors that need to be considered when estabilishing a reference range and explain why it is important to take these factors into account |
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Definition
| The effect of age: some analytes differ in age groups, the effect of sex: some analytes differ between genders, The effect of cylical patterns: analytes vary with biological rhythyms in females, and effect of race/ethnicity on refernce range: analytes can differ in different races. Need to match these factors when comparing a refernce range |
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Term
| Briefly discuss how the distribution of a reference range may be affected due to limiations of population based refernece ranges |
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Definition
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