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22 Cards in this Set
- Front
- Back
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Laboratory studies in disease - SOAP |
S - subjective O - objective A - assessment P - plan |
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Precision vs Accuracy |
Precision - the values obtained on repetitive measurements Accuracy - the extent to which measurements approach the "true" value |
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Gaussian Distribution |
Mean - average Median - middle value Mode - value occurring with the greatest frequency Range - difference between highest and lowest value |
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What are causes of biological variability? |
Inter-individual: race, gender, age, body size Intra-individual: circadian rhythms, menstrual cycle, aging, seasonal |
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What are testing phase causes of variability? |
pre-analytic variability, analytic, post-analytic |
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What is the first view for why physicians order tests? |
-to confirm a clinical impression -to rule out a possible diagnosis or disease -to use as a therapeutic or management guide -to use as a prognostic guide -to detect disease |
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What is the second view for why physicians order tests? |
-to diagnose for a disease -to determine the severity of disease -to determine appropriate management of the patient -to monitor therapy -to monitor drug toxicity -to predict response to treatment |
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What are the steps in ordering? |
1.MD writes the order 2.Clerk writes requisition 3.Lab prepares tube 4.Phlebotomist draws the blood 5.Transport to lab 6.Log in specimen 7.Lab separates serum 8.Storage until analysis 9.Prepare worksheets |
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Factors affecting results: Time of lab tests and patient prep |
-8 am
-fasting |
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Venipuncture techniques |
-adequate mixing -sufficent quantity |
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Anticoagulants and their uses in the laboratory |
Red top Lavender top |
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Red Top |
-no additive use: general biochemistry |
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Green Top |
additive: heparin use: general biochem acts as antithrombin preventing formation of thrombin thus preventing fibrin formation (clotting) |
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Lavender Top |
additive: EDTA
use: hematology (preserves cellular constituants of blood) acts by removing calcium ions by chelation but also chelates other ions in the blood |
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Other factors affecting results |
-clotting and exposure of serum to clot -centrifugation -removal of supernatant -storage and transport of specimen -temp -exposure to light -exposure to air -pH |
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Truth Table |
Disease Present Absent Positive True pos False pos Negative False neg True neg |
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Sensitivity |
Frequency of correct result in patient WITH disease (true positive) Sensitivity = TP / (TP + FN) x 100 |
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Specificity |
Frequency of the correct result in a healthy patient (true neg) Specificity = TN / (TN + FP) x 100 |
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Predictive value of a Positive result |
Percent of positive results that are true positives (+) PV = TP / (FP + TP) x 100 |
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Predictive value of a Negative result |
Percent of negative results that are true negatives (-) PV = TN / (TN + FN) x 100 |
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Efficiency |
(TN + TP) / (TN + TP + FN + FP) x 100 |
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Prevalence |
(TP + FN) / (TP + TN + FP + FN) x 100 |
