Module 2 Flashcards
Fundamentals in Laboratory Medicine
Occur prior to specimen testing
Pre-analytical Variables
- identification
- age
- sex
- dietary intake
- treatment
- physiological changes
Patient
- type of sample
- type of tube additive
- hemolysis
- contamination
Sample Collection
- storage
- timing
- transportation
- preparation
- centrifugation
- stability
- temperature
Processing
Diagnostic Process that could produce a lot of errors
Pre-analytical Phase
Color of Sodium citrate tube
Blue Cap
Color of Serum tubes
Red or Gold
Color of Heparin tube
Dark Green or Light Green
Color of EDTA tube
Lavender, Pearl, or Pink
Color of Sodium fluoride / Potassium Oxalate
Gray
Sample rejection criteria of the emergency laboratory
- Improper test requests
- Inappropriate transport
- Specimens without barcode
- Improper container
- Misidentification
- Insufficient specimen volume
- Incorrect preservation
- Lipemic specimen
- Hemolyzed specimen
- Clotted samples with fibrin
Diagnostic Process that occurs during actual testing of the specimen
Analytical Variables
Diagnostic Process that occurs after test result is generated
Post-analytical Variables
Post-Analytical Variables
- Wrong entry of test results
- Doctor/Ward Staff not informed about abnormal results in time
- Report signed without confirming result
- Delayed turnaround time
Patient Identification
- The most serious error is failure to properly identify patient
- Two patient identifiers must be present (Name and identification number such as birthday)
Using a needle to take blood from veins
Phlebotomy
If anticoagulant additives are not mixed gently, if blood is drawn from a hematoma, frothing of the sample, venipuncture is incorrect
Hemolysis
Can be caused by prolonged torniquet or long-term IV therapy
Hemoconcentration
The time from receipt of the specimen in the laboratory to the time the result is reported
Turn Around Time
Life or death information that must be directly reported to healthcare provider for immediate action
Critical Value
Quick turnaround time generally an hour or less from specimen receipt until test result reporting
Stat Test
Turnaround time without the immediate need for results
Routine Test
Potential Sources For Interferences
- Hemolysis
- Turbidity
- Lipemia
- Paraproteinemia
- Uremia
- Icterus
- Cross reactivity
Testing occurs in close proximity to the patient
Bedside or point-of-care testing
Most common Point of Care testing errors
- Operational incompetence
- Nonadherence to test procedures
- Use of uncontrolled reagents and equipment
Considered as normal range
Reference Range
Considered as best possible optimal range
Desirable Range
Range of drug concentration that achieves desired effects without causing toxicity
Therapeutic Range
A set of values that includes upper and lower limits of a lab test based on a group of healthy people
Reference range
Quantitative to determine positive and negative test results
Diagnostic Cut-off
The probability that the test result correctly predicts the existence and absence of a particular condition
Accuracy
(true positives + true negatives) / total subjects evaluated
The ability to detect if a disease is really present
Sensitivity
(true positives) / (true positives + false negatives)
The ability to exclude persons who do not have the disease
Specificity
(true negatives) / (true negatives + false positives)
The best screening test must have what?
High sensitivity and followed by confirmatory test with high specificity
Tells you how often a positive test represents a true positive
Positive Predictive Value
(true positives) / (true positives + false positives)
Tells you how often a negative test represents a true negative
Negative Predictive Value
(true negatives) / (true negatives + false negatives)
A statistical measure of the dispersion of data points in a data series around the mean, indicates variability of test results
Coefficient of Variation (CV)
= standard deviation / sample mean
