Important Variables Affecting Interpretation Of Lab Results Flashcards
What are examples of analytical errors
Lab equipment malfunction, failure to detect shifts/drifts in quality control, sample mix up, sample contamination
What are examples of post analytical errors
Errors in validation, transcription error, failure in reporting/interpretation of result, excessive turnaround, delay in acting on results
Define sensitivity in setting of diagnostic testing
Proportion of people who have positive test and the disease divided by people with the disease
Define specificity in setting of diagnostic testing
Proportion of people who have negative test and do not have the disease over people without the disease
Define PPV of a test
Positive predictive value - number of people with a positive test who have the disease divided by the number of people with a positive test
Define NPV of a test
Negative predictive value - number of people with a negative test who do not have disease divided by those with a negative test
How does disease prevalence effect PPV and NPV values of a test
As prevalence increases, PPV increases and NPV decreases
How can normal ranges be determined (hint reference limits and intervals)
Using reference limits - value where it is expected that stated population of patients will have values over or under that value
And reference intervals - space between two reference limits
Eg 95% RI is interval between the RL at 2.5% and RL at 97.5%
What are some examples of sub populations that have different reference limits/intervals
Male versus female
Children versus adults
Ethnicity
Healthy versus unhealthy
What are examples of pre analytical errors
Wrong tests requested, blood sampled from IV lines, delayed separation of components, temperature, wrong tube/incorrectly filled, labeling errors , wrong patient
