Lab Test Stewardship Flashcards
read Pharmacy Practice Standards
& Laboratory Tests
HPA (Schedule 19, Section 3(1))
“In their practice, pharmacists promote health and prevent and treat diseases, dysfunction and
disorders through proper drug therapy and non-drug decisions.”
ACP
Standard 3: Pharmacists must consider appropriate information from each patient. (eg. renal fxn test to adjust dose)
3.5 Information that may be required under Standard 3.4(j) includes:
e) laboratory values
Standard 6: Dispensing a Schedule 1 drug pursuant to a prescription
Standard 13:Prescribing in an emergency
Standard 14:Prescribing at initial access or to manage ongoing therapy
read ACP standard on POCT
“When an interaction with a patient or consideration of patientspecific information indicates that a pharmacist should review laboratory data, and the data is not available, the pharmacist must order the appropriate test, refer the patient to an appropriate regulated health professional to evaluate the need that a test be
ordered, or if appropriate, conduct a Point of Care Test (POCT)
what do you need to order a lab test (3)
– Edmonton Zone (DynaLIFE Medical Labs)
– Calgary Zone (Calgary Laboratory Services)
– North, Central, and South Zones (AHS Laboratory Services)
– Practitioner ID to register with the laboratory, Need practiicioner ID to prove you are a regulated HCP
– Be familiar with the standards and responsibilities*
– A plan for receiving and interpreting the results
• 24/7 contact information (critical results will be phoned to the ordering practitioner), need to contact the person who ordered it ASAP
what are some issues with ordering lab tests
- 30% of laboratory tests in Canada are repeated inappropriately
- T4 and TSH, don’t need to do both
Logistical issues for the patient
– Fasting or dietary restrictions
– Transportation
• Collected sample (e.g., 24 hour urine collection for creatinine clearance)
• To the laboratory (vehicle, parking, scheduling collection, etc)
Specimen Collection for a Laboratory Test
what fluids are mose commonly used for analysis?
- Blood and urine are the most common body fluids used for analysis
- The amount of specimen required, storage container, and timing of collection will depend on the type of laboratory test
– Creatinine clearance*
• Urine 24 hour collection (container)
• Blood 5 mL tube used for estimation
Why Order a Laboratory Test? (4)
- Ensure the drug and dose are appropriate for the patient
– Therapeutic drug monitoring
– Interpreting culture and sensitivity to confirm the correct antibiotic is used - Monitor the patient’s response to therapy
– Does the white blood cell count decrease in response to an antibiotic
– Is the blood glucose responding to addition of a new antihyperglycemic drug
– Is the thyroid responding to a change in dose - Monitor for adverse effects and ensure the patient’s safety
– What is the patient’s renal function
– Does serum creatinine change significantly when a drug known to affect the kidneys (e.g., NSAID, ACE
inhibitor) is added - Screening of patients with preliminary indicators for untreated diseases
– Diabetes risk
– Confirm a suspected illness (e.g., strep throat)
at what point of pt care process do lab tests occur?
any point of pt care process
Assessment, if they’re reaching their goals, implemeting or f/u
Accuracy vs precision
• Accuracy – how close is the test value to the ‘true’ value
– Influence of both random and systematic error
• Precision – how close are the values if the test is repeated
both properties monitored and reported by the
laboratories
• If we assume the test result is an accurate and precise description of what is happening in the patient, the next step is to interpret what the test result means
what does positive test? negative test?
– Positive: suggests disease is present
– Negative: suggests disease is absent
define Sensitivity
- if a test has high sensitivity, what does it mean?
- low possibility of a ________
Ability of the test to correctly identify individuals who have a given condition
– If a test has high sensitivity…
• We can be quite confident that someone with a positive result has the condition we are looking for
• Low possibility of a false negative
⟹ negative result can be used to rule out the condition (SnOUT)
– If a test has low sensitivity…
• A positive result could lead to over treatment
define Specificity
- if a test has high Specificity, what does it mean?
- low possibility of a ________
• Ability of the test to correctly identify individuals who do not have a given condition
– If a test has high specificity…
• We can be quite confident that someone with a negative result does not have the condition we are looking for
• Low possibility of a false positive
⟹ positive result can be used to rule in the condition (SpIN)
– If a test has low specificity…
• A negative result could miss identifying the condition
see slides for equations on calculating sensitivity and specificity
ok
Sensitivity = True Positive/Patients with Disease
Specificity = True Negative/Patients without Disease
Predictive Values
Considers prevalence of condition in the population,
sensitivity, and specificity
what is Positive Predictive Value (PPV)?
Negative Predictive Value (NPV)?
PPV = % of Positive results that are Truly Positive NPV = Negative results that are Truly Negative
PPV = true pos/all positive tests NPV = true neg/all neg tests
Reference Range
- contains ___% of the values
Range of values obtained from testing a large sample of ‘healthy’
individuals
– Plot the distribution of values
• The reference range will contain 95% of the values
- The lower and upper limits are not absolute, but reflect a threshold beyond which the benefits of a therapeutic intervention increase
T/F: the Reference Range may vary from laboratory to
laboratory
True
