Introduction and Laboratory Concepts Flashcards
What is the minimum number of patients that is MOST appropriate for reference interval generation? A 120 B 40 C 20 D 10
A. 120 - This would be the MOST ideal
What is the minimum number of patients that is USUALLY accepted in veterinary medicine for reference interval generation? A 120 B 40 C 20 D 10
B. 40 - This is what we follow at the VHC
What is the absolute minimum number of patients that is required to make a true reference interval? A 120 B 40 C 20 D 10
C. 20
What is a confidence interval? (example: 95% CI)
We can be 95% confident that we are measuring will fall into the confidence interval. There is a 5% chance that what we are measuring falls out of the confidence interval due to chance.
If you purchase an instrument that conveniently comes with RIs, how can you validate those RIs for your practice/patient population?
Take 20 animals from your population and compare those results to the standardized RI that come with the equipment.
Which of the following are sources of errors in laboratory test?
a. Lipemia
b. Expired reagents
c. Wrong collection tube
d. Exposure to an inappropriate temperature
e. All of the above
E. All can cause error
After collecting a blood sample on an ambulatory call, the veterinarian puts the sample in the dash of the truck on a July day in Missouri. The sample is left in this location until the end of the day, at which point it is put in the refrigerator and shipped out in the morning. This is an example of which type of sample error:
a. Pre-analytical error
b. Analytical error
c. Post-analytical error
d. Reporting error
A. Pre-analytical error
Which of the following is not considered to be a component of quality control? A. Quality control materials and methods B. Analytical quality specifications C. Statistical quality control rule D. Proportional quality control rules
D?
Which of the following statements is true
a. Falsely increased PCV would occur if the microhematocrit tube is filled with blood taken from the upper portion of the anticoagulant tube.
b. Falsely increased PCV would occur if the microhematocrit tube is filled with blood taken from the lower portion of the anticoagulant tube.
c. Centrifugation at low speeds could result in a decreased PCV because of poor packing of RBCs in the microhematocrit tube.
d. Small clots in the microhematocrit tube can result in a falsely decreased PCV.
b. Falsely increased PCV would occur if the microhematocrit tube is filled with blood taken from the lower portion of the anticoagulant tube.
Reference: Gilor. “Common Laboratory Artifacts Caused by Inappropriate Sample Collection and Transport: How to Get the Most out of a Sample” . Topics in companion Animal Medicine. 26:2(2011). Pg 113
Explanation:
A: Should be “Falsely decreased PCV would occur if the microhematocrit tube is filled with blood taken from the upper portion of the anticoagulant tube”
B: Correct answer
C. Should be: “ Centrifugation at low speeds could result in an increased PCV because of poor packing of RBCs in the microhematocrit tube”
D. Should be: “Small clots in the microhematocrit tube can result in a falsely increased PCV” due to inefficient RBC packing
Which of the following medications result in changes to blood calcium concentrations?
a. Thiazide diuretics b. Furosemide c. Phosphate enemas d. All the above
d. All the above
Reference: Gilor. “Common Laboratory Artifacts Caused by Inappropriate Sample Collection and Transport: How to Get the Most out of a Sample”. Topics in companion Animal Medicine. 26;2 (2011) Pg 115
Explanation:
A: decreased urinary excretion of calcium
B: increased urinary excretion of calcium
C: Increased calcium binding resulting in decreased GI absorption
What information is used to determine the overall diagnostic accuracy of a test?
a. ROC curve
b. Positive predictive value
c. Sensitivity of a test
d. Mann-Whitney U test
a. ROC curve
Reference: Jensen AL and Kjelgaard-Hansen M: Chapter 130: Diagnostic Test Validation, in Schalm’s Veterinary Hematology, 6th Edition, DJ Weiss and KJ Wardrop, eds. Wiley-Blackwell, 2010: pp1032
Explanation:
A: correct answer
B: PPV is the predictive value of a positive test or post test probability of disease following a positive test result
C: Sensitivity is the proportion of patients with a disease that tests positive
D: Used to determine if unpaired observations are statistically different
Which of the following is true regarding quality control materials (QCM)?
a. Some commercially available QCM have an expiration date.
b. QCM do not degrade over time.
c. Use of QCM is the only way to confirm that an analyzer is properly functioning.
d. A minimum of 3 levels (low, normal, and high) of QCM is necessary.
Answer: C Use of QCM is the only way to confirm that an analyzer is properly functioning.
(ACVCP Guidelines Pg. 16)
Quality assurance ____________.
a. Monitor analytical performance of instruments.
b. Is only performed outside of a laboratory.
c. Seeks to minimize all types of laboratory error (pre-analytical, analytical, and post-analytical).
d. Seeks to minimize only pre-analytical error.
Answer: C Seeks to minimize all types of laboratory error (pre-analytical, analytical, and post-analytical).
(ACVCP Guidelines Pg. 2)
Which of the following statements is true regarding point-of-care testing (POCT)?
a. POCT should only be implemented in a private practice setting.
b. POCT may be useful in research and disaster relief situations.
c. POCT always has better quality assurance and quality control than traditional laboratory instruments.
d. POCT always uses higher sample volumes than traditional laboratory instruments.
Answer: B POCT may be useful in research and disaster relief situations.
(ACVCP Guidelines Pg. 10-12)
About external quality control (QC) of point-of-care analyzer, which of the following statements is FALSE?
a. External QC is not required on days when patient samples are not measured.
b. External QC is never required if internal instrument QC functions are used.
c. External QC is recommended when the instrument undergoes maintenance or calibration.
d. External QC is recommended when aberrant patient data is observed.
Answer : b. External QC is never required if internal instrument QC functions are used.
ASVCP Guidelines : Quality Assurance for Point-of-care Testing in Veterinary Medicine, Section 2, p. 15 and 24.
In diagnostic test validation, which of the following is NOT part of the analytical performance assessment:
a. detection limit
b. intra-assay variation
c. inter-assay variation
d. ROC curve
Answer : d ROC curve
Schalm’s Veterinary Hematology, Chapter 130 : Diagnostic test validation, p. 1027-1032.
Hemolysis can be a cause of falsely :
a. decreased hematocrit, increased potassium, and decreased inorganic phosphorus
b. increased MCHC, increased inorganic phosphorus, and increased AST
c. increased PCV, decreased potassium, and increased bilirubin
d. decreased RBC, decreased urea, and decreased bilirubin
Answer : b. increased MCHC, increased inorganic phosphorus, and increased AST
Common Laboratory Artifacts Caused by Inappropriate Sample Collection and Transport : How to Get the Most out of a Sample, by Gilor, p. 114-116.
Which of the following correctly defines desirable total error?
A) The sum of random error and systemic error
B) A set limit for combined imprecision and bias
C) The sum of measured random error and measured systemic error
D) A value indicating how far away the a particular value is from the mean
Correct Answer: A The sum of random error and systemic error
QA: Page 9 of 52
A false decrease in serum total calcium concentration may be attributed to which of the following?
A) Delayed serum separation
B) Storage for greater than 24hrs
C) Hemolysis
D) Sample collection in EDTA
Correct Answer: D Sample collection in EDTA
Topics in Companion Animal Medicine: Page 115
Which of the following is true regarding samples collected in heparin tubes?
A) Heparin is considered a preservative for blood glucose.
B) Advocated in analyzing samples with nucleated red blood cells
C) Can be used for the measurement of D-Dimers
D) Lactate, when measured from samples collected in Heparin tube are stable for 8 hrs.
Correct Answer: B Advocated in analyzing samples with nucleated red blood cells
( Topics in Companion Animal Medicine: Page 112)
In regards to erythrocytes all of the following statements are true EXCEPT:
a. Underfilling of an EDTA tube can lead to an increase in MCV and MCHC
b. Persistent hyponatremia may result in an artifactually decreased hematocrit
c. Lysis of erythrocytes can cause a false increase in MCHC
d. Degeneration of erythrocytes can lead to an increase in MCV
A – Underfilling of an EDTA tube can lead to an increase in MCV and MCHC - causes a decrease in MCV due to cell shrinkage
page 113 Common Laboratory Artifacts Caused by inappropriate Sample Collection and Transport: How to get the most out a Sample
In regards to coagulation panels which of the following is correct
a. Underfilling of the citrate tube may cause decreased PT and aPTT times
b. Lysis of red blood cells will cause shortened PT and aPTT times
c. Hemolysis may lead to an increase in thrombin time
d. A sample transferred from an EDTA tube to a citrate tube will cause a decrease in PT and aPTT
B – Lysis of red blood cells will cause shortened PT and aPTT times
page 117 Common Laboratory Artifacts Caused by inappropriate Sample Collection and Transport: How to get the most out a Sample
The following changes may be seen with preanalysis errors EXCEPT:
a. Glucose decreases by 10% every hour when sample is kept at room temperature
b. Bilirubin can be degraded by sunlight up to 50% per hour
c. Bile acids can be falsely elevated by hemolysis
d. Angiotensin-converting enzyme inhibitors may cause potassium to be decreased
D – Angiotensin-converting enzyme inhibitors may cause potassium to be decreased - causes hyperkalemia due to development of hypoaldosteronism
pg 115 Common Laboratory Artifacts Caused by inappropriate Sample Collection and Transport: How to get the most out a Sample
Hemolysis is visualized when the concentration of hemoglobin exceeds this level:
a. 0.02 mg/dL
b. 0.20 mg/dL
c. 2.00 mg/dL
d. 20.0 mg/dL
Answer: D 20.0 mg/dL
Gilor, S., Gilor, C. (2011), Common Laboratory Artifacts Caused by Inappropriate Sample Collection and Transport: How to Get the Most Out of a Sample. Topics in Companion Animal Medicine. 26(2): p. 110. DOI: 10.1053/j.tcam.2011.02.003