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
When evaluating an assay for validation, which of the following assesses an assay’s ability to measure the analyte in question in the presence of potentially interfering substances?
a. Specificity
b. Sensitivity
c. Accuracy
d. Precision
Answer: A; Specificity
Whitney, M. S. (2014), Diagnostic Utility of Laboratory Results. VBP 8434 Class Notes. p. 2.
Which of the following is a potential biochemical finding as a result of hemolyzed blood from Shiba and Akita canine breeds of Japan and East Asia:
a. Hypernatremia
b. Hypochloremia
c. Hyperkalemia
d. Hypercholesterolemia
C; Hyperkalemia
Fujise, H., Higa, K., Nakayama, T., Wada, K., Ochiai, H., Tanabe, Y. (1997), Incidence of dogs possessing red blood cells with high K in Japan and East Asia. J Vet Med Sci. 59(6): p. 495. DOI: http://dx.doi.org/10.1292/jvms.59.495
What electrolyte abnormalities are commonly seen when the serum is contaminated with potassium EDTA?
A. ↓ Mg; ↓ Ca; ↑ K B. ↓ Mg; ↑ Ca; ↑ K C. ↓ Mg; ↓ Ca; ↑ Na D. ↓ Mg; ↑ Ca; ↑ Na
A. ↓ Mg; ↓ Ca; ↑ K
(pg. 115; Gilor S and Gilor C. Common Laboratory Artifacts Caused by Inappropriate Sample Collection and Transport: How to Get the Most out of a Sample. 2011. pg 115)
All of the following are affected by a lipemic sample except:
A. Hb B. MCHC C. MCH D. CHMC
D. CHMC
pg 122, & 724. Fundamentals of Veterinary Clinical Pathology 2nd Ed. Stockham & Scott; 2008
Sensitivity of a diagnostic test is defined as:
A. the proportion of patients with the disease that tests negative. B. the proportion of patients with the disease that tests positive. C. the proportion of patients without the disease that tests negative. D. the proportion of patients without the disease that tests positive.
B. the proportion of patients with the disease that tests positive.
(pg. 1031 Schalm’s Veterinary Hematology, 6th ed. Weiss & Wardrop, 2010)
Underfilling of an EDTA tube could cause all of the following, except:
a. False increase in MCV
b. False decrease in HCT
c. Shrinkage of cells
d. False increase in MCHC
a. False increase in MCV
Gilor, Shir and Gilor, Chen. Common Laboratory Artifacts Caused by
Inappropriate Sample Collection and Transport: How to Get the Most out of a
Sample. 2011. Pg. 113.
Contamination of a serum tube with EDTA could cause calcium to ______________ and potassium to _________________.
a. Increase; Increase
b. Increase; Decrease
c. Decrease; Increase
d. Decrease; Decrease
c. Decrease; Increase
Gilor, Shir and Gilor, Chen. Common Laboratory Artifacts Caused by
Inappropriate Sample Collection and Transport: How to Get the Most out of a
Sample. 2011. Pg. 115.
The percentage of patients with a positive test result that actually have the disease is called?
a. Sensitivity
b. Specificity
c. Positive predictive value
d. Negative predictive value
c. Positive predictive value
Diagnostic Utility of Laboratory Results; 2014: pg. 3.
Shultz, Loren. Interpreting Diagnostic Test Results; Slide 33 of presentation.
When a chemistry panel is performed on heparinized plasma rather than on a serum sample, what analyte differences may be seen on the heparinized plasma relative to the serum?
A) Lower albumin, lower potassium, and lower calcium concentrations B) Higher albumin, lower sodium, and higher calcium concentrations C) Higher albumin, lower potassium, and lower calcium concentrations D) Lower albumin, higher sodium, and lower calcium concentrations E) Higher albumin, lower sodium, and lower calcium concentrations
C - Higher albumin, lower potassium, and lower calcium concentrations
Source: Laboratory Artifacts article (Gilor et al.), p. 112
If the results are normally distributed when establishing a reference interval, what percentage of healthy animals will have a result that falls outside of the interval?
A) 3% B) 5% C) 7% D) 10% E) 12%
B - 5%
Source: Diagnostic Utility of Lab Results document (Whitney), p. 1
During quality control of point-of-care analyzers, what is the recommended sensitivity and specificity, respectively, for analytical error detection using the 13s rule?
A) ≥ 95%, ≤ 5% B) ≥ 90%, ≤ 10% C) ≥ 85%, ≤ 5% D) ≥ 80%, ≤ 10% E) ≥ 80%, ≤ 5%
C ≥ 85%, ≤ 5%
Source: ASVCP Guidelines for Quality Assurance document, p. 19
What is the positive predictive value of a new mastitis test in a dairy goat herd with a prevalence of 30%? The test has a reported sensitivity of 90% and specificity of 95%.
a. 28%
b. 46%
c. 89%
d. 96%
c. 89%
PPV = TP/(TP+FP), Sensitivity = TP/(TP+FN), Specificity = TN/(TN+FP), and 30% prevalence = 300 out of 1000; therefore, sensitivity = 0.9 = TP/300 Specificity = 0.95 = TN/700 TP = 0.9*300 TN = 0.95*700 TP = 270 TN = 665
TP = 270 PPV = 270/(270+35) = 89% FN = 30 FP = 35 TN = 665
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. pg. 1031 & 1032
Diagnostic Utility of Laboratory Results Handout, VPB 5578, 2014 as used in V_PBIO 8434, Fall 2014, pg. 2-4
The overall diagnostic accuracy of a test is best assessed by a ______________.
a. Coefficient of Variation
b. Likelihood Ratio
c. Predictive Value
d. Receiver-Operating-Characterisitc Curve
d. Receiver-Operating-Characterisitc Curve
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. pg. 1032
Citrate tubes inhibit the coagulation cascade by binding to _______________.
a. Mg2+
b. Ca2+
c. Tissue Factor
d. Factor VIII
b. Ca2+
Gilor, Shir & Gilor, Chen: Common Laboratory Artifacts Caused by Inappropriate Sample Collection and Transport: How to Get the Most out of a Sample, Topics in Companion Animal Medicine, Vol 26, No 2, 2011, p. 112.
Which of the following represent the single best quality control measure?
a. Daily calibration, measuring system function, electronic system QC sample checks
b. Bi-annual examination audits of lead personnel
c. Bi-weekly measuring of assayed quality control materials and comparison to the QCM manufacturer’s assayed range
d. Bi-weekly measuring of assayed QCM and comparison to the POCA’s analytical performance capability
e. Quarterly participation in an external quality assessment program or comparability testing with the state lab.
D. Bi-weekly measuring of assayed QCM and comparison to the POCA’s analytical performance capability
a) this represents internal QC and should be done in addition to external QC. c) This is QC without tailored statistical control rules (without QC validation) and thus Ped (sensitivity) and Pfr (specificity) is unknown. d) this is statistical QC using tailored control rules (QC validation)
Source: Page 55-56. Harr, K.E. et al, ASVCP Guidelines: Quality Assurance for Point‐of‐Care Testing in Veterinary Medicine. Version 1.0, 2013.
