Question 1

The precision limits of a method are defined by&#10;A)the mean.&#10;B)the SD.&#10;C)sensitivity.&#10;D)specificity.

Accepted Answer

Evaluating the same specimen multiple times and applying statistics to the results determine precision or reproducibility.The SD describes the precision.The mean is the average result (assuming a gaussian distribution).Sensitivity describes how well a test identifies positive patients,whereas specificity is how well it identifies only positive patients.

Question 2

A clinical laboratory scientist performs 30 replicate hemoglobin determinations on a single blood sample.When statistics are used to determine the precision of the method,the mean is 13.8 g/dL and 1 SD is 0.1 g/dL.This means that 95.5% of the results on this specimen lie

A)between 13.4 and 14.2 g/dL.
B)between 13.6 and 14.0 g/dL.
C)between 13.5 and 14.1 g/dL.
D)between 13.7 and 13.9 g/dL.

between 13.6 and 14.0 g/dL.

Accepted Answer

Because 1 SD is 0.1 g/dL,2 SD = 0.2 g/dL.Thus 95.5% of the results lie between 13.6 (±2 SDs)and 14.0 (+2 SDs).

Question 3

Which of the following groups of patients should not be included in establishing moving averages using red cell indices?&#10;A)chemotherapy patients&#10;B)female patients&#10;C)obstetric patients&#10;D)surgical patients

Accepted Answer

Chemotherapeutic drugs often interfere with DNA metabolism,and this affects the mean cell volume (MCV)and mean cell hemoglobin (MCH),two of the red cell indices used in the moving averages determination.These patients thus should not be used when setting up this method as a quality control tool.It is also true that,when using moving averages as part of a quality control program,an out of control situation often occurs when a group of 20 patients includes primarily oncology patients.

Question 4

One of two controls that have been evaluated over the last 28 days gives a result on day 29 between 2 and 3 SDs of the mean;the other control is within 2 SDs of its mean.What is the correct procedure to follow?

A)Ignore the result unless it happens again the next day.
B)Rerun the control and, if acceptable, continue with patients.
C)Recalibrate the instrument.
D)Open new vials of controls and repeat both controls.

Accepted Answer

One control is acceptable,whereas the other is a warning that the method may be going out of control.The test option in this case is to repeat the analysis of the control,and if it is acceptable,continue with patient analysis,reporting the results.The instrument does not appear to need recalibration because one control is acceptable and the other is within 3 SDs (1 result of 20 can acceptably be within ±3 SDs).If the repeat on the "out of control" vial is still out between 2 and 3 SDs,then a new vial of that control should be opened and analyzed.The control that was acceptable does need to be repeated.

Question 5

Which of the following is true regarding reference ranges?&#10;A)should be derived from reference books&#10;B)need to be determined only for adults&#10;C)can be established by running the test procedure on 10 healthy people&#10;D)are ranges of values for an analyte in normal healthy people

Accepted Answer

Reference ranges should be determined by evaluating a group of perhaps as many as 120 normal healthy people for the same analyte.If the analyte differs in different groups,based on data such as age and sex,it must be determined for each group if at all possible.

Question 6

The antinuclear antibody (ANA)test is positive in almost all people who have systemic lupus erythematosus (SLE).It is also positive in some patients who do not have SLE.The antideoxyribonucleic acid (anti-DNA)test is positive only in people with SLE but not in all who do.Which of the following is true?

A)The ANA test is a good screening test, and anti-DNA test is a good confirmatory test.
B)The anti-DNA test is a good screening test, and the ANA test is a good confirmatory test.
C)Both are good screening tests for SLE.
D)Neither of these tests is valid.

Accepted Answer

Because almost all patients with SLE have a positive ANA test,it is a good screening test (if the result is negative,it practically rules out this diagnosis for a patient).However,because the ANA test is also positive in other patients,the anti-DNA test is a good confirmatory test,because only patients with SLE have a positive result.In practice,the ANA test is done first;if it is positive,then the anti-DNA test is done as follow-up.If a patient is positive with both tests,then his or her diagnosis is SLE.

Question 7

The best way to prevent errors in the laboratory is to&#10;A)purchase high-quality instruments from reputable vendors.&#10;B)hire only well-trained, conscientious workers.&#10;C)have quality management.&#10;D)perform external quality control procedures.

Accepted Answer

Only well-trained,conscientious clinical laboratory personnel can ensure that the best-quality results are routinely obtained for patients.A high-quality instrument is effective only when it is correctly calibrated and maintained.Management,although ultimately responsible,relies on the laboratory personnel to be aware of potential problems in assays.External quality control programs do not guarantee the daily validity of patient results.

Question 8

A laboratory gets numerous complaints regarding the length of time it takes hematology results to get to the emergency department.What would be an appropriate response?&#10;A)Make this a quality assurance project.&#10;B)Ignore the complaints.&#10;C)Explain why it takes so long.&#10;D)Tell the employees to work faster.

Accepted Answer

Quality assurance evaluates the process from the time a test is ordered until it is reported to the correct patient chart.One of the responsibilities a clinical laboratory has is to get results to physicians and other caretakers in a timely manner;the acceptable turnaround time (TAT)for a particular procedure will vary depending on the reason it is ordered.Obviously,an emergency department has a need for rapid TAT.Complaints from caregivers should never be ignored;it probably is not reasonable to tell employees to work faster,and explaining why it takes so long will not help provide good patient care.

Question 9

A purchased hemoglobin standard is used to adjust a hemoglobinometer.This standard is being used as a&#10;A)control&#10;B)precision check&#10;C)delta check&#10;D)calibrator

Accepted Answer

Standards are used to calibrate instruments.Controls are used to routinely evaluate the accuracy of a method once it is calibrated.Precision is a measure of reproducibility,whereas delta checks compare a patient result with a previous result (same test on the same patient).This can only be done for a test result that essentially does not vary significantly from testing time to testing time.

Question 10

A patient specimen is analyzed on an instrument known to be in control from previous assays performed on a calibrated instrument and gives a hemoglobin result of 13.2 g/dL.Two hours later it is evaluated on another instrument that is being evaluated for purchase by the laboratory.The result is 11.8 g/dL.This result,when compared with the first,is

A)acceptable agreement.
B)reportable.
C)precise agreement.
D)inaccurate.

Accepted Answer

This result is inaccurate compared with the first because it is significantly different.Precision is not known,because multiple results are needed to determine precision;in addition,precision must be determined using the same instrument,not between instruments.Because it is not accurate,it cannot be reported.

Question 11

The control values for both controls for the prothrombin test were ranging between the mean and ±1 SD for the first 19 days of use.Starting on day 20,the values for both were consistently between +1 and +2 SDs.This is an example of a

A)shift.
B)trend.
C)random error.
D)predictable error.

Accepted Answer

The answer of The control values for both controls for...

Question 12

A patient's white blood cells (WBCs)are counted on an automated cell counter 10 times.The mean white count is 8000/mL,and the standard deviation (SD)is 300.What is the coefficient of variation (CV)?&#10;A)0.04%&#10;B)2.6%&#10;C)3.8%&#10;D)26%

Accepted Answer

The answer of A patient's white blood cells (WBCs)are counted...

Question 13

The following hemoglobin results,reported in g/dL,are obtained on a hospitalized patient on 3 consecutive days:
$\frac{\text { Day 1 }}{14.3} \quad \frac{\text { Day } 2}{11.5} \quad \frac{\text { Day } 3}{144}$
The SD for this hemoglobin method was calculated in Question 18.A delta check was obtained on day 2.Controls were run as appropriate each day and were all within limits for this procedure.
What is the most probable reason for the day 2 result when compared with those for days 1 and 3?

A)It is within the 95.5% confidence levels for this test.
B)It may represent an error in patient identification.
C)The patient had a major blood loss between days 1 and 2.
D)It is within the 99% confidence levels for this test.

Accepted Answer

The answer of The following hemoglobin results,reported in g/dL,are obtained...

Question 14

Proper specimen collection and patient satisfaction are components of&#10;A)quality control.&#10;B)quality assurance.&#10;C)reliability.&#10;D)precision.

Accepted Answer

The answer of Proper specimen collection and patient satisfaction are...

Question 15

The tubing that brings the lyse reagent to the hemoglobin cuvette on an automated cell counter is pinched and not delivering any reagent.All hemoglobin values are greater than 20 g/dL.This represents what type of error?

A)random
B)imprecision
C)constant systematic
D)proportional systematic

Accepted Answer

The answer of The tubing that brings the lyse reagent...

Question 16

What does the CV calculated in Question 2 describe about the white cell counts?&#10;A)accuracy&#10;B)reliability&#10;C)proper calibration&#10;D)precision

Accepted Answer

The answer of What does the CV calculated in Question...

Question 17

A laboratory comparing its results to those of other laboratories on the same specimen is an example of&#10;A)precision monitoring.&#10;B)internal quality control.&#10;C)external quality control.&#10;D)delta checks.

Accepted Answer

The answer of A laboratory comparing its results to those...

Question 18

Which of the following would most likely be associated with the situation described in Question 11?&#10;A)operator error&#10;B)fading light source&#10;C)miscalibrated instrument&#10;D)starting a new lot number of thromboplastin reagent

Accepted Answer

The answer of Which of the following would most likely...

Question 19

A test that is positive in all patients who have the disease but also in some who do not have the disease is&#10;A)sensitive.&#10;B)specific.&#10;C)precise.&#10;D)reliable.

Accepted Answer

The answer of A test that is positive in all...

Deck 5: Quality Assurance in Hematology and Hemostasis Testing