Exam 5: Quality Assurance in Hematology and Hemostasis Testing

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)?

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?

The following hemoglobin results, reported in g/dL, are obtained on a hospitalized patient on 3 consecutive days: 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 purchased hemoglobin standard is used to adjust a hemoglobinometer. This standard is being used as a:

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 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:

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 anti-deoxyribonucleic acid (DNA) test is positive only in people with SLE but not in all who do. Which of the following is true?

A test that is positive in all patients who have the disease but also in some who do not have the disease is:

What does the CV calculated in Question 2 describe about the white cell counts?

Proper specimen collection and patient satisfaction are components of:

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:

The best way to prevent errors in the laboratory is to ensure:

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?

Which of the following is true regarding reference ranges?

The precision limits of a method are defined by:

Which of the following would most likely be associated with the situation described in Question 11?

The control values for both controls for the prothrombin test were ranging between the mean and $\pm$ 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 laboratory comparing its results to those of other laboratories on the same specimen is an example of:

Which of the following groups of patients should not be included in establishing moving averages using red cell indices?