Question 1

Select the most appropriate action for the results in Question 18.

Accepted Answer

The blood sample should be warmed to 37° C and rerun when a cold agglutinin is present or suspected of being present.The antibody will disassociate from the red cell membrane at this temperature,and the red cells will "unclump." This raises the red count and lowers the MCV,MCH,and MCHC.

Question 2

How do Beckman Coulter and Abbott instruments count red cells and platelets?

Accepted Answer

Instruments manufactured by these companies both use electrical impedance to count and discriminate red blood cells (RBCs)and platelets.

Question 3

Platelet clumps would most likely interfere with which other automated parameter?

Accepted Answer

Large platelet clumps may be counted as WBCs.This results in a falsely decreased platelet count and possibly an increased white cell count.

Question 4

An elevated immature reticulocyte fraction is associated with

Accepted Answer

An elevated immature reticulocyte fraction is associated with a bone marrow response to anemia.It is a reliable indicator of changes in erythropoietic activity and may prove to be a valuable monitoring tool for patients with anemia,such as those with chronic renal failure who are treated with recombinant erythropoietin.

Question 5

Which of the following uses a peroxidase stain channel?

Accepted Answer

The ADVIA 2120 uses a peroxidase channel to help differentiate white cells based on their peroxidase content.

Question 6

Compared with manual methods,automated reticulocyte counting improved which of the following?

Accepted Answer

Automated reticulocyte counting improved all of the listed problems encountered in manual reticulocyte counting.This has resulted in an improvement in precision and accuracy.

Question 7

Which of the following is determined by light transmission between 525 and 555 nm on automated counting instrumentation?

Accepted Answer

Hemoglobin is measured by light transmission between 525 and 555 nm.

Question 8

Counting the number and size of electrical interferences created by blood cells as they pass through a small aperture is a description of which of the following principles?

Accepted Answer

The electronic impedance principle of cell counting is based on the detection and measurement of changes in electrical resistance produced by cells as they pass through a small aperture.

Question 9

All of the following will be invalid when lipemia is present in a blood sample except

Accepted Answer

When a blood sample is lipemic,the hemoglobin is falsely elevated.The MCH and MCHC are also falsely elevated because they use the hemoglobin measurement for their calculation.The MCV is valid because it does not depend on the hemoglobin measurement.

Question 10

An automated hematology analyzer is used to evaluate a blood specimen.Which of the following,coming off the instrument,would require performance of a manual white cell differential as opposed to blood film review?

Accepted Answer

When internal instrument checks fail or cast doubt on the data,the automated differential data are suppressed.This means that a manual differential should be performed.Flagged data may be released after appropriate blood film review,as dictated by the specific laboratory policy.

Question 11

A patient sample comes off an automated cell counter with a failure of the red cell "rule of three." The red count is lower than expected given the hemoglobin.The MCV,MCH,and MCHC are elevated.Which of the following is the most likely reason for this failure?

Accepted Answer

The red count is lower than expected for the data;this suggests a cold agglutinin is present.The red cells are thus clumped at room temperature,and the clumps are being counted as one large cell.This lowers the red count and raises the MCV and MCHC.The only red cell parameter that is probably valid is the hemoglobin measurement.

Question 12

Which of the following is true regarding automated reticulocyte counts?

Accepted Answer

Automated methods use various dyes that bind to RNA and thus allow for counting of reticulocytes by either optical scatter or fluorescence.

Question 13

How do CELL-DYN instruments differentiate red cells and platelets from one another?

Accepted Answer

CELL-DYN instruments use electrical impedance for counting and discriminating red cells and platelets.Pulses between 1 and 35 fL are included in the initial platelet data,whereas pulses greater than 35 fL are counted as red cells.

Question 14

Which of the following is always calculated on cell counters?

Accepted Answer

The MCHC is always a calculated parameter on cell counters.The clinician determines it by dividing the hemoglobin by the hematocrit (which on some instruments is also calculated from the red count and MCV)and multiplying by 100.

Question 15

What is the greatest limitation of automated cell counters?

Accepted Answer

Limitations and interferences may be related to either the methodology or inherent problems in the blood sample.In its literature the manufacturer defines instrument limitations.Some of the method limitations are,in fact,the result of inherent specimen problems.

Question 16

What is the mechanism for the three-part differential found in older Coulter machines or those designed for smaller laboratories?

Accepted Answer

Older Coulter instruments use a special white blood cell (WBC)lysing agent that causes differential shrinkage of white cells,allowing the different white cells to be counted and sized based on their impedance.

Question 17

What does the pneumatic system of cell counters do?

Accepted Answer

The pneumatic system includes the vacuums and pressures required for operating the valves and moving the sample through the hydraulics system.

Question 18

Forward light scatter,when used in an instrument using the optical scatter principle,correlates with cell

Accepted Answer

Forward light scatter correlates with cell volume (size).

Question 19

What technology minimizes the problems of a rigid aperture,including protein buildup,coincidence,and a single cell being counted twice?

Accepted Answer

The use of hydrodynamic focusing avoids pitfalls and potential problems when using a rigid aperture.The outer sheath fluid minimizes protein buildup and plugs,eliminates recirculation of cells,and reduces pulse height irregularity and coincident passage loss.

Question 20

What principle does the Sysmex SE-9000/9500 use to analyze and separate white cell populations?

Accepted Answer

The Sysmex 9000 analyzes WBCs by low-frequency direct current and high-frequency current.A scattergram of radiofrequency detection signals (y-axis)versus direct-current detection signals (x-axis)is plotted and yields separation of the white cells through the application of floating discriminators.

Quiz 15: Automated Blood Cell Analysis