Question 1

What causes the RBCs to settle faster through the plasma when inflammation or infection is present?

Accepted Answer

When the red cell mass increases,the red cells fall faster through plasma,thus elevating the ESR;rouleaux formation increases the red cell mass.Rouleaux formation occurs when the net negative charge that normally separates red cells from one another is disrupted by acute phase reactant proteins.RBC agglutination also elevates the ESR.

Question 2

A manual WBC count is performed using a system that makes a 1:20 dilution of blood.When the cells in the four large corner mm² of the hemocytometer are counted,the following numbers of cells are obtained: 8,12,9,and 11.What would be the next step?

Accepted Answer

This white count appears to be very low,in the neighborhood of 2.0 × 10⁹/L [(8 + 12 + 9 + 11)× 20/0.4].To make the cell count more accurate,the number of cells counted must be increased.This can be done by counting the cells in all 9 mm² of the hemocytometer.

Question 3

Which of the following is a good use of the erythrocyte sedimentation rate (ESR)?

Accepted Answer

The ESR is elevated in patients with rheumatoid arthritis.It decreases when the disease is in remission and increases when it exacerbates;therefore,it is useful for monitoring this disease.It is normal in the first 24 hours of acute appendicitis,so is not useful in diagnosis.It is elevated in multiple myeloma,but also in many other clinical conditions,so it is not diagnostic for it.It is normal in osteoarthritis and thus of no value for monitoring those patients.

Question 4

Which of the following can cause a falsely increased ESR?

Accepted Answer

The ESR tube must be kept at the absolute perpendicular to obtain a valid ESR result.Even only a slight tilt of the pipette (tube)causes the ESR to increase.

Question 5

How do sickle cells or spherocytes interfere with the ESR?

Accepted Answer

Abnormally shaped red cells such as sickle cells or spherocytes interfere with rouleaux formation,so they falsely decrease the ESR result.

Question 6

A manual hemoglobin is determined on a patient,and the dilution still appears turbid after letting it sit for 15 minutes.The stained blood film is examined,and sickle cells are observed on the blood film.Equal volumes of the diluted hemoglobin sample and water are mixed together,and the absorbance of this read on a spectrophotometer.How should the hemoglobin result be determined from the standard calibrated graph?

Accepted Answer

Red cells that contain Hb S (sickle hemoglobin)are resistant to lysis in some cyanmethemoglobin reagents.When this occurs,the cyanmethemoglobin dilution should be mixed with an equal part of water,and the optical density (percent transmission)read.This optical density reading is read from the calibration graph to obtain the hemoglobin result.However,because the diluted specimen was diluted 1:2 by water,this result must be multiplied by 2 to obtain the patient's result.

Question 7

Which regulatory standards mandate the concept of "test site neutrality" for all laboratory procedures?

Accepted Answer

The Clinical Laboratory Improvement Amendments (CLIA)require test site neutrality,which means that all testing sites must follow the same regulatory requirements based on the complexity of the test method.OSHA sets standards for safety in the workplace.Joint Commissions and CAP are accrediting agencies.

Question 8

On a standard reticulocyte preparation with new methylene blue,100 of 1000 cells that are counted contain blue-stained granulofilamentous material.The red blood count is 3.22 × 10¹²/L,and the hematocrit is 30%.Calculate the reticulocyte production index (RPI).

Accepted Answer

The RPI uses the corrected reticulocyte count (calculated in Question 25).It then takes into account,based on the patient's hematocrit,the early release of RBCs from the marrow so that when the reticulocytes are counted,it is not just those released in the last 24 hours (1 day)but a piling up of those released over a longer period of time.For a hematocrit of 30%,the average length of time a reticulocyte spends in the blood is 2.0 days.Thus the corrected reticulocyte count of 6.7 is divided by 2 = 3.4.

Question 9

A 1:20 dilution of blood is made for a white count,and the following number of cells counted in the four large corner mm² of the hemocytometer: 12,28,18,and 15.What should be done next?

Accepted Answer

The distribution of cells in these four mm² is unacceptable (exceeds 10 cells);this is not random distribution.Unacceptable distribution makes the cell count invalid.Ideally,another dilution should be made,and it should be well mixed before charging the chamber.Other possible reasons for poor distribution include uneven flow when charging the chamber,dirt or oil on the surface of the chamber or coverslip,and disturbing the coverslip while counting the cells.

Question 10

Diagnostic testing at or near the site of patient care is known as

Accepted Answer

Diagnostic testing at or near the site of patient care is known as POCT.

Quiz 14: Manual, Semiautomated and Point-of-Care Testing in Hematology