Leukogram & Thrombogram (Thomas)

Question 1

What information do CBC tests provide about WBCs?

Answer 1

WBC concentration, percentages and concentrations of specific WBC types, comments related to blood film review

Includes total concentration, specific WBC percentages (neutrophils, lymphocytes, monocytes, eosinophils, basophils), and abnormal cell types.

Question 2

What are the two portions of the WBC component in a CBC?

Answer 2

Blood smear review and quantitative portion (WBC count)

The quantitative portion includes total WBC concentration and specific WBC percentages.

Question 3

What is included in the routine leukogram of a CBC?

Answer 3

WBC concentration and microscopic exam of blood smear

The exam is for concentration estimate, abnormal cells, and inclusions.

Question 4

How is WBC concentration typically measured?

Answer 4

By an automated hematology analyzer

Must correct for significant numbers of nRBCs.

Question 5

What correction is made for nRBCs in WBC counts?

Answer 5

Corrected [WBC] value based on nRBC count per 100 WBC differential

Standards for correction may vary by laboratory.

Question 6

Why should WBC concentrations be used instead of percentage values?

Answer 6

Percentages are relative; absolute values [WBC concentration] are preferred.

Absolute values provide a clearer picture of actual cell counts.

Question 7

Which WBC types are generally not reliably detected by hematology analyzers?

Answer 7

Basophils, banded neutrophils, and nRBCs

If these are present, a manual WBC differential should be performed.

Question 8

What are nRBCs and how do they affect WBC counts?

Answer 8

nRBCs are non-leukocyte cells often mistaken for WBCs.

They can lead to inaccurate WBC counts if not corrected.

Question 9

How do you correct for nRBCs?

Answer 9

• # nRBC/100 WBC means how many nRBC’s you count in a manual 100 WBC count differential
• Use the corrected [WBC] value to calculate concentrations of individual WBC types

Question 10

What are the limitations of microscopic WBC differential counts?

Answer 10

Human error, observer variability, and limited cell counts compared to automated methods

Microscopy is necessary for accuracy in health and disease.

Question 11

What are the limitations of automated WBC differential counts?

Answer 11

• [Platelet] not accurate if clumping is present
• MPV inaccurate if clumping present
• Plateletcrit inaccurate if clumping present since it is calculated
• Analyzers are often accurate in health, but inaccurate in disease; microscopy needed
• No analyzer can reliably detect basophils (even if value is provided)
• Analyzers typically count both segmented and band neutrophils as neutrophils
• Other cells not reliably counted: hypogranular eosinophils, neoplastic cells

Question 12

What is the effect of platelet clumping on platelet concentration measurements?

Answer 12

Platelet concentration may appear falsely decreased due to clumping.

Clumps may not be counted or may be counted as single platelets.

Question 13

What is the MPV?

Answer 13

Mean Platelet Volume
* Average platelet size measured in fL units
* Increases when stored in the tube for too long (RBCs swell – false increase)

MPV can be unreliable if platelet clumping is detected.

Question 14

What is [PLT]?

Answer 14

Platelet concentration
* Number of platelets per volume of blood
* Automated: only acceptable if no platelet clumps, if there are clumps, then the value is accepted as the minimum value
* Manually rarely done (hemocytometer)

Question 15

What is Pct?

Answer 15

Plateletcrit
* % volume of blood occupied by platelets.
* Calculated using [PLT] and MPV

Question 16

What does a microscopic exam/blood smear in a routine thrombogram assess?

Answer 16

Platelet clumps, concentration estimate, size, inclusions (possible organisms too).

Question 17

Which quantitative platelet values are unreliable when platelet clumping is
present?

Answer 17

• [PLT] - Platelet Concentration
• MPV - Mean Platelet Volume
• PCT - Plateletcrit

Question 18

What is the usual cause of platelet clumping?

Answer 18

Bad blood sample collection process:
* Slow/traumatic draw
* Small size needle
* Delayed mixing of sample all can lead to platelet activation

Question 19

How are quantitative leukogram and thrombogram results related to qualitative findings?

Answer 19

Quantitative results provide cell numbers; qualitative findings confirm accuracy and provide critical information about cell morphology and maturity.

Both must be interpreted together for accurate diagnosis.

Question 20

What is the concentration factor for estimating platelet concentration from a blood film?

Answer 20

Average number of platelets per 100x field x ~15,000 to 20,000/uL

Averaged over 5-10 fields in the optimal zone.

Question 21

Where are platelets and WBCs located in blood after centrifugation?

Answer 21

In the buffy coat

The buffy coat separates the cellular components from plasma.