The Complete Blood Count and Peripheral Blood Smear Evaluation (Chapter 10) : Exam 1 objectives

List the parameters typically included in the complete blood count (CBC)

Concentration of WBCs, RBCs, platelets▪

Categorization of WBC subsets▪

RBC= 4.0-5.5 X 10^6 /MCL

hemoglobin=12.0-17.4G/dL

hematocrit =36-52 l/L

Describe how to properly identify a patient prior to blood collection.

Name, hospital number, date of birth

List the pre-examination precautions that must be observed to produce quality results when performing a CBC

Specimen collection - Follow safety requirements - Purple/lavender top tube containing EDTA •

Specimen handling

Proper transport (time and temperature) ▪ Blood smear prepared within 3 hours of collection ▪ Instrument analysis within 6-8 hours of collection

List the typical units of measure for reporting the W BC, RBC, PLT, Hb, Hct, andreticulocyte count

Leukocyte count (WBC), erythrocyte count (RBC),

hematocrit (Hct), hemoglobin (Hb)

- WBC reported as 103/microLiter

- RBC reported as 106/microLiter

- Hct reported as %

▪ Measures volume RBCs occupy within whole blood

▪ Usually calculated in automation

▪ Hct (%)

- Hb reported as grams/deciLiter or grams/Liter

- Rule of Three

▪ Hb = RBC count × 3

▪ Hct = Hb × 3

▪ Must agree within ±3% of measured value or

indicates measurement error, instrument

malfunction, or patient has pathology

▪ Only works for normocytic, normochromic RBC

Define the term MCV

(mean cell volume) MCV= cells size:

Normocytic 80.0-100.0 FL

Microcytic Red cells with a reduced volume (less than 80 femtoLitre)

The H b (Macrocytic Red cells with an increased volume (greater than

100 femtoLitre)

Anisocytosis Increased variation in the range of red cell sizes

Define the term MCHC

(mean cell hemoglobin concentration)

MCHC: How much hemoglobin is in the cell

Normochromic 32.0-36.0 grams/deciliter

Hypochromic Less than 32.0 grams/deciliter

Hyperchromic More than 36.0 grams/deciliter

Define the term RDW

Red Cell Distribution Width

The red cell distribution width- Describes variation in red cell size (anisocytosis)

Define the term MPV

(mean platelet volume) represents the average volume of individual platelets (similar to MCV for RBCs)

Define the term PDW

PDW (platelet distribution width) blood test:

Describe the role of the laboratory professional in the examination phase ofthe CBC

A laboratory professional will analyze and interpret data

generated by an automated analyzer and blood smear review

- Identify abnormal results, pathologies, and discrepancies in

data

- Should be able to recommend reflex or follow-up testing

• Delta checks compare the patient's current laboratory values with

previous values

- Aid in identifying

▪ Instrument error

▪ Misidentified patient samples

- Important in diagnosis and monitoring therapy

Describe the role of the laboratory professional in the post-examination phaseof the CBC

Report data

- Laboratory information system (LIS)

- Data includes reference intervals for each test

- Flags for abnormal results

• Recognition of data

- Critical limits represent critical low and high values for

CBC parameters

- Critical values (life-threatening) must be confirmed,

documented, called the physician

Describe the variations in the CBC reference intervals found in African Americans.

ethnic groups

- African Americans

▪ Lower Hb, Hct, MCV than Caucasians

▪ 30% prevalence of α-thalassemia (African Americans have a higher risk of sickle cell)

▪ WBCs lower, particularly granulocytes, but

lymphocytes are higher

• Sexes

- Males have higher Hb, Hct, RBC, and WBC counts than

females

- Females have higher platelets, slightly lower MCV, MCH

Describe the variations in the CBC reference intervals found in elderly people.

Elderly

- BM cellularity decreases with age

- Anemia becomes more prevalent due to:

▪ Iron deficiency

▪ Vitamin B12 deficiency

- Anemia becomes more prevalent due to:

▪ Anemia of chronic inflammation

▪ Kidney disease

▪ ↓ testosterone levels

- Malignancies occur at higher incidence

Describe the variations in the CBC reference intervals found in newborns

Newborns

- WBC count higher

- Granulocytes ↑, drops within 72 hours

- Immature WBCs in circulation for 2 weeks

- RBCs macrocytic

- Reticulocyte count 2-6%

- Nucleated RBCs, up to 10/100 WBCs, can be present

- At birth, highest RBC, Hb, Hct values followed by gradual ↓

▪ MCV neonates 108 femtoLitre

▪ ↓ to 77 femtoLitre between 6 months-2 years

▪ MCHC remains constant

Correlate the age of a patient and the typical changes in CBC results compared with a normal adult CBC.

In Children

- Lymphs are predominant cell until age 4 or 5

- 4-5 years, equal numbers of lymphocytes and

granulocytes

- 8 years old, same WBC subsets as adults