Chapter 5 Diagnostic Testing

Overview of Diagnostic Testing

PURPOSE OF DIAGNOSTIC TESTING To help determine the

exact cause of signs or symptoms

To confirm the effectiveness of a prescribed treatment (tx)

Important to interpreting results Normal values vary

slightly from lab to lab Perfectly healthy people

will sometimes have abnormalities on testing

Not every abnormal test is significant

Composition of Blood Composed of liquid and cells Liquid portion is called plasma

Composed of about 90% water

Several types of blood cells Red blood cells (erythrocytes) White blood cells (leukocytes) Platelets (thrombocytes)

Red blood cells – erythrocytes Medium sized blood cell Function – transport oxygen from the lungs to the body cells Diseases associated with RBC:

-Sickle – cell anemia

-anemia

White blood cells – leukocytes Large-sized blood cell Function – to protect the body from infection Diseases associated with WBC:

-leukemia

-HIV / AIDS

Platelets – thrombocytes Small-sized blood cell Function – to help the blood clot after a

cut or similar injury Diseases associated with platelets

-thrombocytopenia

-hemophilia

Obtaining blood for testing

Most samples taken from veins - bluish vessels visible through the skin

Some samples are taken from the arteries to asses oxygenation of blood

Some samples are taken by pin prick to the finger (which samples capillary blood)

General types of blood disorders Red blood cell disorders

Anemia – lower than normal amounts of RBC’s

-possible causes – bleeding, low RBC production, or RBC destruction

Polycythemia – higher than normal amounts of RBC’s

-possible cause – chronically low oxygen in the blood

Platelet disorders Thrombocytopenia – lower than normal number of platelets

-usually genetically caused

White blood cell disorders Leukopenia – lower than normal amounts of WBC’s Leukocytosis – higher than normal amounts of WBC’s

-possible causes – infection or leukemia

Blood testing is performed on blood taken from vein, and centrifuged to separate cells from plasma

Complete Blood Count TestsConsists of the following tests: a. RBC count

b. Hct (hematocrit)

c. Hgb (hemoglobin)

d. WBC (white blood cell count)

e. Platelet count

f. Diff (differentiated white blood cell count)

RBC count Normal values

Men: 4.6-6.2 x 106 mm3

Women: 4.2-5.4 x 106 mm3

Decreased values (anemia) caused by

Blood loss

Dietary insufficiency increased values (polycythemia) caused by

Dehydration

Diahrrhea (severe)

High altitudes

Hct (hematocrit) – what % of blood is composed of RBC’s Normal values

Men – 40-54%

Women – 38-47%

Decreased values caused by

anemia

hemorrhage

blood cell destruction during transfusion of blood Increased values caused by

Dehydration

Shock

Hgb (hemoglobin) - measures protein in RBC’s that carries oxygen Normal Values:

Men: 13.5 – 17.5 g/dl

Women: 12-16 g/dl

Newborns: 14-16 g/dl

Decreased values caused by

Anemia

Excessive fluid intake

Pregnancy

Increased values caused by

Chronic obstructive pulmonary disease

High altitudes

WBC – measures total number of WBC (including all types of blood cells) Normal Values:

Men: 4.5 – 11 x 103 / mm3

Women: 4.5-11 x 103 / mm3

Decreased WBC (leukopenia) (if < 5000 WBC – NEEDS IMMEDIATE ATTENTION)

Alcoholism

Viral infections

Chronic infection where body is worn out (cancer)

Increased WBC (leukocytosis)

WBC >10,000

Infection

Leukemia

Steroid therapy

Coma

Stress

Platelet count – determines number of platelets in blood Normal values – 150,000 – 350,000 / mm3

Decreased values (thrombocytopenia)

Blood transfusions

Bone marrow lesions

Cancer chemo

Toxic drug effects Increased values

Heart disease

Iron deficiency

Trauma

TB

Diff – differential WBC count – measures each different type of WBC 1. Neutrophils – combat bacterial infections, inflammation and stress

2. Lymphocytes – fight viral infections

3. Eosinophils – respond to allergic conditions and parasitic invasions

4. Monocytes – respond to severe and chronic infections

5. Basophils – respond to inflammation and blood disorders

Normal Diff values – Neu- 60-70% Baso- 0.5-1% Lymph- 20-40% Eos- 1-4% Mono- 2-6%

The percentage of a type of WBC will increase when the body is in need of its function

This information can be used to draw a conclusion when diff is abnormal

Example: Eosinophils respond to allergic conditions. Increased eosinophils

suggest an allergic reaction

Coagulation tests measure blood’s ability to clot Blood chem tests – BUN, Electrolytes, Enzyme levels