chapter 5 diagnostic testing. overview of diagnostic testing purpose of diagnostic testing to help...
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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
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