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 Tests Consists 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: x 10 6 mm 3 Women: x 10 6 mm 3  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: g/dl Newborns: 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 10 3 / mm 3 Women: x 10 3 / mm 3  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 / mm 3  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 %Baso %  Lymph %  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