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Lab Di 1st Exam

Dr. Well's NYCC 1st Lab Di Exam

QuestionAnswer
When should lab tests be performed? If they will alter the diagnosis, prognosis, treatment or management of a patient.
What percentage of patients (even asymptomatic) will have abnormal lab results on an 8 test panel, a 20 test panel? 8: 25% have 1 or more abnormal results; 20: 64% have 1 or more abnormalities.
Why would a screening test be performed? Looking for disease in asymptomatic persons.
What is a case finding and why would these other tests be done? Symptoms of 1 disease can lead a physician to want to test for another disorder. e.g. pt. w/ peripheral neuropathy get glucose testing.
What is sensitivity in test interpretation? Rate of true positives in a population; ability of a test to give a positive result when a pathology is really present.
What is specificity in test interpretation? Ability of a test to give a negative/normal result when a pathology is not present.
What is hematology? The study of blood and its formed elements. Includes concentration, structure and function of RBCs, WBCs and platelets.
What is included in the hematopoietic system? spleen, lymph nodes, thymus, bone marrow, liver and RES
What is considered the circulatory system? Peripheral blood: arteries and veins.
What color top tube is used to collect CBC and what does it contain? Lavender; anticoagulant EDTA
What is the most reliable measure of the rate of RBC production? Reticulocyte count
What are 2 important factors about a mature RBC? 1. Flexible and deformable for passage through microcirculation. 2. Normal and intact membrane is essential for RBC function and survival.
What is MCV and what vocabulary is specific to this index? Mean Corpuscular Volume: average size of RBC; Microcytic, Normocytic, Macrocytic
What is MCH and what vocabulary is specific to this index? Mean Corpuscular Hemoglobin: weight of hemoglobin in the average RBC; Hypochromic, Normochromic, Hyperchromic
Define normocytic. RBCs of normal size, normal MCV
Define microcytic. RBCs small in size, low MCV, usually d/t decreased hgb production.
Define macrocytic. RBCs bigger in size, high MCV, usually indicates a defect in RBC maturation.
Define normochromic. RBCs normal in color MCH and MCHC are normal.
Define hypochromic. RBCs appear lighter in color with an increased area of central pallor, MCH and/or MCHC is below normal.
Define hyperchromic. RBCs appear darker and lose their area of central pallor (increase in thickness) MCH and/or MCHC is above normal. Not a common finding!
What is RDW and what vocabulary is specific to this index? Red cell Distribution Width: a measure of the degree of uniformity of the size and/or shape of RBCs; Poikilocytosis, Anisocytosis
Define poikilocytosis. Variations in the shape of the RBCs as viewed under the microscope. Different cell types are give like spherocytes, ovalocytes, elliptocytes, target cells and sickle cells.
Define anisocytosis. Variations in the size of RBCs d/t pathology, reflected in MCV.
What is measured to determine if anemia exists? RBC count Hb Hct
What is calculated to determine the anemia type? MCV MCH MCHC (RDW is calculated but not used to determine type of anemia)
What is the most common RBC disorder? Anemia
Define anemia A decrease in the circulating RBCs, hemoglobin concentration or hematocrit.
What is anemia? Reduction in H & H; pathologic decrease in the RBC count.
What does factor deficiency mean in anemia? Missing some required nutrient like Fe or B12.
What does production defect mean in anemia? Impaired RBC production like marrow failure.
What could cause red cell loss from peripheral blood? Hemolysis.
What are symptoms (subjective) of anemia? Shortness of breath, weakness, fatigue, faintness, lethargy, HA, Pica, sore tongue, palpitations, paresthesias.
What are signs (objective) of anemia? Pallor, cardiac fcn anomalies, jaundice (hemolytic), fingernail deformities, tongue signs, hypotension, tachycardia, neurologic findings.
What could severe anemia cause? Chest pain, angina, heart attack; could be reduced oxygen capacity -> hypoxia -> heart attack (w/o atherosclerosis).
What are the 3 questions needed to be asked when finding anemia? 1. Is there anemia? 2. What morphology is it? 3. What is the cause?
Of the questions asked when finding anemia which one(s) can be answered w/ a CBC? Is anemia present and morphology. Morphology is form or type not cause.
What is the most common cause of iron deficiency anemia? Chronic GI bleeds.
How does iron deficiency anemia look at first and then w/ time? At first normochromic, normocytic then gradually microcytic, hypochromic.
What test is used to find occult blood in the stool? Guaiac test AKA hemoccult tests for hgb in the stool and when a chemical developer is dropped in turns blue when positive.
What is the most common cause of anemia? Iron deficiency anemia; not enough Fe for normal hgb production resulting in microcytic, hypochromic anemia.
What are mechanisms of iron deficiency anemia? dietary deficiency, insufficient Fe absorption, insufficient transport, abnormal iron loss, increased Fe requirement (prego), blood loss.
What are diagnostic tests? Testing to assist diagnosis of a patient w/ symptoms that may be common to several disorders.
What are monitoring tests? Testing to monitor therapeutic process in patients w/ known diagnoses; to evaluate the course of a Dz or detect complications.
What are the 4 broad variables that affect lab results? Biologic, Pre-analytic, Analytic, Post-analytic
What are examples of a biologic variable that affects lab results? Race/ethnicity, gender, individuality
What are examples of a pre-analytic variable that affects lab results? Diet, exercise
What are examples of a analytic variable that affects lab results? Bad lab technique or equipment
What are examples of a post-analytic variable that affects lab results? Transcription, interpretation
What is erythropoiesis and what is it regulated by? A process by which early erythroid precursor cells differentiate to become mature RBCs; i. Regulated by erythropoietin (EPO) – production occurs in response to tissue hypoxia.
What is RBC maturation dependent on? Dependent on B12 and folate, needed for DNA synthesis, nuclear maturation and division.
How will marrow respond to anemia and what if the retic count is normal when anemia is present? Marrow will force immature cells into circulation d/t anemia, retic count should be high if system responding properly to anemia; If there is anemia and retic count is normal the marrow is not responding or anemia is in early stage.
What is hemoglobin? Hemoglobin is the oxygen carrying protein in RBCs (low levels indicates anemia).
What are s/s of pernicious anemia? Weight loss; anorexia; smooth or painful and beefy red tongue; constipation or multiple BMs/day; nausea, vomiting, pyrosis, flatulence and sense of fullness; UTIs; Paresthesias, weakness, clumsiness, unsteady gait; tachycardia; dyspnea, tacypnea, CHF.
What are s/s of Sickle cell anemia? Abdominal and bone pain MC Sx in sickle cell crisis d/t infarcts.
What are s/s of lead poisoning? Sx: abdominal pain, brain Sx in children, peripheral nerve or cord Sx in adults; Signs: found on x-ray.
How does iron deficiency anemia progress? Normochromic, normocytic anemia progresses to microcytic, hypochromic as iron stores deplete; Decreased MCV and MCH and increase in RDW d/t size and shape changes; anisocytosis and poikilocytosis – elliptocytes.
What occurs w/ megaloblastic anemia? Enlargement of all rapidly proliferating cells of the body, Diminished capacity of cells to synthesize DNA, RNA synthesis is less impeded so cytoplasmic maturation and growth continue causing enlargement of the cells.
Compare/contrast b/w megaloblastic and macrocytic anemias. Macrocytosis means large RBCs, megaloblastic anemia is usually macrocytic, megaloblastic refers to RBC precursors in the marrow.
What can cause Macrocytic anemia? B12 and folate deficiency are the most common causes; other causes include: hypothyroidism, multiple myeloma, myeloproliferative diseases, drugs, chronic liver disease.
Describe what occurs d/t folate deficiency and macrocytic anemia. Megaloblastic, impaired DNA synthesis in RBC precursors, results in macrocytic anemia, hypersegmented neutrophils, large platelets = pancytopenia
What can cause folate deficiency? Inadequate intake, increased utilization of folate, decreased folate absorption, inhibition of folate synthesis, dialysis patients.
What are laboratory findings for macrocytic anemia? Macrocytic anemia (elevated MCV), hypersegmented neutrophils, macro-ovalocytes; decreased reticulocytes; serum Folate decreased, RBC folate decreased [storage folate – certain amount stored in RBCs; accurate measure of folate in body]
Describe aplastic anemia. Pancytopenia (decrease in all blood cell lines) associated w/ hypocellularity of the bone marrow. [Fewer colony-forming units, decreased pleuripotential stem cells; once stops working may not self correct.]
What are 3 types of hemolytic anemia? Hereditary spherocytosis, herditary elliptocytosis, paroxysmal nocturnal hemoglobinuria.
Describe hereditary spherocytosis. Defect in RBC membrane protein composition; Anemia of variable severity w/ peripheral blood smear showing spherocytes which are smaller in diameter, high concentration of hemoglobin, less flexible and burst easy in water.
Describe hereditary elliptocytosis. Defect of membrane composition; Increase in elliptocytes (ovalocytes) seen on peripheral smear; anemia variable, abnormal cells removed by spleen.
Describe paroxysmal nocturnal hemoglobinuria. Hematopoietic stem cell disorder, generation of defective RBCs, WBCs and platelets -> pancytopenia; RBCs unusually sensitive to complement fixation causing lysis; Hemoglobinuria–blood in urine, often 1st morning urine d/t the concentration [not severe]
What is hemolysis d/t hemoglobin disorders? Hemoglobinopathy: Structure of 1 of the 4 types of globin chains formed is abnormal, usually d/t the substitution of a single amino acid.
What AA is substituted for sickle cell anemia? Substitution of valine for glutamic acid on the beta chain transforms Hgb A into Hgb S
Describe what occurs in the blood of someone w/ sickle cell anemia. RBCs are more rigid and prone to trauma; decreased oxygen tension causes hgb to crystallize and precipitate out causing sickling of the cell; hemolysis and vaso-occlusion may occur w/ severe pain, ischemia and infarctions to vital organs.
What are thalassemias? A group of inherited microcytic anemia’s characterized by defective hgb synthesis usually d/t deletion of genes controlling the alpha or beta globin chain; globin chains of normal structures are formed but rate of synthesis is decreased.
Describe beta thalassemia. Beta chain production decreased, structural genes present but mRNA not produced efficiently or degraded rapidly; Most common Thalassemia, seen in people of Mediterranean descent (some Middle Eastern population too)
Describe Thalassemia Major (Cooley's anemia). Homozygous: anemia is severe w/ jaundice, failure to thrive, survival dependent on transfusion; marked anisocytosis, poikilocytosis, Heinz bodies.
Describe Thalassemia Minor. Heterozygous usually asymptomatic, mild microcytic anemia, normal to decreased Hgb w/ RBCs normal to elevated.
What is hemolysis d/t enzyme defects? RBC uses ATP to maintain the flexibility of its membrane; ATP synthesis requires certain enzymes. When enzyme deficiencies occur they lead to hemolysis.
What occurs w/ glucose-6-phosphate dehydrogenase deficiency? Usually asymptomatic and normal CBC except when hemolysis is induced by precipitating illness (infection, fava beans); Anemia w/ Heinz bodies seen on peripheral smear
What occurs w/ pyruvate kinase deficiency? Chronic hemolysis exacerbated by acute illness, viral infections, pregnancy; Typical hemolytic laboratory presentation.
What are autoimmune hemolytic anemias? A group of disorders whose common features is presence of autoantibodies to antigens on RBCs.
What occurs w/ warm autoimmune hemolytic anemia? Autoantibodies bind to RBCs optimally at 37C; Antibodies most often IgG; SLE and other autoimmune disorders, CLL, malignancies.
What occurs w/ cold autoimmune hemolytic anemia? Autoantibodies bind to RBC w/ greater affinity at <37C; Antibodies most often IgM; Idiopathic, Mycoplasma pneumoniae infection, viral infections, malignancies.
What causes anemia d/t toxic hemolysis? Lead poisoning: lead enters body through ingestion or inhalation.
What tests are selected to diagnose iron deficiency anemia? Serum Iron (sIron); Total Iron Binding Capacity (TIBC); Transferrin saturation (TS); Serum Ferritin (sFerritin
Describe serum iron (sIron). Measures iron bound to transferrin reflects rate of iron delivery to tissues; will drop w/ reduction of tissue stores.
Describe Total Iron Binding Capacity (TIBC). Measures the approximate amount of transferrin specifically the number of available iron binding sites; value increases as iron decreases [inverse relationship to sIron].
Describe Transferrin Saturation (TS). Calculation using the amount of sIron and TIBC. Shows the amount of useful Fe. i.e. what percent of transferrin is bound to iron.
Describe Serum Ferritin (sFerritin). Sensitive and decrease can be seen in early iron deficiency anemia before there is evidence of reduced H&H. Directly related to total body iron stores; most useful test in the evaluation of the body’s iron status.
What specific tests will give an idea of true iron status? sIron, TIBC and sFerritin used conjunctively.
What tests are selected to diagnose macrocytic anemia. Serum Folate, Serum B12 assay (for B12 deficiency), Marrow examination, Schilling's test for malabsorption.
What might be elevated long before anemia appears w/ B12 deficiency? MCV; may take 1-2 years to elevate but any elevation should be investigated before anemia develops.
What is part I of Schilling test? Tagged oral B12 and no IF, Followed by injection of nonisotopic B12 which saturates B12 binding sites and if tagged B12 was absorbed in gut secretes it in urine, a minimal amount should appear in urine. <minimal amount = malabsorption.
What is part II of Schilling test? If part I was abnormal then it is repeated w/ IF added to tagged oral B12 to see whether the malabsorption is from pernicious anemia or another reason. If from pernicious anemia then tagged B12 in urine should be normal as IF made it absorbable.
What tests are selected to diagnose aplastic anemia? CBC shows: Decreased RBCs, WBCs, platelets, reticulocytes; Hypocellular bone marrow biopsy
What tests and their results are selected to diagnose hemolytic anemia? Increase in reticulocytes, direct and indirect bilirubin [high since bilirubin in RBCs], Lactate dehydrogenase 3-5 times normal, Serum haptoglobin decreases, urine urobilinogen increases, sIron may increase, hemoglobin electrophoresis for subtypes.
What test is specific for testing hemoglobinopathies? Hemoglobin Electrophoresis.
How is hemoglobin electrophoresis done? RBCs are lysed; hemolysate is applied to cellulose acetate gel. Hemoglobins are separated by electric charge – electrophoresis. Hgbs stained and identified by their positions of migration. Hgbs can then be quantified by a densitometer.
What findings in hemoglobin electrophoresis are specific for thalassemia major? No Hgb A, elevated Hgb F, elevated Hgb A2.
What findings in hemoglobin electrophoresis are specific for thalassemia minor? Slight decrease Hgb A, elevated Hgb A2 > 5% diagnostic, Hgb F normal to elevated.
What findings are specific for Glucose-6-Phosphate Dehydrogenase deficiency? Findings of hemolysis: increased reticulocytes, decreased haptoglobin, increased bilirubin and LDH.
What is a test to test for Glucose-6-Phosphate Dehydrogenase deficiency? A quantitative assay for G6PD.
What is a test to test for Pyruvate Kinase deficiency? A quantitative assay for RBC pyruvate acid.
What 2 tests are used to test for Drug-induced hemolytic anemia? Laboratory tests for hemolysis and Coomb’s test or Direct Antiglobin Test (DAT)
What makes a DAT positive, what are the 2 types and what do they identify? Positive: detects IgG or complement bound to RBCs; Direct and indirect Coomb’s test; Both identify autoantibody attacks to RBCs.
What tests test for lead poisoning? Lead levels, Blood smear will show basophilic stipling and increased RDW b/c differing red cell size.
What is polycythemia? An increase in erythropoiesis (elevated RBCs, hgb and hct).
What is polycythemia vera? A myeloproliferative disorder w/ an absolute increase in all cell types: RBC, WBC and platelets.
When does polycythemia vera occur and what are the 3 major criteria? Later in life (40-60 years); splenomegaly, normal O2 saturation and increased red cell mass.
What are findings w/ polycythemia vera and how does the disease progress? Low EPO levels, bone marrow hypocellular; disease is chronic w/ cardiac and thrombotic complications; myelofibrosis may develop as well as leukemia.
What is Absolute Polycythemia? It is secondary; physiologic response to hypoxia, EPO mediated like response to high altitude.
What are blood test findings w/ Absolute Polycythemia? Elevated RBCs, hgb, hct; WBCs and platelets normal; Elevated EPO levels.
What is Relative Polycythemia? Caused by a decreased plasma volume while RBC mass remains unchanged; most often caused by dehydration.
What are blood test findings w/ relative polycythemia? Elevated RBCs, hgb, hct; WBCs and platelets normal.
Created by: Kelly Brown Kelly Brown on 2011-05-17



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