Anemia: Diagnosis and Clinical Considerations Chapter 4 Anemia: Diagnosis and Clinical Considerations

1. Study Questions 2. Homework Assignment 3. Exam for Unit III

Anemia: Diagnosis and Clinical Considerations In Chapter 4, you will learn how anemia is diagnosed using different classification systems.  You will also see how anemia affects an individual's physiology and how the body tries to compensate for the anemia.  Laboratory tests used to diagnose anemia are discussed.   Finally, you will learn the normal ranges for each parameter of a CBC and how to calculate the red blood cell indices.

Definition of Anemia 1 of 2 Inability of blood to supply tissues with adequate oxygen for proper metabolic function. Diagnosis made by patient history, physical examination, signs and symptoms, and hematological laboratory findings. Usually associated with decreased levels of hemoglobin or hematocrit (packed red cell volume) - Abnormal hemoglobin may give appearance of anemia (methemoglobin). Usually associated with decreased RBCs.

Definition of Anemia 2 of 2 Classified as moderate (Hb 7-10 g/dl) or severe (Hb <7g/dl). Physical signs include difficulty breathing (dyspnea), vertigo, light-headedness, muscle weakness, headaches, and lethargy. Rapidly developing anemia may be associated with hypotension and tachycardia. Two general forms of anemia:   Absolute Anemia (decrease in red cell mass) and Relative Anemia (increased plasma volume gives appearance of anemia). 

Considerations by Age, Sex, and Other Factors 1 of 2 Newborns less than one week old have hemoglobin of 14-22 g/dl. By six months of age, hemoglobin runs between 11 and 14 g/dl. Between 1 year and 15 years of age hemoglobin runs between 11-15 g/dl. Normal adult hemoglobin depends on gender: ♀ 12-16 g/dl ♂ 14-18 g/dl In geriatric age group, men and women have same hemoglobin range:  12-16 g/dl.

Considerations by Age, Sex, and Other Factors 1 of 2 Normal ranges do depend on patient populations. Other factors influencing “normal” hemoglobin include: Environment: elevation of Denver vs. New Orleans Physical Health: e.g. lung or kidney disease Nutritional deficiencies Blood loss Bone marrow replacement Chemicals / Radiation

Causes of Anemia Nutritional deficiencies Hemolytic disorders Blood loss Bone marrow (hypoproliferative) Infection Toxicity Hemopoetic stem cell damage (maturation disorder) Heredity or acquired defect Unknown

RBC and Hemoglobin Production 1 of 2 In healthy individuals, about 1% of RBCs lost daily. Bone marrow continuously produces RBCs to equal daily loss. Reticulocyte count is a lab measurement of this loss. Normal retic count is 0.5-2.0% of circulating RBCs. Replacement requires functioning bone marrow, normal RBC maturation and ability to release mature RBCs to peripheral blood. Proper nutrition required (B12, Folate).  Also requires normal hemoglobin synthesis.

RBC and Hemoglobin Production 2 of 2 Severe anemia (<7 Hb) may see other organ system failures:  Cardiac and respiratory. Do have compensatory mechanism:  See an increase in 2,3-DPG levels which results in an increase in RBCs’ oxygen carrying capacity. Erythropoietin levels (Epo) useful diagnostic tool. Anemic people usually respond by increasing erythropoietin levels. Erythropoietin is a hormone produced in the kidney. Levels of erythropoietin varies with oxygen tension in kidney tissues (↓ Oxygen - ↑ Epo, and vice versa)

Clinical Diagnosis Made by combination of factors including: patient history, physical signs and changes in hematologic profile (CBC). Signs and symptoms usually non-specific: fatigue, weakness, gastrointestinal symptoms (nausea, constipation and diarrhea), shortness of breath - especially after exertion. Physical signs of anemia are usually not specific for the cause.

Physiological Response ↓oxygen carrying capacity Shift to right ↑ 2,3-DPG ↑ Cardiac output Circulation shifts to critical areas ↑ RBC production ↑ Erythropoietin Left shift on blood smear ↑ Reticulocyte count

Classification of Anemias Have a variety of ways - depending on criteria used: Functional Morphological Clinical Quantitative

Functional Classification of Anemias Decreased RBC production (hypoproliferative) Defective hemoglobin synthesis Fe deficiency B12 deficiency Folate deficiency Impaired bone marrow or stem cell function, as in leukemia Increased RBC destruction, as in sickle cell anemia or hemolytic anemia Combination of the two (sometimes called “ineffective erythropoiesis”)

Morphological Classification of Anemias Morphological based on sizes and color of RBCs Normochromic Normocytic Hypochromic Microcytic Normochromic Microcytic Normochromic Macrocytic

Clinical Classification of Anemias According to their associated causes: Blood loss Iron deficiency Hemolysis Infection Nutritional deficiency Metastatic bone marrow replacement

Quantitative Classification of Anemias Quantitatively by: Hematocrit Hemoglobin Blood cell indices Reticulocyte count

Hemoglobin and Hematocrit 1 of 2 Anemia usually diagnosed on either hemoglobin or hematocrit values. Remember, normal ranges vary depending on age, gender, state of hydration, patient positioning and local patient population. Hemoglobin analysis based on spectrophotometric absorbance readings of cyanmethemoglobin. Hematocrit is packed cell volume (PCV) determined by centrifugation: Normal range for adult men is 42-52% Normal range for women is 37-47%

Hemoglobin and Hematocrit 2 of 2 On basis of H&H, anemia can be classified as mild, moderate, or severe. On basis of duration of onset, anemia can be classified as either chronic or acute. Rules of Three: RBC X 3 = Hemoglobin Hemoglobin X 3 = Hematocrit Ratio of Hb and Hct will vary with cause of anemia and affect the RBC indices, particularly the MCV (Mean Corpuscular Volume). Microscopic examination of peripheral blood smear is required for evaluation of anemia.  Bone marrow aspirates and smear evaluation may also be needed.

RBC Indices RBC indices include: Mean Corpuscular Volume (MCV) Mean Corpuscular Hemoglobin (MCH) Mean Corpuscular Hemoglobin Concentration (MCHC) RBC Distribution Width (RDW)

MCV Mean cell volume MCV is average size of RBC MCV = Hct x 10 RBC (millions) If 80-100 fL, normal range, RBCs considered normocytic If < 80 fL are microcytic If > 100 fL are macrocytic Not reliable when have marked anisocytosis

MCH MCH is average weight of hemoglobin per RBC. MCH = Hgb x 10 RBC (millions)

MCHC MCHC is average hemoglobin concentration per RBC MCHC = Hgb x 100 Hct (%) If MCHC is normal, cell described as normochromic If MCHC is less than normal, cell described as hypochromic There are no hyperchromic RBCs

RDW Most automated instruments now provide an RBC Distribution Width (RDW) An index of RBC size variation May be used to quantitate the amount of anisocytosis on peripheral blood smear Normal range is 11.5% to 14.5% for both men and women

RBC Indices and Other Tests RBC indices are automatically calculated by instruments. Microscopic evaluation will determine if RBCs are normocytic, microcytic, or macrocytic and normochromic or hypochromic. Use of RBC indices in differential diagnosis can provide picture of what is occurring clinically. If anemia caused be bone marrow failure, requires information about RBC production. Information obtained from reticulocyte count. Reticulocyte count measures effective RBC production. As study different anemias, will learn morphology.

Normals COMPONENT NORMAL RANGES WBC 4.8-10.8 x 103/μL RBC Male 4.7-6.1 x 106/μL; Female 4.2-5.4 x 106/μL Hgb Male 14-18 g/dL; Female 12-16 g/dL Hct Male 42-52%; Female 37-47% MCV 80-100 fL MCH 27-31 pg MCHC 32-36% RDW 11.5-14.5% Plt 150,000-350,000/μL Retic 0.5-2.0%

Treatment of Anemias Treated according to cause; Should know cause before beginning treatment. Patient can have more than one cause of anemia. Must use diagnostic tests to determine cause(s). Do diagnostic tests before transfusions, because transfusions obscure and confuse findings.

Hgb (In the Diagnosis of Anemia) Hbg is the main component of RBCs and carries oxygen to tissues. Three methods to measure hemoglobin: Cyanmethemoglobin (recommended method) Oxyhemoglobin Iron Content 

Cyanmethemoglobin (method to measure Hgb) 1 of 2 1. Blood is diluted in a solution of potassium ferricyanide and potassium cyanide, which oxidizes the hemoglobin to form methemoglobin. 2. Then methemoglobin forms cyanmethemoglobin in the presence of the potassium cyanide. 3. Absorbance of solution is read in spectrophotometer at 540 nm.

Cyanmethemoglobin (method to measure Hgb) 2 of 2 Advantages: Most forms of hemoglobin are measured Sample can be directly compared with a standard Solutions are stable Method is precise Errors in the measurement of Hgb: Must draw and handle specimen correctly Reagents must be properly prepared and stored Equipment failure Operator error

Hct (In the Diagnosis of Anemia) 1 of 3 Is packed RBC volume Is ratio of RBC volume to volume of whole blood Usually expressed in percentage (42%) or as decimal fraction (.42) Venous and arterial hematocrits closely agree Specimen of choice is EDTA (ethylenediaminetetra acetic acid), oxalate or heparin

Hct (In the Diagnosis of Anemia) 2 of 3 Measurement done by centrifugation or through calculations performed on many automated measurements. Calculated hematocrit is product of MCV and RBC count. Normal ranges are 42-52% in men and 37-47% in women. Normal ranges also vary among age groups, institutions, and geographic locations.

Hct (In the Diagnosis of Anemia) 3 of 3 Problems in measurement of hematocrits include: Incorrect centrifuge calibration Choice of sample site Incorrect ratio of anticoagulant to blood; Improper amount of blood drawn Reading errors

RBC Indices (In the Diagnosis of Anemia) 1 of 2 RBC indices are readily available from the automated hematology counting devices MCV is measured directly or calculated from hematocrit and RBC count; MCH and MCHC are both calculated

RBC Indices (In the Diagnosis of Anemia) 2 of 2 In various anemic states, indices may be altered: Microcytic Anemia: MCV usually 50-80 fL MCH usually 15-25 pg MCHC usually 22-30% Macrocytic Anemia: MCV usually 100-120 fL

Peripheral Blood Smear (In the Diagnosis of Anemia) Very useful in diagnosing and classifying anemias Look for: Neutropenia Thrombocytopenia Hypochromia Size and shape of RBCs Unusual leukocytes (hypersegmentation) Red cell inclusions: basophilic stippling, Howell-Jolly bodies…

Reticulocyte Count (In the Diagnosis of Anemia) Useful in determining response and potential of bone marrow. Reticulocytes are non-nucleated RBCs that still contain RNA. Visualized by staining with supravital dyes, including new methylene blue or brilliant cresyl blue; RNA is precipitated as dye-protein complex. Normal range is 0.5-2.0% of all erythrocytes. If bone marrow responding to anemia, should see increases in retic count. Newborns have higher retic count than adults until second or third week of life.

Bone Marrow (In the Diagnosis of Anemia) Bone marrow aspiration and biopsy are important diagnostic tools in the determination of anemia.

Other Tests (In the Diagnosis of Anemia) Hemoglobin Electrophoresis Antiglobulin Testing Osmotic Fragility Sugar Water Test Ham’s Test RBC Enzymes B12, Fe, TIBC, Folate Levels