RBCs Flashcards
erythrocyte components of a CBC
- Red Blood Cells (RBC) –> erythrocytes
- Hemoglobin(Hgb)
- Hematocrit (Hct)
- Red Blood Cell Indices
hemoglobin
o Iron containing protein in RBCs that carries O2 from the lungs to the body’s tissues and CO2 back from the tissues to the lungs
o Composed of 2 subunits: beta globin and alpha globin
hematocrit
o Packed cell volume (the ratio of RBCs to total blood volume)
o Hint: Hemoglobin x 3 = estimate of hematocrit
mean corpuscular volume (MCV)
average size in volume of a RBC
mean corpuscular hemoglobin (MCH)
gives you the average amount of hemoglobin that is in each blood cell
mean corpuscular hemoglobin concentration (MCHC)
gives you the average weight of the hemoglobin based on the volume of RBCs
RBC Distribution Width (RDW)
this is a measurement that reflects the range of size in volume of RBCs; may be elevated in conditions like iron deficiency anemia, macrocytic anemia
Erythropoiesis
- Aka hematopoiesis
- Process of maturation of RBCs from the stem cell phase to full maturity
- A functioning erythropoiesis feedback loop allows for the number of RBCs to maintain stable levels
- When the body is in a diseased state, blood cells that are lost are replaced so sufficient oxygen levels are maintained
- Erythropoietin levels in circulation increase as the levels of RBCs decrease
stages of maturation
**RBC is higher first 2 weeks after birth and then a dip from 6-12 months
**Prior to that the infant’s iron stores are reflecting the mother’s nutrition from the last trimester of pregnancy
**Definition of anemia in kids is a hemoglobin of less than the 5th percentile or a hemoglobin of less than 2 SD below the mean population for the same gender and age
anemia
- The condition of having a lower-than-normal number of RBCs or quantity of hemoglobin (reduced RBC mass)
- Anemia results in the diminished capacity of the blood to carry oxygen and often hypovolemia, resulting in:
o Fatigue, weakness, pallor, palpitations, SOB, dizziness, chest pain, cold hand and feet
o S/s hyperdynamic state, decreased CO
causes of anemia
- Acute blood loss – overt, occult
- Hemolytic Anemia
- Anemia of Chronic Disease –> most common in pts with chronic kidney disease, hemodialysis, or heart failure
- Malabsorption–> iron deficiency anemia, can be an issue in Celiac disease, H. pylori
- Nutritional–>vegetarians are more likely to get anemias
- Drug Induced Anemia
o Oxidative stress–> hemolysis
o Methemoglobinemia
o Hemolytic anemia - Lead Poisoning
lead poisoning
- Lead molecules are blocking iron absorption–> iron deficiency anemia
- Perform lead exposure risk assessment at the following well-child visits: 6, 9, 12, 18, 24 mos, and 3, 4, 5 and 6 years of age.
- If risk assessment is positive check blood lead level
- Per AAP and CDC, universal screens or blood lead level tests are no longer recommended except for high prevalence areas with increased risk factors (i.e. older housing)
Definition of Anemia in Children: Hemoglobin
*Does vary by age and you have that dip from 6-12 months due to the mother’s iron stores
*At 12 months or older, if there is a Hgb of less than 11 that is considered anemic
screening in children
- AAP recommends screening at 9 to 12 months of age
- High risk groups should have more intensive screening premature infants, low birth weight infants
anemia screening in adults
- Women during pregnancy??
o USPSTF: Grade I (insufficient evidence) for routine screening of asymptomatic pregnant women
o ACOG: screen at 1st prenatal visit
o UTD: repeat at week 24-28 - No routine screening in asymptomatic adults
o Any individual with risk factors, symptoms or findings of IDA should be tested:
Premenopausal women (heavy periods, prior pregnancies)
Conditions with associated risk of blood loss or iron malabsorption
o If CBC done for other reasons, review results including MCV - If IDA diagnosed in men or postmenopausal women – should have GI endoscopic testing
Classification of Anemia
- Morphologic
o Size
Macrocytic–> abnormally large RBCs
Microcytic –> abnormally small RBCs
Normocytic–> normal RBCs
o Amount of hemoglobin (color) - Pathologic
o Blood loss
o Hemolytic
o Impaired production/underproduction
mean corpuscular volume (MCV): size
- Normocytic: RBCs size and volume is normal
- Microcytic: MCV is below normal range–> RBC size is below normal (small)
- Macrocytic: MCV above normal range–> RBC size is above normal (large)
mean corpuscular hemoglobin (MCH)
- Average amount of hemoglobin within an RBC
- Normal adult value: 27.0-33.0 pg/cell
- Average percentage of hemoglobin within a single RBC
- Normal adult value: 31.0-36.0 g/dL
- Low MCH indicates that the amount of hemoglobin per cell is abnormally decreased; often seen with iron deficiency anemia or thalassemia
RBC Distribution Width (RDW)
- Indication of variation in RBC size
- Normal adult value: 11-15%
- Normally RBCs are the same size and shape
- High RDW implies that there is a large variation in RBC size
- RDW might be elevated in condition such as iron deficiency anemia, myoplastic syndromes, hemoglobinopathies, pts who have recently had a transfusion
elevated RDW
- Variation in size: anisocytosis
Reticulocytes
- Newly produced, immature red blood cells
- Reflection of recent bone marrow activity
- An increased number of reticulocytes may be seen in response to bleeding or hemolysis
- Abnomally decreased or increased Retic Count suggest hypo- or hyperproliferative anemia
mechanisms of anemia
- Blood loss anemia—> trauma, acute GI bleed, PPH; greater than 100,000
- Hemolytic anemia–> greater than 100,000; due to premature destruction of RBCs
- Hypoproliferative anemia—> hallmark is a low reticulocyte count of less than 75,000
blood loss anemia
- Ask about: dizziness, falls, blood thinners, hematemesis, hematuria, melena, rectal bleeding, vaginal bleeding, menses, hemoptysis, hemorrhoids
- Check for: hypotension/orthostatic hypotension, ecchymosis, tachycardia, trauma
- Typical etiology: GI bleed
o Can be hemorrhagic or slow, occult or overt - Slow GI bleeds present as Iron Deficiency Anemia
- Monitor hematocrit
- Acute vs. Chronic
o Patients can tolerate lower HCT in chronic anemia
hemolytic anemia
premature destruction of RBCs
hemolytic anemia: can be congential or acquired
Congenital
o G6PD deficiency
o Sickle Cell
o Thalassemia
o Hereditary spherocytosis
Acquired
o Autoimmune (secondary to autoimmune disorders, malignancy, drugs, transfusion reactions), microangiopathy, infection
hemolytic anemia: intravascular vs extravascular hemolysis
o Intravascular: destruction of RBCs in the circulation (less common) caused by mechanical trauma and infectious agents
o Extravascular: removal and destruction of RBCs by macrophages of the spleen and liver
s/s hemolytic anemia
o Typical signs of anemia +
o Dark urine
o +/- back pain
o Pale or jaundiced skin
o Lymphadenopathy or hepatic splenomegaly
diagnostic test findings: hemolytic anemia
o Characteristic feature = normocytic with a marked reticulocytosis
o Sometimes macrocytic due to increased volume of reticuloctyes
o Increased unconjugated bilirubin and lactic dehyrogenase – released into the blood stream when RBCs are destroyed
o Decreased Haptoglobin – binds to liberated hemoglobin and is quickly cleared by the liver
oHyperproliferative
Appropriate response of the bone marrow
Seen in blood loss and hemolytic anemias and following replacement in deficiency anemias
Normal in pregnancy
o Hypoproliferative
Bone marrow is unable to respond
Seen in nutritional deficiencies, aplastic anemia, radiation, bone marrow failure, severe kidney disease, alcoholism
Hypoproliferative Anemia
- Bone marrow is unable to adequately produce RBCs (impaired/underproduction)
Hypoproliferative Anemia: hallmark
- Hallmark is low reticulocyte count
Hypoproliferative Anemia
- Check the MCV to determine etiology
Microcytic anemias
**o Iron deficiency
o Thalassemia
o Lead exposure
** Normocytic anemias
**o Anemia of chronic dz
o Early iron deficiency
o Bleeding, hemolytic
o Bone marrow suppression
o Mixed macro & microcytic anemia
** Macrocytic anemias
o Megaloblastic anemia
**Folate deficiency
Vitamin B12 deficiency
Antimetabolite drugs (chemo)
**o Non-megaloblastic
** Etoh
Liver dz
Hypothyroidism
Myelodysplasia
Microytic Anemia
- Most commonly iron deficiency anemia (IDA)
o Microcytic and hypochromic - Check iron studies
o Start with Ferritin - major iron storage protein
o Low ferritin rules in IDA but normal levels do not rule it out
Ferritin is an acute phase reactant – can be elevated with inflammatory disease, infection, neoplasms
o Normal ferritin level: add TIBC, total iron and transferrin saturation
o Elevated ferritin level: rules out IDA
iron studies
- Transferrin: serum iron transport protein – brings iron to the bone marrow
o Can be measured directly with a transferrin level, however more commonly measured by looking at TIBC
Total Iron Binding Capacity: Measures the amount of transferrin available to bind to iron
Increased TIBC means you are not carrying as much iron as you could - Serum iron level – measures the total amount of iron in the blood – nearly all of which is bound to transferrin
- Transferrin saturation
o Serum iron x100%/TIBC - Normal reference ranges:
o Serum iron: 60–170 μg/dL (10–30 μmol/L)
o Total iron-binding capacity: 240–450 μg/dL
o Transferrin saturation: 15–50% (males), 12–45% (females)
hemocrhomatosis
- Genetic disorder that disrupts the body’s regulation of iron
- Most common in white populations of northern European origin
- Often asymptomatic
- Symptoms may include
o weakness,
o lethargy,
o arthralgias,
o impotence
thalassemia
- Inherited blood disorder characterized by abnormal hemoglobin production
- 2 main types
o Alpha – Deletion of some or all of the HBA genes cause reduced levels of alpha globulin
o Beta – mutations in the HBB gene cause reduced levels of beta globulin
** Hypochromic, microcytic anemia
** Certain ancestries increase risk
o African American, Mediterranean, Southeast Asian
Beta Thalassemia
- Heterozygous – carrier and have Beta thalassemia trait
o May have mild anemia with microcytosis - Homozygous – Beta thalassemia major (Cooley anemia)
o Life threatening, requires frequent transfusions
Alpha Thalassemia
- 2 genes (HBA1 and HBA2), each with 2 copies
- Degree of condition related to how many gene copies are lost and in which combination
microcytic with increased RDW=
iron deficiency anemia
microcytic with normal RDW=
thalassemia
Anemia of Chronic Disease
*** Typically normocytic, normochromic
**o May be microcytic – don’t mistake for IDA!
o Low reticulocyte count, normal/elevated ferritin, low/normal serum iron
* Think about in patients which chronic immune or infectious processes or neoplasm
o The chronic inflammation and immune system stimulation produces cytokines that alter the bodies ability to store and transport iron
* Chronic renal disease – decreased production of erythropoeitin leads to decreased production of RBCs
Megaloblastic Anemia
- Macrocytosis + presence of hypersegmented neutrophils and macroovalocytes on peripheral smear
- Vitamin B12 or Folate deficiency
o Essential for DNA synthesis
o Related to:
Inadequate intake - Folate (lack of fresh veggies)
- B12 (lack of meat and dairy)
Increased requirement – pregnancy, infancy, chronic inflammatory diseases, malignancies
Medications
Malabsorption - Folate: small bowel disease
- B12: pernicious anemia, gastrectomy, chrohn’s, ileal resection
- Check B12 and Folate levels
o B12 deficiency:
CBC can be normal for a long time
Don’t miss diagnosis – can lead to: - Adults: irreversible neuro sx
- Kids: growth retardation, seizures
o B12 levels can be difficult to interpret:
B12 “falsely” low: pregnancy, OCP use, folate deficiency
B12 “falsely” normal: liver disease, bacterial overgrowth syndromes
B12 “falsely” high: Etoh, liver disease, cancer
o B12 <150 diagnostic - If suspect B12 deficiency but levels don’t support: check MMA and homocysteine
- Methylmalonic Acid (MMA)
o Vitamin B12 promotes the conversion of methylmalonyl CoA (a form of MMA) to succinyl Coenzyme A.
o If there is not enough B12 available, then the MMA concentration begins to rise, resulting in an increase of MMA in the blood and urine.
o Increased MMA = decreased B12
o Can also be elevated in chronic kidney disease
o Levels >1.0 are highly indicative of B12 deficiency - Homocysteine
o Amino acid that requires B6, B12 and folate for its metabolism to methionine
o Increased levels of homocysteine can indicate B12 or folate deficiency
o Also plays a role in inflammation – marker in MI, stroke, blood clot
o Nonspecific
folate deficiency
- Serum levels vary greatly based on diet
- Better to check RBC folate level
- Will see elevated Homocysteine but normal MMA with folate deficiency
pernicious anemia
- B12 deficiency due to lack of intrinsic factor related to autoimmune destruction of parietal cells or gastrectomy
- Suspect in persons with B12 deficiency and other autoimmune disorders
- Schilling Test – no longer available in the US
- Test for anti-intrinsic factor antibodies
what if the Hgb and Hct are elevated?
- Polycythemia vera
o Myeloproliferative disease
Hyperviscosity thrombosis
Tx: low dose aspirin and therapeutic phlebotomy - Secondary Polycythemia
o Chronic hypoxia leads to increased erythropoietin production
OSA
Smoking
Altitude
Chronic pulmonary disease
Erythropoeitin secreting tumors
