Hematology hemoglobin and RBC indices

Hemoglobin

4 globular subunits (each with heme group) - one group = 1 o2

Hb dimers

2 unlike chains (one alpha, one non-alpha)

Fetal Hb

a2y2 (2 alpha 2 gamma) → 90-95% blood before birth

Adult (HBA)

a2b2 (95% blood)

Heme

iron must be in the Fe2+ state Ferrous iron has 6e- pairs/bind sites (4 bind to nitrogen, 1 to histidine, 1 to oxygen) → synthesized in mitochondria

Deoxyhemoglobin

T state with low o2 affinity, stabilized by intersubunit salt bridges, stable at higher temperatures

Oxyhemoglobin

R relaxed state, high o2 affinity, salt bridges gone, lower temps

Allosteric effects

o2 affinity decreases in response to allosteric effects (ph, co2, 2,3 BPG) → allosteric effectors form salt bridges for T state

Cooperative o2 binding

o2 binding leads to higher affinity of other o2 binding → break salt bridge →hb goes T to R state → 2,3 BPG expelled

CO2 transport

most co2 as carbonic acid (in rbc) → some binds to n-terminal of hb (carbaminohemoglobin), some in plasma

Hemosiderinuria

presence of iron-containing pigment (hemosiderin) in urine (chronic hemolysis)

Hemoglobinuria

Presence of free hemoglobin in the urine

Methemoglobin

Hb iron in ferric state cannot combine with o2 → CHOCOLATE BLOOD

Sulfhemoglobin

Sulfur combines with hb (GREEN BLOOD)

Carboxyhemoglobin

CO carbon monozide ocmbines with Hb (CHERRY RED blood)

RBC count

amount of RBC/unit volume of blood (RI$ 4.4-5)

Hematocrit

RI= 36-53%

Hb

RI = 12-17.4

RBC indices

classify RBC by size and Hb content (RBC, Hct, Hb)

Mean cell volume

MCV average volume of individual rbc (RI = 80-100 fL) [hct%/#RBCs * 10] HIGH MCV = larger cells (macrocytic)

Macrocytic

high MCV

Microcytic

low MCV

Normocytic

normal MCV (same size as lymphocyte)

Mean corpuscular Hb (MCH)

weight if hb in RBC (RI = 28-34) NOT ACCOUNT FOR SIZE OF CELL + linear relationship with MCV (small cells = low hb) [ hb/rbc * 10]

Mean cell HB Concentration MCHC

accounts for cell size (RI = 32-36 g/dL) [hb/hct *100]

Normochromic

central pallor about ⅓ cell

Hypochromic

central pallor more than ⅓ (LOW hb)

Hyperchromic

central pallor less than ⅓ (high Hb proportionally) IN SPHEROCYTES

Red Cell Distribution width RDW

MCV average of rbs volume (RI = 11.5-14.5%) GREATER = anisocytosis [1SD/MCV * 100]

Anisocytosis

lots of variation in cells (RDW>14.5%) → skew MCV values

Reticulocyte count

indicate bone marrow activity and RBC production (esp in anemia)

Relative Reticulocyte count RRC

RI = 0.5 - 2.0% [#reticulocytes/#RBCs * 100]

Absolute reticulocyte count

BETTER INDICATOR RI = 25 - 75 mcL [RBC count * RRC(%)/100] higher in anemic patients

Anemic results

high BM activity and higher # RBCS

Low reticulocyte counts

BM failure, low iron, liver disease

High reticulocytes count

hemolysis, hemorrhage. Leukemia, sickle cell anemia

Platelet count PLT

RI 150 - 400 mcL

WBC count and differential

RI= 4.5 -11 mcL (total WBC high = leukocytosis, low = leukemia)

Serum Iron

RI = 50 -180 mcg/dL

Total iron binding capacity TIBC

RI = 250 - 450 microgram of iron/deciL

Transferrin saturation

Indicates available iron for erythropoiesis RI = 16-50%

ZPP

absence of iron → zinc is incorporated into the protoporphyrin ring, forming ZPP (RI = 1 - 45 mcg/dL)

Folate

RI = 4-20 mg/L (needed with vitamin b1 to make thymine → dna → THF active form)

Cobalamin

RI = 150 - 400 pg/mL (Cofactor required for DNA synthesis)