BIOCHEMİCAL EVALUATION OF ANEMIA

Prof.Dr.Arzu SEVEN

Biochemical evaluation of anemia

• Hemolytic disorders resulting from erythrocytic enzyme abnormalities:

• a)enzymes of Emden-Meyerhof Pathway of anaerobic glycolysis

-hexokinase -glucose phosphate isomerase -phosphofructokinase -triosephosphate isomerase -phosphoglycerate kinase -pyruvate kinase

• b)hexose monophosphate pathway

-transketolase

-glucose 6-phosphate dehydrogenase(G6PD)

• c)glutathione pathway

-GSH peroxidase

-GSH synthetase

• d)purine pyrimidine metabolism

-adenosine triphosphatase

-adenosine deaminase

-pyrimidine-5'-nucleotidase

Pyruvate kinase deficiency

• Most common

• Autosomal recessive

• Mild severe

• İnability to synthesize ATP for RBC metabolism, ion gradients γ cell shape

• 2,3 BPG -O2 affinity

-O2 delivery to muscle γ fetus

G6PD deficiency

• Genetic

• Mutation

• Common in Mediterenean γ Africo_Carribbean origins

• NADPH

• GSH can not be regenerated from GSSG

• GSSG , H2O2 , radicals

• Oxidative challenge: -oxidants (antimalarial primaquine,

aspirin, sulfonamids) -severe infections -fava beans• Primaquine sensitive hemolytic anemia • Peroxidation of lipids in RBC membrane RBC lysis

Iron deficiency anemia

• A common nutritional problem seen especially in menstruating γ pregnant women

• ♂ 1 mg iron/day

• Mensruating ♀ ~ 2mg iron/day

• Pregnant ♀ ~3mg iron/day

Megaloblastic anemia

• Inadequate folate intake

impaired absorption

impaired metabolism

increased demand (pregnancy, lactation)

folate deficiency methionine

nucleic acid

• Enlarge blast cells in bone marrow • Macrocytic RBC with fragile membranes

tendency to hemolyze (macrocytic anemia) • Folate supplementation (400 mg/day)

during periconception period (4 weeks before γ 8 weeks after conception) prevents neural tube defects in spina bifida and hyperhomocysteinemia)

Pernicious anemia

• PA is a conditioned nutritional deficiency of cobalamin by failure of gastric mucosa to secrete IF

• Inadequate intake of vit B12 extremely rare• Defective production of IF most common• Genetically determined, but not

manifested until late in life

• vit B12 deficiency folate deficiency• IF deficiency in the stomach prevents

vit B12 absorption in terminal ileum• gastric surgery surgical removal of ileum IF (Crohn's disease)

vegans vit B12

• Gastrointestinal symptoms

(episodic abdominal pain, constipation

γ diarrhea)

• Atrophic gastritis

• Immune abnormalities:

antiparietal cell antibodies

anti-IF antibodies

• Liver disease associated with alcoholism may lead to folate_deficiency megalosblastic anemia

• During the investigation of the cause of megaloblastic anemia, folate must be given together with B12 vit.(to prevent neuropathy)

Correlation of vit.B12 and folate levels with clinical status:three laboratory tests need to separate four clinical situations

Clinical situation

Serum vit.B12 (pg/mL)

Serum folate

(ng/mL)

Red cell folate

(ng/Ml)

normal Normal

(200-900)

Normal(5-16),intermediate(3-5), or low(<3)

Normal(>150)

Vit.B12 deficiency

Low(<100) Normal(5-6) or high(>16)

Low(<150)

Folic acid deficiency

normal low low

Deficiency of both

low low low

Methods for the determination of vitamin B12 and Folic acid

• Microbial assay

• Competitive protein binding assay

• Immunometric assay

Indirect methods for assessment of vitamin B12

deficiency• Methylmalonic acid assay

• Measurement of homocysteine

• Deoxyuridine suppression test

• Vit.B12 absorption (Schilling) test

• Tests for intrinsic factor blocking antibodies

• Because vit.B12 is needed for the conversion of methylmalonic acid to succinic acid , patients deficient in vit.B12 excrete excess amounts of methylmalonic acid in urine

• Homocysteine is increased in the plasma of patients who are deficient in vit.B12 because their cells can not metabolise homocysteine to methionine at a normal rate

• The increase in plasma homocysteine may precede the typical signs of macrocytic anemia and decreased cobalamin

• Schilling test permits differentiation of causes of vit B12 deficiency (pernicious anemia or intestinal malabsorption)