MLAB 2401: Clinical Chemistry Keri Brophy-Martinez

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MLAB 2401 Clinical ChemistryKeri Brophy-Martinez

• Chapter 5 Assessment of Iron, Porphyrins and
  Others

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Specimen Requirements Iron Studies

• Serum without anticoagulant
• Plasma with heparin ( check product insert)
• Oxalate, citrate or EDTA binds Fe ions, so they
  are unacceptable
• Early morning sample preferred due to diurnal
  variation
• No hemolysis

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Iron Study/Profiles

• Three Components
• Total Iron ( serum )
• TIBC
• Iron Saturation ( Fe Sat )
• The Iron Saturation is a measurement of how
  full transferrin is

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Assessing Iron Levels and Forms

• Directly measured
• Iron
• Transferrin
• Beta globulin formed in the liver
• Measured by the amount of iron it can bind
• Ferritin
• Best diagnostic test for IDA
• Acute phase reactant

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Assessing Iron Levels and Forms

• Indirect measure
• TIBC (Total iron-binding capacity)
• Measures the total amount of iron that
  apotransferrin can bind
• Can be expressed as a percentage(percent
  saturation)
• Ratio of serum iron to TIBC
• Increased
• Late pregnancy
• IDA
• Following hemorrhage
• Following destruction of liver cells
• Decreased
• Decreased synthesis of transferrin
• Increased loss of urine proteins

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Test Methodologies Iron

• Colorimetric Procedure
• Separate Fe from transferrin with a strong acid
• Iron is reduced from ferrous(Fe3) to
  ferric(Fe2) state
• Addition of a chromogen creates a colored
  compound
• Measurement of colored product by
  spectrophotometry

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Iron Reference Ranges

• Diurnal variation
• Men 65-165 µg/dL
• Women 45-160 µg/dL

• Decreased Levels
• Decreased intake
• Increased need
• Increased loss
• Increased Levels
• Increased absorption
• Hemolytic anemia
• Lead poisoning
• Pernicious anemia
• Megaloblastic anemia
• Hepatitis

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Test MethodologiesTIBC

• Pre-treatment and Colorimetric Method
• Add Fe3 to saturate binding sites on transferrin
• MgCO3 is added to remove unbound Fe3
• Mixture is centrifuged and the supernatant tested
  using the serum iron methodology

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Reference Ranges

• Transferrin
• 200-360 mg/dL
• Ferritin
• Male 20-250 ng/mL
• Female 10-120 ng/mL
• TIBC
• 250-425 µg/dL
• saturation
• 15-55

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Test Methodology Hemoglobin

• Electrophoresis
• Discussed in separate unit

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Test Methodology Porphyrins

• Screening tests
• Urinary PBG
• Urinary ALA
• Urinayr porphyrins
• Quantitative Assays
• URO
• PROTO
• COPRO
• Serve to classify porphyrias

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Lab Methods

• Watson-Schwartz for Urinary PBG( porphobilinogen)
• Screen for acute intermittent porphyria
• Specimen
• Qualitative fresh morning urine
• Quantitative 24 hour collection
• Reference Range
• lt2 mg/daily

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Watson-Schwartz

• Principle
• PBG Ehrlichs reagent results in a red-orange
  chromogen
• Interferences
• Urobilinogen
• indole

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Lab Methods HgbA1c

• Electrophoresis
• Enzymatic Assays
• HPLC
• Goal is to separate hemoglobin forms within a
  column. Then, glycated versus total hemoglobin
  can be measured spectrophotometrically
• Specimen requirements
• EDTA whole blood
• Can be non-fasting
• Reference range
• 4.0-6.0

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Lab Methods Myoglobin

• Procedures incorporate the binding of specific
  antibodies to myoglobin with a resulting chemical
  or physical change that can be measured and
  correlated to myoglobin concentration
• Specimen requirements
• Usually plasma ( check product insert)

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Specimen Requirements Lead

• Whole blood
• Why? Circulating lead found in the RBC
• Venous sample preferred but capillary sample can
  be used ( must confirm positive on capillary)
• Royal blue top with EDTA anticoagulant
• Lead-free containers
• Urine

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Lab Method Lead

• Test methodologies
• AAS
• Anodic stripping voltammetry
• Reference Ranges in blood
• Childrenlt 10 µg/dL