10 Questions
What is the wavelength at which the absorbance of an aliquot of HiCN standard is measured?
The same wavelength as whole blood samples
What is the purpose of the Hemoglobin Standard solution?
To prepare a calibration curve for hemoglobin measurement
What is the advantage of using the Cyanmethemoglobin Standard solution?
It is a stable standard solution that can be used to calibrate instruments
What is the formula used to calculate hemoglobin levels?
Hb (g/dl) = At Cst DF / Ast 1000
What is the reference range for hemoglobin levels in adult females?
11-16g/dl
What is a source of error when measuring hemoglobin photometrically?
Not measuring the correct volume of blood due to poor technique
What is the purpose of Drabkin's solution?
To dilute whole blood samples for measurement
What is the advantage of using Drabkin's solution?
It is readily available and stable
What is the hemoglobin level of the Cyanmethemoglobin Standard solution?
18g/dl
Why should local reference values be established?
Because reference values vary with age, sex, physiologic condition, and altitude
Study Notes
Hemoglobin Measurement Methods
- Sahli-Hellige method: not recommended due to its imprecise and inaccurate results
- Principle: 20μL of blood is mixed with 0.1mol/L HCl, which converts hemoglobin to acid hematin, and the color is compared to a standard
- Procedure: involves mixing blood with HCl, adding drops of HCl or water until the color matches the standard, and reading the concentration from the graduated scale
Spectrophotometric Methods
- Cyanmethemoglobin method: ICSH recommended reference method
- Principle: blood is diluted in Drabkin's solution, which converts hemoglobin to hemiglobin cyanide, and the absorbance is measured at 540nm
- Reagent: Drabkin's solution contains potassium ferricyanide, potassium cyanide, and potassium dihydrogen phosphate
- Procedure: involves mixing blood with Drabkin's solution, allowing it to stand, and measuring the absorbance at 540nm
- Calculation: Hb (g/dl) = At × Cst × DF / Ast × 1000
Calibration
- Hemoglobin Standard is a dry vial containing standardized methemoglobin
- Reconstituting the standard yields the Cyanmethemoglobin Standard solution
- Calibration curve is prepared using dilutions of the standard solution
Reference Range
- Adult males: 13-18g/dl
- Adult females: 11-16g/dl
- Newborns: 14-23g/dl
- Note: reference values vary with age, sex, physiologic condition, altitude, etc.
Advantages of Cyanmethemoglobin Method
- Stable Hemiglobincyanide standard available
- Convenient method
- Readily available and stable standard solution
- All forms of hemoglobin except sulfhemoglobin are readily converted to HiCN
Sources of Error
- Not measuring the correct volume of blood due to poor technique or using a wet or chipped pipet
- Not mixing the sample sufficiently when using anticoagulated venous blood
Learn about different methods for measuring hemoglobin levels, including Sahli-Hellige and spectrophotometric methods.
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