| HiCN Test method : Principle of test Whole blood is diluted 1 in 201 in a modified Drabkin’s solution which contains potassium ferricyanide and potassium cyanide. The red cells are haemolyzed and the haemoglobin is oxidized by the ferricyanide to methaemoglobin. This is converted by the cyanide to stable haemiglobincyanide (HiCN). Absorbance of the HiCN solution is read in a spectrophotometer at wavelength 540 nm or in a filter colorimeter using a yellow-green filter. The absorbance obtained is compared with that of a reference HiCN standard solution. Haemoglobin values are obtained from tables prepared from a calibration graph or if using a direct read-out haemoglobin meter, from the digital display Test Requirements : 1. Micropipettes 10ul to 1000ul 2. Test Tubes, 3. Tissue or Cotton,. 4. HiCN Solution ( Drabkin’s solution ) 5. Patient’s Blood 6. Colorimeter or Spectrophotometer Test Procedure: 1. Arrange The Test Tube in Racks. 2. Add 4ml HiCN Solution in Test Tube. 3. Add 20ul (0.02 ml) Patient’s Whole Blood. 4. Incubate at Room Temperature for 4-5 mint. 5. Set The Colorimeter wavelength 540nm at yellow-green filter. 6. Zero the colorimeter with Drabkin’s fluid and read the absorbance of the patient’s sample. 7. if Spectrophotometer then Read The Reading of Hb%. (Factor 35.5) Sahli acid haematin method: This visual comparative method of estimating haemoglobin although still used in some health centres and hospitals is not recommended because of its unacceptable imprecision and inaccuracy. In the Sahli method, 20 l of blood is mixed in a tube containing 0.1 mol/l hydrochloric acid (HC1) which converts the haemoglobin to acid haematin. After 10 minutes (or more), 0.1 mol/lHC1 is added drop by drop, with mixing, until the colour of the solution matches the colour of the glass standard positioned alongside the dilution tube. The concentration of haemoglobin is read from the graduated scale on the dilution tube. Most of the problems associated with the Sahli method are due to the instability of acid haematin, fading of the colour glass standard and difficulty in matching it to the acid haematin solution. Conversion to acid haematin is slow. HbF is not converted to acid haematin and therefore the Sahli method is not suitable for measuring haemoglobin levels in infants up to 3 months. < |
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