Cyanmethemoglobin Method
The cyanmethemoglobin method is another laboratory test used to determine the concentration of hemoglobin in a blood sample. It involves the conversion of hemoglobin to cyanmethemoglobin, which is then measured spectrophotometrically.
Cyanmethemoglobin Method Principle
Cyanmethemoglobin Method is a colorimetric procedure for determining hemoglobin concentration. An aliquot of well mixed whole blood is taken and reacted with a solution of potassium cyanide and potassium ferricyanide (Drabkin’s solution).
The chemical reaction yields a product of stable colour called cyanamethemoglobin. The intensity of the colour is proportional to the hemoglobin concentration and obeys Beer’s law. The hemoglobin in the blood sample is converted to cyanmethemoglobin by the addition of a solution containing potassium ferricyanide and potassium cyanide.
The potassium ferricyanide oxidizes the heme group of hemoglobin to form methemoglobin, while the potassium cyanide reacts with the methemoglobin to form cyanmethemoglobin, which is stable and can be measured using a spectrophotometer. The amount of cyanmethemoglobin produced is proportional to the amount of hemoglobin in the sample.
Requirements for Cyanmethemoglobin Method
- Colorimetre adjusted at 540 nm
- Sahli’s pipette (20 μL capacity)
- Test tubes
- Drabkin’s solution
| Composition | Amount |
|---|---|
| Potassium Cyanide | 50 mg |
| Potassium Ferricyanide | 200 mg |
| Distilled Water | 1000 ml |
Cyanmethemoglobin Method Procedure
- The cyanmethemoglobin method involves the following steps:
- Collect a blood sample from the patient using a venipuncture.
- Transfer a measured volume of the blood sample to a test tube.
- Label the test tubes as test (T) and blank (B)
- Pipette out 5 ml of Drabkin’s solution into both the tubes with the help of automated dispenser or rubber bulb (avoid pipetting by mouth)
- Mix the blood gently
- Draw 20ul blood in the tube labeled as (T) test.
- Mix the contents and wait for 10 minutes
- Take the absorbance of test at 540 nm against blank.
- Take the absorbance of standard directly by taking the standard solution in the cuvette.
- Read the concentration of standard on the vial.
Hemoglobin (g/dl) = Absorbance of test x Concentration of standard
Cyanmethemoglobin Method Results
The results of the cyanmethemoglobin method are reported as the hemoglobin concentration in grams per deciliter (g/dL) of blood. Normal values for hemoglobin concentration vary depending on age, sex, and other factors. In adult males, the normal range is 13.5-17.5 g/dL, while in adult females, the normal range is 12.0-15.5 g/dL.
Uses
The cyanmethemoglobin method is a commonly used laboratory test to measure hemoglobin concentration in the blood. It is used for the diagnosis and management of various medical conditions such as anemia, bleeding disorders, and polycythemia. The test is also used to monitor the response to treatment in patients with these conditions.
Limitations
The cyanmethemoglobin method has some limitations. It requires careful handling of the blood sample to ensure accurate results.
The test may be affected by hemolysis, lipemia, or icterus, which can interfere with the accuracy of the results. In addition, the cyanmethemoglobin method may not detect certain types of hemoglobin variants, which can result in false-negative results.
Finally, the test may be affected by other factors such as altitude, smoking, and pregnancy, which can affect the hemoglobin concentration in the blood.
Clinical Manifestations of Cyanmethemoglobin Method
The cyanmethemoglobin method is used to measure the concentration of hemoglobin in the blood, which is important for the diagnosis and management of various medical conditions such as anemia, bleeding disorders, and polycythemia.
The test is also used to monitor the response to treatment in patients with these conditions.
