Sahli’s Method of Hemoglobin Estimation: Introduction, Principle, Procedure, Result- Interpretation, and Keynotes

Introduction of Sahli’s Method of Hemoglobin Estimation

Sahli’s Method of Hemoglobin Estimation is also called the acid hematin method of hemoglobin estimation and the method is cheap, with no need for an electrical supply and even there is no need for technical expertise to perform the test.

Principle

Blood is mixed with an acid solution and the hemoglobin of the blood is converted to brown-colored acid hematin. This is then diluted with distilled water till the brown color matches that of the brown glass standard. The value of hemoglobin is noted directly from the scale.

Test Requirements

Sahli’s Hemoglobinometer Kit contains-

• Sahli’s graduated hemoglobin tube (g% 2-24 and 10 -140 %)
• Comparator
• Sahli’s pipette or hemoglobin pipette
• Stirrer ( a thin glass rod)
• Dropper
• Wash brush

Extra we need-

• N/10 or 0.1 N hydrochloric acid
• Distilled water
• Gloves
• Spirit swab
• Lancet
• Waste bin (puncture proof)
• O.5% Hypochlorite solution (bleach)

Procedure

1. First, clean your hands and wears gloves.
2. Fill the hemoglobin (Hb) tube with 0.1 N HCl up to 2 gm with the dropper and place it in the Hb Meter
3. Clean the tip of the person’s ring finger with a spirit swab.
4. Prick the finger with a lancet and discards the first blood drop.
5. Allow a large blood drop to form on the fingertip and suck it with Hb pipette up to the 20 cm mark. Takes care that air entry is prevented while sucking the blood.
6. Wipe the tip of the pipette and transfers the  blood to the Hb tube containing 0.1 N HCl
7. Wipe the tip of the pipette and transfers the  blood to the Hb tube containing 0.1 N HCl
8. Leave the solution in a Hb tube for 10 minutes
9. After 10 minutes, dilute the acid by adding distilled water drop-by-drop and mix it with a stirrer
10. Note down the reading (lower meniscus) when the color of the solution exactly matches that of the comparators on both sides of the Hb Meter.

Result Interpretation

After matching the color of both the test and comparator, read the lower meniscus of the solution and express the result of hemoglobin content as gm/dl or g%.

Normal Range of Hemoglobin

• Women, 12.0- 15.5 gm/dl
• Men, 13.5 -17.5 gm/dl

Keynotes

• Demerits of Sahli’s method of Haemoglobin estimation are as follows-

1. Carboxyhemoglobin, methemoglobin, and sulfhemoglobin (stable, green-pigmented molecule) are not converted to acid hematin.
2. The color of brown glass standard fades with time.

• The cyanmethemoglobin method is the globally recommended method.
• Other than Sahli’s method or visual method/color comparison method for hemoglobin are specific gravity methods (commonly used for screening blood donors), a spectrophotometric method, a Gasometric method, and automation.
• Other than Sahli’s method, the Tallqvist chart and WHO hemoglobin color scale are also visual methods of hemoglobin estimation.
• Rinse the Hb tube 2-3 times with 0.1 N HCl and disposes of the used lancet in a puncture-proof container. waste bin.
• Drabkin’s solution is used in the cyanmethemoglobin method.
• Hemoglobin is tested for the following purposes-

1. To find out the presence and severity of anemia
2. Screening for polycythemia
3. To assess response to a specific therapy in anemia.
4. Estimation of red cell indices (MCV. MCH, MCHC)
5. Selection of blood donors in the blood donation program.