Clinical Significance
A decrease in hemoglobin below normal range is an indication of anemia. An increase in hemoglobin occurs in hemoconcentration due to loss of body fluid in severe diarrhea and vomiting. High concentration values are also observed in congenital heart disease (due to reduced oxygen supply) in emphysema and also in polycythemia. Hemoglobin concentration drops during pregnancy due to hemodilution.
Normal values
- man : 13-18 Hb, g/dl
- Women: 12-16.5 Hb, g/dl
- Children (up to 1 year): 11.0-13.0 Hb, g/dl
- Children (10-12 years): 11.5-14.5 Hb, g/dl
- Infants (full term cord blood): 13.5-19.5 Hb, g/dl
Method:
Sahli (acid hematin) method
Principle
When blood is added to 0.1 N hydrochloric acid, hemoglobin is converted to brown colored acid hematin. The resulting color after dilution is compared with standard brown glass reference blocks of a Sahli hemoglobinometer.
Specimen
Capillary blood or thoroughly mixed anticoagulated (EDTA or double oxalated) venous blood. The specimen need not be a fasting sample. When blood is stored in the refrigerator (2°C-8°C), hemoglobin remains unchanged provided that the blood does not become infected (as shown by turbidity or discoloration).
Requirements
1. Sahli hemoglobinometer: It consists of
a) A standard brown glass mounted on a comparator
b) A graduated tube (Hellige tube)
c) Hb pipette (0.02 ml)
Note
The graduations on currently used Hellige tube gives 14.5 g as 100%. These are square tubes with graduations in percent on one side and grams per 100 ml (dl) on the other side.
2 0.1N hydrochloric acid
3 Distilled water
4 Pasteur pipettes
Procedure
1 By using a Pasteur pipette add 0.1 N hydrochloric acid in the tube up to the lowest mark (20% mark).
2 Draw blood up to 20 µl mark in the Hb pipette. Adjust the blood column, carefully without bubbles. Wipe excess of the blood on the sides of the pipette by using a dry piece of cotton (or gauze).
3 Transfer blood to the acid in the graduated tube, rinse the pipette well, mix the reaction mixture and allow the tube to stand for at least 10 minutes.
4 Dilute the solution with distilled water by adding few drops at a time carefully and by mixing the reaction mixture, until the color matches with the glass plate in the comparator.
5 The matching should be done only against nat- ural light. The level of the fluid is noted at its lower meniscus and the reading corresponding to this level on the scale is recorded (blood hemoglobin, g/dl).
Additional Information
1 Methemoglobin, carboxyhemoglobin and sulfhemoglobin are not converted to acid hematin by 0.1 N hydrochloric acid.
2 This method is useful for places where a photometer is not available.
3 It can give an error up to 1 g/dl.
Precaution
Immediately after use rinse the Hb pipette by using tap water in a beaker. This prevents blocking of the pipette.
