Value:
When reagents are available, this test should be performed in preference to the sickle cell slide test because it provides information about the different sickle cell disorders. In areas where both HbS
and HbD occur this test can be used to differentiate sickle cell anaemia (HbSS) from HbSD sickle cell disease.
Principle of the test
Blood is mixed in a phosphate buffer-saponin solution containing sodium dithionite and filtered. In its deoxygenated
form, HbS is insoluble. HbSS is indicated by a red precipitate on the filter paper with a pale yellow filtrate. Other forms of
haemoglobin are soluble when in a reduced state.
Reagents
● Phosphate buffer-saponin pH 7.1
Store at 2–8 C. Renew every 3 months or if it
becomes turbid.
● Sodium dithionite powder.
Making a working reagent:
– Measure 20 ml of buffer-saponin solution.
– Add 0.2 g sodium dithionite and mix gently until the chemical is dissolved.
Note: The working reagent is not stable. It can be used only on the day it is prepared.
See also:
Lablink 
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