19 Cell Washing: Manual Method
Principle
The removal of unbound human serum proteins is necessary before the addition of antihuman globulin (AHG) to both direct and indirect Antiglobulin tests. Washing the red cells several times with isotonic saline removes unbound proteins.
Related Policies
This procedure applies to all tests that require the addition of AHG to the test.
Procedure
- Label tubes with patient name, MRN and test or reagent identification.
- Complete the procedure for each test as described in the particular SOP up until the point that washing is required.
- Prior to washing, suspend the red cells. Fill each tube ¾ full with isotonic saline; do not put the tip of the saline bottle into tube (avoid contamination).
- Centrifuge the tube(s) on high for 1 minute. Decant (“dump”) the supernatant fluid off of the cell button into a dirty sink or biohazardous waste bucket.
- Repeat steps 3 and 4 for a total of 4 times.
- After the last wash, decant (“dump”) the saline completely, then blot while continuing to hold the tube upside down so the cell button is dry.
- Complete the test procedure as described in the relevant SOP.
Notes
- Loss or hemolysis of the red blood cells from improper washing may result in false results.
- Failure to adequately wash can cause false-negative reactions due to neutralization of the AHG reagent by unbound globulins.
- False-negative results may occur if the washing process is delayed or interrupted.