Coombs

COOMBS TEST

Indirect Coombs test (Indirect Antiglobulin test):
This test is performed to detect presence of Rh-antibodies or other antibodies in patients serum in case of the following: 1. Tocheck whether an Rh-negative women (married to Rhpositive husband) has developed Anti Rh-antibodies
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2. Anti D may be produced in the blood of any Rh-negative person by exposure to D antigen by 

Transfusion of Rh positive blood Pregnancy, if infant is Rh positive (if father is Rh-positive) Abortion of Rh-positive fetus.

Requirements:
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Test tubes: (10x75 mm) Pasteur pipettesIncubator Centrifuge

Specimen: Serum (need not be fasting) Reagents: 1. Antihuman serum 2. Anti-D serum Additional Requirements:  Coombs control cells
A. Make a pooled ‘O’ Rho (D) positive cellsfrom at least three different ‘O’ positive blood samples. B. Wash these cells three times in normal saline (these cells should be completely free from serum with no free antibodies). Make 5 % salinesuspension of these cells

Procedure:
1.

Label three test tubes as ‘T” (test serum) PC (Positive control) and NC (negative control). In the tube labelled as ‘T’, add two drops of Anti-D serum Inthe tube ‘PC’ add one drop of saline Add one drop of 5 % saline suspension of the pooled ‘O’ Rho (D) positive cells in each tube. Incubate all the three tubes for one hour at 37°C

2. 3. 4.

5.Procedure: (cont.)
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Wash the cells three times in normal saline to remove excess serum with no free antibodies, (in the case of inadequate washings of the red cells, negative results may beobtained). Add two drops of Coombs serum (anti human serum) to each tube. Keep for 5 minutes and then centrifuge at 1,500 RPM for one minute. Resuspend the cells and examine macroscopically as well asmicroscopically

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Test Interpretation:
Observations 1 Positive Control (A) (PC)
(B)

Conclusions Correctly performed test procedure. Coombs serum may not be proper. Repeat the test...