Coomb test in blood bank (anti-globulin test) principle, procedure

Coomb test or anti-globulin test is an important test in blood bank. Coomb’s test has two types dirct coomb test and indirect coomb test.

This test is used assess the sensitized red blood cell. RBC sensitized by the IgG antibodies or by the complements.

How many types of coomb test in blood bank?

There are two types Coombs test in blood bank.

  1. Direct Coomb test
  2. Indirect Coomb Test

what is the Quality control (Check cell) in coomb test?

Coomb serum checked by the known sensitized red blood cells. These known sensitized red cell can be prepared or commercially availble.

What are the source of errors in coomb test in blood bank

Coomb test two kinds of source of errors.

  1. False Negative Test
  2. False Positive Test

False Negative Test in coomb test

  1. Test tube pipett can be direty.
  2. Red call in adequaetly washed.
  3. Protein on figertipes can neutralized the anti-human globulin. It result in false negative.
  4. Incubation time too short or too long.
  5. Delay in reading will result in false negative. Delay in reading allowing the antibodies to be eluted off the cell.
  6. Test cell were storeged improperly result in loosing thier activity.
  7. Change in the optimal ratio of antibody to antigen.
  8. Plasma is used instead of serum.
  9. Under cetrifugation

False Positive Test in coomb test

Following are the possible causes of false positive coomb test.

  1. Saline contamination with heavy metal ions, and colloidal silica can cause agglutination.
  2. Bacterial contamination of test.
  3. Refrigerated, clotted sample cause non specific binding C4, which react with anti-compliment of anti-globuline serum.
  4. Over Centrifugation can result in False positive test.

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