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Hematology

Indirect Coombs test before an operation or blood transfusion

In a blood transfusion, someone else's blood enters the bloodstream, and according to the RIVM the body can make antibodies against blood groups it does not have itself when it comes into contact with the blood of someone with a different blood group. According to MedlinePlus, an indirect Coombs test looks for such antibodies against red blood cells in the blood.

According to the NVKC, when irregular antibodies are found in a patient's blood, this has consequences for the blood transfusion. Only a blood test shows whether someone has such antibodies.

According to MedlinePlus, a normal result is called a negative result, and Diagnostiek voor U states ‘Geen eenheid van toepassing’, no unit applicable, for the screen.

Doctor's Assessment Included

The indirect Coombs test looks for antibodies against red blood cells that are free in the blood. According to the NVKC, it is another name for the irregular antibody test, and irregular antibodies are normally not present in the blood.

  • The indirect Coombs test result is a conclusion without a unit: Diagnostiek voor U uses ‘Negatief’ (negative) as its target value, Unilabs records ‘niet aantoonbaar’ (not detectable).
  • According to the NVKC, the indirect Coombs test is requested before a blood transfusion, before an operation that may need a transfusion, and in week 12 of pregnancy.
  • According to the NVKC, when irregular antibodies are found, specially matched blood is sometimes needed for a transfusion.

Reference Ranges

Expected result Negative

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

Check your own value

Coombs Test (Indirect): what this test measures

An indirect Coombs test before a transfusion determines whether irregular antibodies are in the blood, defence substances against red blood cells of another blood group. Unilabs performs the determination together with the blood group and the rhesus factor, under the name ‘Bloedgroep / rhesus / antistofscreening’ (blood group, rhesus, antibody screen). The NVKC calls the same determination the irregular antibody test.

Coombs Test (Indirect): why this value matters

An indirect Coombs test before an operation matters because, according to the NVKC, when irregular antibodies are found, specially matched blood sometimes has to be selected for the patient.

Coombs Test (Indirect): how the blood test works

Referral
No GP referral needed. After the order we arrange the referral through ZorgDomein, within one business day; orders after 17:00 or at the weekend start on the next business day. ZorgDomein emails a barcode, and that barcode is what the draw site needs.
The draw
A blood draw from a vein in the arm, at a partner laboratory's draw site. No home kit, no finger prick.
Where
650+ draw sites run by independent laboratories across the Netherlands. Draw sites

Coombs Test (Indirect): when is testing worthwhile?

According to the NVKC, the indirect Coombs test is requested before an operation in which someone may need a blood transfusion. According to MedlinePlus, no special preparation is necessary.

Coombs Test (Indirect): symptoms of a high or low value

Low Levels

According to MedlinePlus, a negative indirect Coombs test is the normal result, and according to MedlinePlus it means there was no clumping of cells in the test.

High Levels

According to MedlinePlus, a positive indirect Coombs test before a transfusion may suggest an incompatible blood match, when the test is used in a blood bank.

Coombs Test (Indirect): causes of a low or high value

What raises the value

  • Blood transfusion

    Irregular antibodies can be formed when ‘foreign’ blood enters the circulation, and that can only happen through a blood transfusion or during a pregnancy.

  • Pregnancy

    During a pregnancy, a little blood from the unborn child can enter the mother's bloodstream, against which she can form irregular antibodies.

Coombs Test (Indirect): lifestyle and this value

Take a positive indirect Coombs test before an operation to the doctor planning the operation or to your GP.

Coombs Test (Indirect): frequently asked questions

Why is there an antibody test before an operation?

According to the NVKC, irregular antibodies are tested for before an operation with a possible blood transfusion, because antibodies that are found have consequences for that transfusion.

Coombs Test (Indirect): sources

  1. NVKC, Alles over testen: Irregulaire antistoffen, allesovertesten.nl, geraadpleegd 2026-10-17 (retrieved 2026) allesovertesten.nl

Tests with related values

These panels measure values from the same category as this marker.

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Medical policy
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Coombs Test (Indirect)

€33,-