Software Processes–Direct Antiglobulin Test

Tests and Reagents:

There are many variations for this most important test.  In the very least, this consists of:

  1. Screening polyspecific AHG for detecting IgG and/or complement
  2. If positive, reflex monospecific tests to distinguish IgG from C3 reactivity

There are many kinds of reagents:

  1. Immunoglobulin:  whole molecule IgG, monospecific gamma heavy chain, monospecific alpha heavy chain, monospecific mu heavy chain
  2. Complement:  C3d, C3c, C3b, C5, etc

Regretfully, some of the monospecific are not really monospecific (e.g. whole molecule IgG detects both heavy and light chains and thus may detect IgG and give weaker results for IgM or even IgA.)

For the software builder, there are at least the monospecific and polyspecific tests but the manufacturers may not use the same specificities in their reagents.  Thus, when I was at HMC Doha, we had many different DAT tests, each of which required a separate software process for each type of interfaced, automated equipment as well as the manual processes for each kind of reagent.


Fortunately, Medinfo is rules-based so we could use existing rules to control the allocation of blood components and production based on the DAT results.

If the DAT test was positive, this would further trigger acid-elution testing and possibly an antibody identification.  Based on the antibody results, this would trigger rules about antigen-matching and preclude use of the electronic crossmatch for that patient.  For a donor, the detection of an antibody could trigger a contraindication to his eligibility and the use of his blood for patients.

Interface of Medinfo DAT to Hospital Information System:

I have seen some non-blood-bank laboratory systems built where specific versions of a test were restricted to a particular site, and the order for that test was specific to that site.  So, they had to reorder the test at another site if the original site was down.

I personally think this is suboptimal.  First, before building the blood bank system, we unified our processes as much as possible.  This allowed us to use the same workflows at all sites, the only difference being some equipment and reagents.

Even so, I built Medinfo processes to allow all testing at all sites.  This is very useful in case of an emergency so we could shift work around easily and not have to reorder.  In other words we could use ANY DAT test for any DAT order.  Also, since we used both Medinfo donor and patient modules, we could use the same algorithms for both

For interfaces with Medinfo, the hospital information system HIS was only allowed to send an order for the TYPE of test, not the actual test methodology.  When the order was received in Medinfo, the blood bank technical staff selected which DAT algorithm to use.  This meant mapping all possible combinations of results for all tests back in the HIS.

Examples of some of the DAT methodologies follow.

To Be Continued:


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