Processes and Software Building—Part 19

In the previous post I outlined how Medinfo handled antibody screening and identification.  This post reviews how antigen matching is used based on these results.

There are two modes, regular and emergency.  If the patient has not had at least two ABO/D determinations and/or does not have a recent antibody screen, then emergency mode must be selected with its own rules.  Otherwise, the regular mode applies.

Regular Mode:

In general, if there is a clinically significant antibody, an RBC unit which has not been matched for the corresponding antigen or has the corresponding antigen cannot be routinely selected.  However there is a hierarchy here also:

1. Absolutely prohibited release—no one can override the logic (e.g. giving group O to a patient with anti-H)—not even the transfusion medicine physician can override this
2. Restricted release—only certain staff can release the incompatible or untested unit (e.g. giving C-positive unit to someone with anti-C)
3. Least-incompatible for WAIHA:  requires transfusion medicine physician approval
4. Informational release:  authorized staff may release antigen-incompatible or untested unit but a pop-up menu appears and asks them to accept (e.g. Lewis untested unit in a patient with anti-Lea).
5. Antigen-specificity matched—the usual mode for patients with antibodies

Examples of Regular Mode rules follow (these are not the complete lists but just provided to show the complexity of the process).

Emergency Mode:

This is much more restricted for selection of ABO/D and other antigen typings.  An example follows:

A similar hierarchy exits for platelet and plasma allocation and will be considered in a future post.

To Be Continued:

18/7/20

Processes and Software Building—Part 17

The direct antiglobulin test DAT may be the first or last place that a delayed hemolytic transfusion reaction can be detected.  In my practice, I always performed it the first time I encountered a patient with a positive DAT.  If the subsequent DAT testing is of the same strength and there is no change in the clinical status of the patient, then I might empirically repeat the elution after 14 days, i.e. just when new antibody emergence may be detected.

In summary, my criteria for elution after a positive DAT are:

1. First patient encounter with a positive DAT
2. At least 14 days since the previous elution
3. DAT strength has increased since the previous exam (at least 1+ increase in strength in either IgG or C3)
4. Patient shows evidence of hemolysis
5. Suspected cases of drug-related hemolysis
6. Transfusion Medicine physician specifically orders it otherwise

In the software processes, the following parameters were recorded:

1. Technique of elution (acid glycine, dichloromethane, digitonin, ether, etc.)
2. Number of washes (too many may remove the antibody from the RBCs)
3. Last wash result (must be negative to accept conclusion)
4. Manufacturer of the elution kit (if any)
5. Elution result based on panel testing

Note:

1. All indeterminate or positive eluates would trigger an antibody identification.
2. All results would be reviewed by me or the covering Transfusion Medicine physician.  A comment would be entered into the results that could be viewed by the clinician either directly from Medinfo or through the hospital information system.

If the DAT was only positive for complement, it was up to the Transfusion Medicine Consultant to decide whether to proceed with elution.  Personally, I would usually proceed because the eluate is more concentrated and may occasionally detect an antibody that was not noted in the patient’s plasma.

The attached Medinfo workflow shows the process designed by me for use at HMC Doha.

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.)

Read More »

The electronic/computer crossmatch is vital to the hospital blood bank’s operation.  It allows us to reduce unnecessary work and redeploy a very limited, precious workforce.  As demonstrated in the previous post, it has many rules for current and previous testing and historical transfusion records.

This is NOT a one-time validation:  it must be repeated to check for regression errors when updating the software version, regardless if there are any changes to its logic.  It required many Super-Users to perform:

1. A test environment distinct from the live was used.
2. Patients had to be created and specific test results entered to match the algorithm below.
3. Donors had to be created and components made (including testing, production, release, inter-depot transfer)
4. Hospital blood bank had to receive the created units and enter them into active stock (and repeat the ABO/D testing to do this)

This is a sample validation plan created by me and used at HMC Doha for the Medinfo Hematos IIG software:

1. Special Electronic Crossmatch Testing
   1. Make 100 patients:
   2. 60 patients matching electronic crossmatching criteria:
      1. 2 ABO/D determinations, one current within 72 hours
      2. Second determination from history or second current sample
      3. No ABO/D typing discrepancies
      4. Negative antibody screen
      5. No history of antibodies
   3. 40 patients with contraindications to electronic crossmatch:
      1. 10 with history of antibody
      2. 10 with current antibody
      3. 10 without 2 ABO/D determinations
      4. 10 with emergency release
   4. Try to release RBC unit without further testing in each case.

Super Users had to capture screen shots of the transactions and send them to me as Division Head, Transfusion Medicine/LIS for review and acceptance.

Criteria for Acceptability:

1. All tested processes must complete without error, including recognition of ABO/D discrepancies as such.
2. System only allows computer release (electronic crossmatch) in those cases meeting computer-crossmatch criteria as shown in the following interim policy.

INTERIM POLICY:  ELECTRONIC (COMPUTER) CROSSMATCH

Revised Date:  1/2/18

Principle:

In selected patient categories, no classical crossmatch may be required for release of RBC components.  The criteria are specified here as applicable in our Medinfo Hematos IIG computer system HIIG.

Policy:

1. An electronic crossmatch without antiglobulin or immediate-spin phase testing may be used for the following patient categories:
   1. The current ABO/D type matches the historical ABO/D type.
   2. The ABO/D type (forward and reverse) is clearly defined without any discrepancies.
   3. Two determination of the ABO/D group must be made:
      1. One from a current specimen (within the past 72 hours)
      2. The second by one of the following methods:
         1. Testing a second current specimen
         2. Comparison with previous records of ABO/D typing
         3. Retesting the same specimen
   4. The current antibody screen is negative
   5. There is no history of RBC antibodies or a non-negative antibody screen.
2. General computer system safeguards:
   1. The system contains the donor unit number, component name, confirmed ABO/D typing, two unique recipient identifiers, recipient ABO/D, antibody screen typing, and interpretation of compatibility
   2. A method exists to verify correct entry of data before release of blood or blood components.
   3. The system contains logic to alert the user to discrepancies between donor ABO/D group on the unit label and those determined by blood confirmatory tests and to ABO incompatibility between the recipient and donor unit.
3. HIIG will enforce the above rules.

References:

1. HIIG Workflow 1004, Patient Testing, 2013
2. Section 5.16, Standards for Blood Banks and Transfusion Services, Current Edition, AABB, Bethesda, MD, USA
3. FDA Guidance for Industry:  Computer Crossmatch (Computer Analysis of the Compatibility between the Donor’s Cell Type and the Recipient’s Serum or Plasma Type), April, 2011

As much as 90% of the RBC component allocation can be performed without an actual crossmatch test—AHG or immediate-spin provided that certain criteria are met.

Enforcing these rules, however, can be cumbersome unless one has blood bank software that verifies that each rule is met.  In the Medinfo patient module, the transfusion history database is checked automatically.  If the rules are met, then Medinfo allows the selection (allocation) of RBC units without performing a crossmatch test.  Otherwise, it will check to see if the AHG crossmatch has been done within the past 3 days.  If not, it will prompt for new crossmatch testing with a new specimen.  If the situation is urgent, one can go to Emergency Mode and release components without the crossmatch.

The following is the latest document I prepared on this process before leaving HMC.  Please note that there was an extensive validation before this was activated for patient use.

INTERIM POLICY:  ELECTRONIC (COMPUTER) CROSSMATCH

Revised Date:  1/2/18

Principle:

In selected patient categories, no classical crossmatch may be required for release of RBC components.  The criteria are specified here as applicable in our Medinfo Hematos IIG computer system HIIG.

Policy:

1. An electronic crossmatch without antiglobulin or immediate-spin phase testing may be used for the following patient categories:
   1. The current ABO/D type matches the historical ABO/D type.
   2. The ABO/D type (forward and reverse) is clearly defined without any discrepancies.
   3. Two determination of the ABO/D group must be made:
      1. One from a current specimen (within the past 72 hours)
      2. The second by one of the following methods:
         1. Testing a second current specimen
         2. Comparison with previous records of ABO/D typing
         3. Retesting the same specimen
   4. The current antibody screen is negative
   5. There is no history of RBC antibodies or a non-negative antibody screen.
2. General computer system safeguards:
   1. The system contains the donor unit number, component name, confirmed ABO/D typing, two unique recipient identifiers, recipient ABO/D, antibody screen typing, and interpretation of compatibility
   2. A method exists to verify correct entry of data before release of blood or blood components.
   3. The system contains logic to alert the user to discrepancies between donor ABO/D group on the unit label and those determined by blood confirmatory tests and to ABO incompatibility between the recipient and donor unit.
3. HIIG will enforce the above rules.

References:

1. HIIG Workflow 1004, Patient Testing, 2013
2. Section 5.16, Standards for Blood Banks and Transfusion Services, Current Edition, AABB, Bethesda, MD, USA
3. FDA Guidance for Industry:  Computer Crossmatch (Computer Analysis of the Compatibility between the Donor’s Cell Type and the Recipient’s Serum or Plasma Type), April, 2011