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Look-back, interfaces and bedside safeguards

15 min

Skills you'll build4 skills
  • Trace implicated components after a transfusion-transmitted infection report
  • Stop release when an interface converts a blank or invalid screen to negative
  • State the bedside identity check and administration rules for a component
  • Decide crossmatch or type and screen for a surgery from the blood order schedule

At the bench: Perform and document the laboratory workup of a transfusion reaction

Try first

Try first

A blood center reports that a donor's newest donation is repeatedly reactive for HIV. The same donor gave blood 5 months ago, and your transfusion service still holds frozen plasma from that earlier donation. What happens to that plasma?

Keep going to see the reasoning.

Keep going to see the reasoning.

Right. Keep going to follow the reasoning.

Keep going to see the reasoning.

Get the idea

Use the explanation to check your first decision.

Look-back

When a donation tests repeatedly reactive for HBV, HCV, HIV or HTLV, every earlier donation from that donor becomes suspect. The collecting facility notifies each hospital that received earlier components.1 The transfusion service then:

  1. Quarantines any earlier component still in date, pending supplemental testing.
  2. Finds the recipients of the earlier components that were transfused.
  3. Follows its procedure for notifying the recipient's physician if the infection is confirmed.1

When a recipient develops an infection that might have come from a transfusion, the transfusion service notifies the collecting facility promptly. Proof that a donor transmitted it is not needed first.2

LIS interfaces

An interface transfers analyzer results into the laboratory information system (LIS). One that maps a blank or invalid antibody screen to "negative" creates a result the analyzer never produced. That false negative can pass the electronic crossmatch check and release units without an antibody investigation.1,3 Only an explicit, valid final result code completes a screen. A blank, invalid or unknown code shows as unresolved and keeps its analyzer flag. Under the laboratory's rules, an unresolved screen is ineligible for electronic crossmatch.3

Bedside identification and administration

Identity is checked at collection, at testing, at issue and at the bedside. Immediately before infusion, at the patient, the final check matches the patient's identifiers, the unit label and the compatibility record. Bedside clerical error remains the leading preventable cause of fatal ABO-incompatible transfusion.1,4

Administration ruleReason
Only 0.9% sodium chloride runs with the componentOther solutions lack compatibility data
No dextrose solutions in the lineDextrose hemolyzes red cells
No calcium solutions, such as lactated Ringer'sCalcium reverses the citrate and clots the line
A standard 150- to 260-micron filterIt removes clots and aggregates
Finish within 4 hours of entering the containerLonger at room temperature increases the risk of bacterial growth

Ordering for surgery

Most operations need no transfusion. A maximum surgical blood order schedule (MSBOS), built from the facility's own transfusion data, lists which procedures get crossmatched units and which get a type and screen only. With a type-and-screen policy, it keeps the crossmatch-to-transfusion ratio near 2:1 to 3:1. It also saves inventory and testing time for patients with antibodies.1

Follow the bench demonstration

Sources for this step
References
  1. Bloch EM, Campbell-Lee S, McKenna DH Jr, Montemayor-Garcia C, Schwartz J, Shaz B, Storry J, eds. Technical Manual. 22nd ed. AABB; 2026.
  2. Centers for Disease Control and Prevention. National Healthcare Safety Network. Biovigilance Component Hemovigilance Module Protocol. Version 3.0. January 2026. Accessed September 27, 2026.
  3. US Food and Drug Administration. Blood Establishment Computer System Validation in the User's Facility: Guidance for Industry. April 2013. Accessed September 27, 2026.
  4. Association for the Advancement of Blood & Biotherapies, American Red Cross, America's Blood Centers, Armed Services Blood Program. Circular of Information for the Use of Human Blood and Blood Components. June 2024. Accessed September 27, 2026.

Watch one

Read each decision and its explanation.

At 02:10 the operating room asks for 2 red-cell units for Farid Glass, 61 (MRN 6620194). The LIS shows his antibody screen as Negative and marks him eligible for electronic crossmatch. The interface from the antibody-screen analyzer was replaced this week.

What do you do before issuing units?

  1. Open the analyzer's record for his specimen. It shows an invalid flag and a blank interpretation field.

    The analyzer record shows the original result. The LIS shows the result after interface mapping.

  2. Treat the screen as unresolved.

    A blank field is not an interpretation. Only an explicit, valid final result code completes a screen.

  3. Remove his electronic crossmatch eligibility, and issue no units on this screen.

    An unresolved screen cannot show that he lacks clinically significant antibodies.

  4. Repeat the antibody screen on his specimen.

    A valid result determines the next step: an electronic crossmatch, or an antibody investigation.

  5. Report the fault to the supervisor as a nonconformance.

    The same mapping handles every screen, so other results sent since the change may have the same error.

The screen is unresolved. No units go by electronic crossmatch until a valid screen result exists, and the interface fault is reported so that earlier results through the same mapping can be checked.

Practice this skill

Your turn

Problem 1 of 3 · Hints available

An analyzer sends an invalid antibody-screen flag with a blank interpretation. How does the receiving system record the result?

Correct. Only an explicit valid final result code completes the screen. The receiving system records this screen as unresolved and keeps the analyzer flag. Under the laboratory's rules, electronic crossmatch requires a valid completed screen.

Incorrect. A blank field contains no interpretation. Mapping it to negative is the defect found during validation, because it lets an unfinished test pass as a completed negative screen.

Incorrect. Acceptable quality control shows the analyzer performed as expected. It cannot supply the missing interpretation for this specimen, so the screen stays unresolved.

Hint
  1. Consider what a blank interpretation field means for this specimen.
  2. Quality control describes the analyzer's run. Ask whether it can supply one specimen's missing result.

Review An interface that turns an invalid screen into a negative result

Problem 2 of 3 · Hints available

A red-cell unit has been issued and carried to the ward. Immediately before infusion, what does the final identification check compare?

Incorrect. The label and the record can agree with each other and the unit can still be hung on the wrong patient. Only a check made at the patient confirms who receives it.

Correct. Clerical error at the bedside remains the leading preventable cause of fatal ABO-incompatible transfusion, so the patient's identifiers, the unit label and the compatibility record are matched together at the patient immediately before infusion.

Incorrect. Two patients can share a name and a blood group. The check uses two independent patient identifiers and the donation identification number that links the unit to the compatibility record.

Hint
  1. Ask where the patient is when the final check happens.
  2. Two patients can share a name and a blood group. Think about which identifiers link one patient to one unit.

Review Administration safeguards

Problem 3 of 3 · On your own

A patient is scheduled for a laparoscopic cholecystectomy. The facility's MSBOS lists type and screen only for this procedure. His antibody screen is negative, and he has no antibody history. What does the transfusion service prepare before surgery?

The schedule lists this procedure as type and screen only, because it seldom needs blood. Reserved units go unused and raise the crossmatch-to-transfusion ratio.

Crossmatched units for a type-and-screen-only procedure

A maximum surgical blood order schedule lists, from the facility's own transfusion data, which procedures need crossmatched units and which need only a type and screen. Crossmatching for a type-and-screen procedure reserves units that are seldom used, pushes the crossmatch-to-transfusion ratio above its target of 2:1 to 3:1, and takes inventory and testing time from patients with antibodies.

Without a type and screen, the first unit would wait for ABO, D and antibody testing. The schedule requires that testing before the procedure.

The schedule is built from the facility's own data for this procedure. Reserving four units ties up inventory for a transfusion that rarely happens.

The negative screen and absence of antibody history mean units can be issued quickly by the crossmatch the policy allows. Inventory remains available for patients who need it.

Review Surgical blood ordering

Use it

Read the case evidence, then make each decision. The step is complete without it.

  • Northfield Blood Center calls your transfusion service.
  • A regular donor's latest donation is repeatedly reactive for anti-HCV. Supplemental testing is pending.
  • The same donor gave blood 4 months ago. Your hospital received that donation's red cells and frozen plasma.
  • The red cells were transfused 3 months ago to Walter Piper, 74 (MRN 3307821), a retired ferry captain.
  • The plasma is still in your freezer and in date.
Decision 1 of 3

What do you do with the plasma?

The earlier donation is now suspect. Quarantine prevents the plasma from being issued while testing is completed.

The earlier test could have fallen in the window before infection was detectable. The new result is the reason every earlier donation is now suspect.

Quarantine applies to the donor's earlier in-date components too. Leaving the plasma available could send a possibly infectious unit to a patient.

Quarantined only the current positive donation

A repeatedly reactive donation for HBV, HCV, HIV, or HTLV makes earlier donations from that donor within the lookback period suspect. In-date components from those donations are quarantined pending supplemental testing while the collecting facility and transfusion service trace where they went. Stopping at the current donation leaves possibly infectious components available for issue.

Review Look-back, quarantine, and reporting

Decision 2 of 3

What about the red cells Mr. Piper received?

The look-back traces transfused units. If the infection is confirmed, his physician must be notified.

Supplemental testing on the donor is still pending, and he has not been tested. Notification goes through his physician under the procedure, once the result is confirmed.

The transfusion record links the unit to him. The procedure sets who notifies his physician and when.

Review Look-back, quarantine, and reporting

Decision 3 of 3

The same week, a patient transfused 2 months ago develops acute hepatitis B. What does the transfusion service do?

Proof of transmission is not needed before a report. Waiting leaves the donors' other components available for transfusion.

The collecting facility can trace the donors and quarantine their other components only after it receives the report. The investigation continues after the report.

A chart note does not reach anyone who can trace the donors. The collecting facility needs the report to protect other recipients.

Review Look-back, quarantine, and reporting

The earlier donation still had in-date plasma in the freezer. A nonreactive test at collection can fall in an infection's window period, so today's reactive result makes the older donation suspect. Quarantine prevents the plasma from being issued, and the transfusion record identifies who received the red cells.

For reference

Sources checked