16.1 Blood Sample Quality Assurance

16.1 Blood Sample Quality Assurance

Quick Answer: Identify every blood-bank specimen with two independent identifiers that match the request. Reject unlabeled and mislabeled tubes — never relabel from memory. If the patient was transfused or pregnant in the last 3 months, or the history is uncertain, AABB requires a sample drawn within 3 days of the scheduled transfusion (day of draw = day 0). EDTA plasma is the routine specimen; fresh serum is what you need when complement must still work. Preanalytical errors, especially wrong blood in tube (WBIT), are the most common cause of ABO mistransfusion. Retain recipient samples at 1–6 °C for at least 7 days after transfusion. Wash cord cells. Use the maternal sample for the infant antibody screen.

The June 9, 2026 BB outline parks blood-sample quality assurance at IV.D. Chapters 13–15 already taught what you do with a good specimen. This section is how you refuse a bad one. Most ABO mistransfusions are not mysterious reagent failures. They start with the wrong wrist, the wrong sticker, a line draw soaked in saline, or a 5-day-old tube on a just-transfused patient.

Two identifiers, and the tubes you never “save”

AABB, CLIA, and The Joint Commission all require two independent identifiers on the sample and on the request. Typical pairs are full legal name plus medical-record number, or name plus a unique blood-bank band number. Date of birth is a common second identifier on outpatient tubes; a room number, “blood bank,” or “OR hold” is not an identifier. The phlebotomist identifies the patient, labels the tube at the bedside, and the blood bank compares the tube to the order before any reagent is opened.

Unlabeled tubes are discarded and redrawn. You do not write the name on after the fact because the nurse “knows whose it is.” A mislabeled tube — name and MRN that do not match each other, or do not match the order — is the same reject. A tube that arrives with one identifier only is incomplete. The dangerous cousin is wrong blood in tube (WBIT): the label is internally consistent and matches the order, but the blood inside belongs to someone else. WBIT looks legal. The only bench clue is a type that disagrees with history, a sudden extra reverse agglutinin, or a crossmatch that does not fit. That is why historical ABO comparison is not optional decoration. It is the last check against a perfectly labeled wrong sample.

Hemolyzed, lipemic, and IV-contaminated samples

In-vitro hemolysis comes from a traumatic stick, a tiny needle, forcing blood through a line, vigorous shaking, delayed processing, or a freeze-thaw. Free hemoglobin can mask hemolysis as a positive endpoint in tube methods and will fail many solid-phase assays. Most laboratories reject frankly hemolyzed type-and-screen tubes when the hemolysis is an artifact. In-vivo hemolysis is different: a possible hemolytic transfusion reaction, AIHA, or mechanical shear. Those samples must be tested, documented as hemolyzed, and interpreted with the clinical picture. Rejecting the only post-transfusion specimen because it is pink is how you miss an HTR.

Lipemia (TPN, lipid emulsion, a non-fasting draw) clouds automated optical reads and some gel/solid-phase wells. Redraw or, if the SOP allows, clear the plasma. Do not “read around” a milky well and call the screen negative.

IV contamination is a preanalytical ABO and antibody-screen killer. Dilution with saline or crystalloid weakens reverse-type isoagglutinins and unexpected antibodies — a group O can look like a missing reverse, and a real anti-Jka can drop below detectability. Dextrose can cause false agglutination or in-vitro hemolysis. Lipid emulsions add lipemia. Heparin-lock fluid can delay clotting in a serum tube. Prefer a peripheral venipuncture below, or in the other arm from, a running IV. If a line draw is unavoidable: stop the infusion, flush, discard a waste volume (typically twice the line dead space, often 5–10 mL in adults), then fill the blood-bank tube, and document the line. Never draw above a running infusion.

Specimen age: the 3-day rule

If the patient was transfused or pregnant within the preceding 3 months, or the history is uncertain, AABB requires the sample used for pretransfusion testing to be obtained within 3 days of the scheduled transfusion. Day 0 is the day of collection. A Monday draw is valid through the end of Thursday, not “72 hours to the minute” unless your SOP is written that way. The clock exists because a newly stimulated alloantibody — classically Kidd — can appear days after transfusion or delivery. Testing a week-old leftover tube on a just-transfused ICU patient is how you miss that antibody.

If there has been no transfusion and no pregnancy in 3 months and the history is documented, a facility may validate a longer window for outpatient type-and-screen (often up to 14 days). That extension is policy plus a reliable history, not a free pass. When in doubt, redraw. The exam stem that says “transfused last week” or “delivered 6 weeks ago” wants the 3-day sample.

Serum versus EDTA plasma

EDTA (lavender or pink) is the everyday immunohematology tube. It chelates calcium, so complement cannot assemble in vitro. That is useful: you avoid in-vitro complement coating that is not happening in the patient, and the cells stay DAT-stable for typing. It is also a limitation: EDTA plasma will not show complement-dependent hemolysis (some Kidd, ABO, or PCH-style in-vitro hemolysins). When the question is “does this antibody hemolyze?”, you need fresh clotted serum (red-top, no anticoagulant, complement intact). Do not use a serum-separator gel tube as a default blood-bank specimen — gel can trap cells and interfere. Heparin is not a blood-bank tube.

Plasma can throw fibrin strands that look like agglutination if the draw was incomplete or the tube was underfilled. Serum avoids fibrin but clots slowly and is a poor DAT tube if you needed cells from the same specimen. Many laboratories collect a pink-top EDTA for type, screen, DAT, and crossmatch, and add a red-top only when the workup needs complement.

Retention, neonates, and maternal samples

AABB requires recipient samples (and a segment from issued red-cell-containing units) to be stored at 1–6 °C for at least 7 days after transfusion. That retained tube is the investigation specimen for a delayed reaction, a wrong-unit trace, or a requested add-on DAT. Do not discard Friday’s crossmatch racks on Saturday morning.

Neonates need extra sample discipline, not extra volume. Cord blood is coated with Wharton jelly, which causes false extra forward agglutination — wash thoroughly before typing (Chapter 13). A cord tube still needs two identifiers that distinguish infant from mother. Do not type the mother off a cord label. The maternal specimen is the preferred sample for the infant antibody screen in the first months of life, because circulating antibody is maternal IgG. The infant contributes a washed forward type, a DAT, and, when the mother is D-neg, a weak D. Heel-stick or venous microtainers are acceptable if labeled at the bedside; do not pool unlabeled leftover drops “to make enough.” Keep the maternal sample available for crossmatch if the infant needs blood.

Worked scenario. A group A patient transfused 4 days ago has a type-and-screen drawn from the same arm as a running saline IV. The reverse type is weak, the antibody screen is negative, and the historical file is A-positive with anti-E. Treat the specimen as invalid (diluted and too old if it was a leftover from last week) — redraw below the IV or from the other arm, inside the 3-day window, and honor the historical anti-E even if today’s screen is blank.

Exam traps

• Relabeling an unlabeled tube because the sender “confirmed” the name on the phone.
• Using a 5-day-old sample on a patient transfused last week.
• Treating hemolyzed post-transfusion plasma as automatically rejected rather than as a possible HTR specimen.
• Drawing above a running IV and trusting the reverse type.
• Using EDTA plasma to demonstrate in-vitro hemolysis.
• Reverse-typing a neonate, or issuing blood on an unwashed cord forward type.
• Throwing out retained samples before 7 days after transfusion.