Specimen Integrity, Rejection Criteria, and Labeling for Capillary and Special Collections

Why Specimen Integrity Matters

A laboratory result is only as reliable as the specimen behind it. For capillary and special collections — fingerstick microsamples, heelstick blood spots, glucose reagent strips, and point-of-care samples — the margin for error is especially small because sample volumes are already minimal. A rejected specimen means a delayed result, a repeat collection (patient discomfort), and potential harm if a critical value is missed. Your responsibility as a phlebotomy technician does not end when you place a tube in the rack; it ends when a properly labeled, intact, acceptable specimen is documented and delivered.

Labeling Requirements for Capillary and Special Collections

Every specimen must be labeled at the time of collection — not before, not later. The label must be applied directly to the primary container (the microtainer, filter paper card, or collection device), never only to the outer bag or transport envelope.

Standard required label elements include:

• Patient full name (first and last, spelled correctly to match the requisition or wristband)
• Patient date of birth (or a second unique identifier such as a medical record number)
• Date of collection
• Time of collection (critical for timed specimens such as glucose tolerance or therapeutic drug monitoring draws)
• Collector identification (your name, initials, or employee ID)
• Specimen source or test ordered (when required by facility policy)

For newborn screening filter paper cards, additional required fields typically include the infant's date and time of birth, gestational age, feeding status, and whether transfusions have occurred — because these variables affect result interpretation. Follow your facility's card instructions exactly; incomplete demographic sections are a common and serious rejection cause.

A label with even one missing element is an unacceptable specimen in most laboratories and accrediting body standards.

Common Rejection Criteria

Knowing why specimens are rejected allows you to prevent problems before they start and to respond correctly when they occur.

Hemolysis — Red or pink discoloration of plasma in a microtainer indicates ruptured red blood cells. Causes include excessive squeezing of the puncture site, too-vigorous mixing, or temperature extremes. Hemolysis artificially elevates potassium, LDH, and other analytes, making results unreliable.

Underfilling — Microtainers and other small tubes contain a measured amount of additive. If the specimen volume is below the minimum fill line, the additive-to-blood ratio is wrong. An underfilled EDTA tube, for example, will have excess anticoagulant relative to blood, which can shrink red cells and alter the complete blood count.

Clotted EDTA specimen — EDTA tubes must be mixed by gentle inversion immediately after collection to prevent clotting. A clotted EDTA specimen cannot be used for a CBC; the clot has already consumed platelets and altered cell morphology.

Unlabeled or mislabeled specimen — No label, an illegible label, or a label with incorrect patient information makes the specimen unacceptable. It cannot be relabeled after leaving the collector's sight unless your facility has a specific, documented exception protocol.

Wrong tube type — Collecting a specimen in a tube with the incorrect additive (or no additive when one is required) invalidates the test. For example, collecting a glucose specimen in a plain red-top rather than a gray-top (sodium fluoride) tube allows continued glycolysis and falsely lowers the glucose result.

Expired reagent strip or collection device — Expired materials may give inaccurate readings. Check expiration dates before every use. An expired strip is a rejected collection even if the technique was perfect.

Corrective Action and Documentation

When you identify a rejected specimen, act promptly and document completely. The corrective action log entry should include:

1. Patient identifier (name and date of birth or MRN)

2. Date and time of original collection

3. Nature of the problem (specific rejection reason)

4. Action taken (recollect, notify ordering provider, notify charge nurse, etc.)

5. Your initials or name

Documentation must be factual, objective, and free of personal opinion. Write what happened and what was done — not speculation about why. This record protects the patient, the laboratory, and you.

If recollection is needed, explain the reason to the patient calmly and professionally. Never attempt to relabel or salvage a specimen in a way that could misrepresent its identity or integrity.

Safety Considerations

• Never squeeze a capillary puncture site aggressively to increase flow; this introduces tissue fluid and causes hemolysis.
• Label at the bedside or collection site immediately — walking away with an unlabeled tube is a safety violation.
• Dispose of all lancets and capillary tubes in an approved sharps container immediately after use.
• Use standard precautions throughout; microtainer caps can spray if opened carelessly.
• When in doubt about specimen acceptability, consult the laboratory or your supervisor before releasing or discarding. Scope of practice means escalating decisions that are beyond your authority.