Why lab specimens get rejected, and how to prevent it at the draw
Why rejections matter
A rejected specimen means a redraw. The patient is stuck again, results are delayed, and staff spend time recollecting and re-couriering. Reported rejection rates vary widely by setting and specimen type, roughly 0.1–3.5% across published studies.[1] Even a low rate adds up. At 150 draws per month, a 1% rejection rate is about 18 redraws a year.
The pre-analytical phase accounts for a majority of lab errors, classically cited as 60 to 70%.[2] That is the part of the process that lives at the chair, which is also where it can be prevented.
Top 8 reasons specimens get rejected
| Rejection reason | What typically causes it during collection or handling | How to prevent it |
|---|---|---|
| Hemolysis | Difficult stick, small-gauge needle, forceful aspiration, vigorous mixing, prolonged tourniquet, or alcohol not fully dry. | Use appropriate technique per guidance, release the tourniquet promptly, let alcohol dry, and invert gently (do not shake). |
| Insufficient volume (QNS) | Underfilled tube, wrong tube size for the panel, or not checking the minimum volume before drawing. | Confirm the required volume and tube before drawing, and fill to the line. |
| Clotting (anticoagulant tube) | Delayed or incomplete mixing after the draw. | Invert the correct number of times immediately after filling, per manufacturer guidance. |
| Wrong tube or additive | Grabbing the wrong top color or additive for the test. | Verify the tube type against the order before venipuncture. |
| Additive carryover (wrong order of draw) | Drawing tubes out of the CLSI sequence, so additive carries over from one tube to the next. | Follow the CLSI order of draw for every multi-tube collection.[3] |
| Labeling error or missing label | Labeling away from the patient, or an incomplete set of identifiers. | Label at the chair and verify two patient identifiers before the patient leaves.[4] |
| IV contamination or dilution | Drawing above an active IV, or from a line without a proper discard. | Prefer a free-flowing peripheral stick. If a line is used, follow your lab and facility protocol. |
| Improper temperature or delayed transport | Left at the wrong temperature, or held too long before the courier. | Know the storage requirement before the specimen leaves the room, and hand it off promptly. |
What causes hemolysis, and how to prevent it
Hemolysis is the rupture of red blood cells that releases their contents into the specimen, which can make it unsuitable for testing. Prevention steps, per lab or manufacturer guidance:
- Use appropriate technique and an appropriate needle size for the vein.
- Release the tourniquet promptly rather than leaving it on for a prolonged draw.
- Let the alcohol dry fully before the stick.
- Avoid forceful aspiration.
- Mix by gentle inversion, and do not shake the tube.
What does QNS mean, and how to prevent insufficient volume
QNS stands for quantity not sufficient: the specimen did not have enough volume for the test. The usual cause is an underfilled tube or the wrong tube for the panel. Confirm the required volume and tube before the draw, and fill to the line. Some tubes also depend on a correct blood-to-additive ratio, so an underfill can be a problem even when there seems to be enough sample. Check the lab's guidance for specific volumes rather than assuming a number.
How to prevent clotting in anticoagulant tubes
Clotting in an anticoagulant tube usually comes from delayed or incomplete mixing after the draw. Invert the tube promptly, the number of times specified by the tube manufacturer. Invert gently, do not shake.
Choosing the right tube and additive
Verify the tube against the order before drawing. When you are not sure which tube or how much volume a test needs, check the lab's directory rather than guessing. If you want tube type, volume, and order codes for a specific test pulled together in one place, a LabLookup search returns them for Quest, LabCorp, and BioReference. For a color-by-color reference, see the tube guide.
The order of draw
Additive carryover between tubes is a preventable cause of rejection, so multi-tube collections follow the CLSI sequence.[3] Rather than reproduce the full sequence here, see the printable order of draw chart.
Labeling and patient identification
Label at the chair, and verify two patient identifiers before the patient leaves.[4] Do not pre-label tubes or batch-label them away from the patient, since that is where mislabeling starts.
A printable checklist for before, during, and after the draw
- Confirm the test, tube type, and additive against the order.
- Confirm the required volume and tube size.
- Know the storage and transport requirement before you start.
- Let the alcohol dry, then stick. Release the tourniquet promptly.
- Fill each tube to the line. Draw multiple tubes in CLSI order.
- Invert each anticoagulant tube gently, per manufacturer count. Do not shake.
- Label at the chair and verify two patient identifiers.
- Hand the specimen off promptly at the right temperature.
- If anything looks off (short fill, clot, hemolysis), recollect rather than send.
Frequently asked questions
What is the most common reason for specimen rejection?
Most rejections are pre-analytical, meaning they happen during collection, handling, or transport rather than during testing. Hemolysis, insufficient volume (QNS), and clotting are among the most commonly reported causes. Reported rates vary by setting and specimen type.
What does QNS mean on a lab result?
QNS stands for quantity not sufficient. It means the specimen did not have enough volume for the test, usually because the tube was underfilled or the wrong tube was used. Confirming the required volume and tube before the draw, and filling to the line, prevents most QNS rejections.
Why does the order of draw matter?
Small amounts of additive can carry over from one tube to the next during a multi-tube collection. Drawing tubes out of sequence can let that carryover interfere with the next specimen, which can cause a rejection. Following the CLSI order of draw prevents it.
How do you prevent hemolysis during a blood draw?
Hemolysis is the rupture of red blood cells, which can make a specimen unusable. Prevention steps, per lab or manufacturer guidance, include using appropriate technique and needle size, releasing the tourniquet promptly, letting alcohol dry before the stick, and mixing gently by inversion rather than shaking.
Preventing rejections mostly comes down to having the right tube, volume, order, and handling information in front of you at the moment of the draw, which is exactly what a point-of-care reference is for. Try a LabLookup search or estimate the cost of avoidable redraws with the rejection cost calculator.
A logistics-only reference, clinically reviewed. This page covers specimen handling, not test interpretation, diagnosis, or clinical decisions. Requirements vary by lab and by tube manufacturer, so check your lab's test directory and your facility's procedures before clinical use.
- [SOURCE: 2023 specimen-rejection meta-analysis, roughly 2% pooled rejection rate; CAP Q-Probes, chemistry rejection medians roughly 0.2 to 0.35%.] To be verified during clinical review.
- [SOURCE: Plebani and Bonini, "Errors in laboratory medicine," Clinical Chemistry. The pre-analytical phase is classically cited as accounting for 60 to 70% of laboratory errors.] To be verified during clinical review.
- [SOURCE: CLSI GP41, collection of diagnostic venous blood specimens.] To be verified during clinical review.
- [SOURCE: CLSI GP41 and the applicable patient-identification standard for two-identifier verification and bedside labeling.] To be verified during clinical review.
General references: CLSI GP41 (blood collection), the CLSI order-of-draw standard, Plebani and Bonini reviews on laboratory error, a 2023 specimen-rejection meta-analysis, and CAP Q-Probes. All citations to be verified and finalized during clinical review before publish.