Why labs reject specimens

A specimen that arrives at the lab in poor condition produces unreliable results. Rather than report an inaccurate value that could mislead clinical care, the lab rejects the specimen and requests a redraw. The rejection protects the patient — at the cost of another needle stick.

The PBT exam tests the rejection criteria because understanding them helps the phlebotomist avoid them on the next draw.

Common rejection criteria

1. Misidentification. The label does not match the requisition, or the patient identifier is missing or incorrect. This is the most serious rejection — a specimen from the wrong patient can lead to catastrophic clinical decisions.

2. Hemolysis. Visibly pink or red serum/plasma, or hemolysis index above the lab's threshold. Affects potassium, LDH, AST, ALT, bilirubin, and many other tests.

3. Insufficient volume. The tube is not filled to the minimum required volume (e.g., 90 percent for citrate, the indicator line for EDTA microtainers). The anticoagulant:blood ratio is wrong.

4. Wrong tube. The specimen was collected in the wrong additive for the test (e.g., EDTA collected for a serum chemistry test).

5. Clotted anticoagulant tube. The tube contains an anticoagulant but has clotted — usually because of inadequate mixing, expired tube, or slow collection.

6. Improper handling. Specimen was not transported at the correct temperature, was held too long before analysis, or was exposed to light when the test is light-sensitive (e.g., bilirubin).

7. Lipemia. Severe lipemia (fat in the specimen) from recent fatty meal can interfere with some tests. Sometimes rejection, sometimes interfering with analysis.

8. Contamination. IV fluid contamination from drawing proximal to an IV site. The lab may detect this by unexpected sodium, glucose, or other analyte values.

9. Expired tube. Tubes past their expiration date may have lost vacuum or have degraded additives.

10. Broken or leaking specimen. Cracked tube, leaking stopper, or damaged container.

11. No requisition. Specimen arrives without a test requisition or with mismatched information.

12. No label. Unlabeled specimen. Most labs treat unlabeled as the highest-risk rejection.

The corrective action

When the lab rejects a specimen, the corrective action is typically:

• Redraw the specimen with proper technique.
• Document the rejection — what was wrong, why it was rejected, who decided to reject.
• Notify the clinician that the result is delayed and a redraw is needed.
• Identify the cause — was it a phlebotomist error, a patient issue, or a process issue?
• Adjust the process — retraining, equipment change, or technique adjustment to prevent recurrence.

The exam tests whether the candidate knows that the appropriate response to a rejection is a redraw with corrected technique.

How labs document rejections

The lab's rejection log typically includes:

• Patient identifier — who was the specimen from.
• Date and time — when the specimen was received.
• Reason for rejection — which criterion.
• Specimen condition — hemolysis, clotting, volume, etc.
• Collector information — who drew it (for tracking training needs).
• Requisition — which tests were ordered.
• Outcome — redraw, cancellation, or alternative testing.

The rejection log is reviewed by the lab supervisor and shared with the phlebotomy team for quality improvement.

How to minimize rejections

Phlebotomist-controlled practices:

• Verify identification before the draw.
• Use the correct tube for the test, in the correct order.
• Fill tubes to the specified volume.
• Mix gently immediately after collection.
• Label at the bedside with the correct patient identifiers.
• Transport appropriately — temperature, time.
• Check tubes for expiration before use.

Each practice reduces the rejection rate. High-performing phlebotomy teams have rejection rates below 2 percent; underperforming teams can be above 10 percent.

Special considerations

Blood cultures. Mislabeled blood cultures are typically not rejected — they are reported to the clinician with a caveat. The culture is processed, but the result is flagged as having been drawn without proper identification. This protects against false-negative reporting while informing the clinician.

Coagulation specimens. The 90 percent fill rule is strictest for citrate. Underfilled tubes are rejected because the result is unreliable.

Glucose specimens. Gray-top fluoride tubes inhibit glycolysis, allowing delayed analysis. If a fluoride tube is not used, the specimen must be delivered to the lab within 30 minutes or the result will be falsely low.

Light-sensitive tests (bilirubin, vitamin B12, folate). Specimens must be protected from light during transport. Wrapping the tube in foil or using amber-colored tubes prevents light-induced degradation.

Common exam traps

1. Believing the lab should report an inaccurate result rather than reject. The lab's role is to provide accurate results. Rejection is appropriate when the specimen cannot produce an accurate result.

2. Confusing hemolysis with normal red serum. Hemolyzed serum is bright pink/red, distinct from the pale yellow of normal serum.

3. Believing "small clot" in an EDTA tube is acceptable. Any clot in an anticoagulant tube invalidates the result. The specimen must be rejected.

4. Confusing rejection with recollection. Rejection means the lab will not test the current specimen. Recollection (redraw) is the corrective action.

5. Believing the phlebotomist can overrule the lab's rejection. The lab makes the rejection decision based on its own criteria. The phlebotomist's role is to redraw properly.

The exam's favorite rejection questions

Question type 1: "Which of the following is a reason for specimen rejection?" — Answer options typically include hemolysis, clotted anticoagulant tube, misidentification, and improper handling. Any of these is acceptable.

Question type 2: "A lavender-top tube arrives at the lab with a small clot. What is the appropriate action?" — Answer: reject. Clots in anticoagulant tubes indicate insufficient mixing or expired tube; the result is unreliable.

Question type 3: "A citrate tube is filled to 75 percent. What happens?" — Answer: reject. The 90 percent rule applies; underfilled citrate tubes produce falsely prolonged PT/PTT.

A practical closing note

Rejection is a feedback signal. Every rejection tells the phlebotomy team something went wrong — and gives them the chance to fix the system. Track your rejection rate; if it is above 2 percent, look at the patterns and adjust. The exam rewards the candidate who knows the criteria and the corrective action.