Sample Rejection Criteria in Laboratory: Table + Register
Sample rejection criteria in the laboratory by sample type: blood, urine, microbiology, histopathology. Register template, rate formula, worked example.
By AvanceZone team · Published 04 Nov 2026 · Updated 04 Nov 2026 · 11 min read
Sample rejection criteria are the written conditions under which a laboratory refuses to test a specimen because the result would be unreliable or could belong to the wrong patient. A good set is specific to each sample type and container, says who may reject and when the doctor must be called first, and is backed by a register so the lab can see which problems keep coming back. This guide gives a criteria table by sample type, the register columns to keep, the rejection-rate formula with a worked example and a checklist to bring the rate down. It is written for Indian pathology labs, but the principles are general.
Starter content. The criteria below are common conventions. Your laboratory's own SOP, reviewed by your pathologist, decides the actual rules; analyzer manufacturers' interference limits and test-specific stability data take precedence.
What are sample rejection criteria and why write them down?
Every lab rejects samples. The difference between a well-run lab and a chaotic one is whether the decision is consistent. If one technician runs a mildly haemolysed potassium and another rejects it, patients get different care for the same sample. Written criteria fix that. They also protect patient safety: an unlabelled tube that is "obviously" Mr Kumar's is exactly how wrong-patient results happen.
ISO 15189, the standard NABL uses to accredit medical laboratories, expects the pre-examination process to be documented: what a correct request and sample look like, how samples are transported and received, and what happens when a sample does not meet the acceptance criteria. In plain words, the lab should have written acceptance and rejection criteria, apply them at receipt, record each rejection and tell the requester. The SOP should also say who decides: a receptionist can reject an unlabelled tube, but rejecting a CSF sample should go to the pathologist.
General rejection criteria for every sample
These apply whatever the test:
- Unlabelled sample. No patient identifier on the container (a label on the bag or the request form is not enough). Reject and recollect.
- Mislabelled or ID mismatch. The name, MRN or barcode on the tube does not match the request. Reject; never relabel at the bench.
- Request–sample mismatch. The test requested needs a different sample or container from the one received (for example, glucose requested on an EDTA tube without fluoride).
- Leaked or broken container. Volume lost, contamination risk for staff and sample.
- Outside stability. Received after the test's stability time at the transport temperature, or with a temperature excursion in transit.
The table: rejection criteria by sample type
The decision column uses three outcomes. Reject: do not test, recollect. Accept with comment: test, but add a comment to the report explaining the limitation. Call doctor first: the sample is hard to replace or the clinical need may justify testing; agree with the requesting doctor before rejecting.
| Sample type / container | Criterion | Why it matters | Decision | Typical recollection instruction |
|---|---|---|---|---|
| Any | Unlabelled container | Wrong-patient result risk | Reject | Recollect; label at the bedside in front of the patient |
| Any | Name/MRN mismatch with request | Wrong-patient result risk | Reject | Recollect; check two identifiers |
| Any | Leaked or broken container | Volume loss, contamination, biosafety | Reject | Recollect in a sealed container |
| Any | Received outside stability time | Analyte degraded or changed | Reject (test-dependent) | Recollect; transport within the stated time |
| Serum/plasma chemistry | Visible haemolysis | Releases potassium, LDH, AST; interferes optically | Reject for affected tests; accept with comment for others | Recollect with correct needle gauge, gentle mixing |
| Serum/plasma chemistry | Gross lipaemia | Optical interference, volume displacement | Accept with comment or reject (test-dependent) | Fasting sample if clinically suitable |
| Serum/plasma chemistry | Icterus | Interferes with some methods | Accept with comment (test-dependent) | Usually none; note on report |
| Serum chemistry | Wrong tube (EDTA for calcium, potassium) | EDTA chelates calcium and adds potassium | Reject | Recollect in the plain/gel tube |
| Serum chemistry | Unseparated serum beyond the stated time | Glucose falls, potassium rises | Reject for affected tests | Centrifuge within the stated time |
| Glucose | No fluoride and delayed analysis | Glycolysis lowers glucose | Reject or accept with comment | Fluoride tube or prompt separation |
| EDTA haematology | Clotted sample | Falsely low counts, platelet clumps | Reject | Recollect; invert 8–10 times immediately |
| EDTA haematology | Insufficient volume (QNS) / under-filled | Excess EDTA shrinks cells, alters indices | Reject | Fill to the line |
| EDTA haematology | Over-filled tube | Inadequate mixing, micro-clots | Accept with comment or reject | Fill to the line |
| EDTA haematology | Aged sample (beyond the lab's limit for smear/indices) | Cell morphology and indices change | Accept with comment for counts; reject for smear | Fresh sample for peripheral smear |
| Citrate coagulation | Wrong blood-to-citrate ratio (under- or over-filled) | Prolongs or shortens PT/APTT | Reject | Fill exactly to the mark |
| Citrate coagulation | Clotted | Consumes factors | Reject | Recollect, clean venepuncture |
| Citrate coagulation | Haemolysed | Activates coagulation, optical interference | Reject | Recollect |
| Urine | Non-sterile or unsuitable container | Contamination, leakage | Reject (culture); accept with comment (routine) | Sterile screw-cap container |
| Urine | Delayed without preservative or refrigeration | Bacteria multiply, cells lyse, glucose falls | Reject for culture; comment for routine | Deliver within the stated time or refrigerate |
| Urine | Insufficient volume | Cannot perform all tests | Accept with comment (priority tests) or reject | Collect the volume stated on the SOP |
| Microbiology | Non-sterile container for culture | Contaminants grow | Reject | Sterile container |
| Microbiology | Delayed transport beyond the SOP limit | Overgrowth or loss of fastidious organisms | Reject, or call doctor first if irreplaceable | Transport within the stated time |
| Microbiology (sputum) | Saliva-like specimen | Upper-airway flora, misleading culture | Reject | Deep cough, early-morning specimen |
| Microbiology (swab) | Swab in wrong or no transport medium, or dried | Organisms die | Reject | Swab in the correct transport medium |
| Microbiology | Repeat culture of the same site within 24 hours (no clinical reason) | Duplicate testing, rarely adds information | Call doctor first | As agreed |
| Histopathology | Unfixed or inadequately fixed tissue | Autolysis, poor morphology | Call doctor first (irreplaceable); fix immediately | Adequate 10 % formalin volume |
| Histopathology | Unlabelled specimen container | Wrong-patient diagnosis | Call doctor first; do not process until identity is confirmed in writing | Label container, not just the lid |
| Histopathology / cytology | Missing requisition or clinical details | Diagnosis needs context | Hold and call | Send the completed requisition |
| Cytology | Air-dried smear where wet fixation is required (Pap) | Staining and morphology poor | Reject or accept with comment | Fix immediately in alcohol |
When not to reject: irreplaceable samples
Some samples cannot be collected again, or only with real harm to the patient: CSF, other body fluids taken by an invasive procedure, biopsies and resection specimens, samples from neonates and small children, and samples taken before a treatment that has since started. For these, the SOP should say "call the doctor first". Often the right answer is to test and add a clear comment, for example "Sample received unrefrigerated after 6 hours; culture result may be affected." The decision and the name of the doctor consulted go into the rejection register even when the sample is tested, so the problem is still counted.
What to do after a rejection
- Record it at once in the register with a standard reason (not free text), the stage at which it was found and who found it.
- Inform the front desk, the collection centre or the requesting doctor, the same day.
- Recollect: create the new sample on the same order with a new barcode, book a home visit if needed, and tell the patient why.
- Track the recollection until the new sample is received, and close the entry.
- Review the register monthly by reason, collector and centre, and act on patterns.
Sample rejection register: columns to keep
A register that can be analysed later needs standard reasons and a few more columns than most paper registers have:
| Column | Example |
|---|---|
| Date and time of rejection | 14-10-2026 09:42 |
| Sample barcode and order number | LS-24311 · ORD2610-00412 |
| Patient (name or MRN) | P100731 |
| Tests affected | Potassium, LDH |
| Reason (standard code) | Haemolysed |
| Stage found | Collection / reception / analysis / validation |
| Collector | Home phlebotomist A |
| Branch or collection centre | Saibaba Colony collection point |
| Rejected by | Technician on the chemistry bench |
| Doctor informed / consulted | Dr. R, 09:55, by phone |
| Recollection status and new barcode | Done 15-10 07:40 · LS-24350 |
Sample data for illustration: an eight-row register from October 2026 might read as follows.
| Date | Barcode | Reason | Stage | Collector | Recollection |
|---|---|---|---|---|---|
| 02 Oct | LS-24102 | Haemolysed | Analysis | Home phlebotomist A | Done |
| 04 Oct | LS-24130 | Clotted (EDTA) | Reception | Front desk | Done |
| 07 Oct | LS-24177 | Haemolysed | Analysis | Home phlebotomist A | Done |
| 09 Oct | LS-24203 | Insufficient volume | Reception | Centre B | Done |
| 12 Oct | LS-24251 | Mislabelled | Reception | Centre B | Done |
| 14 Oct | LS-24311 | Haemolysed | Analysis | Home phlebotomist A | Done |
| 18 Oct | LS-24390 | Delayed transport | Reception | Centre C | Pending |
| 21 Oct | LS-24426 | Clotted (citrate) | Reception | Front desk | Done |
How to calculate the sample rejection rate
The sample rejection rate is the number of rejected samples divided by the number of samples received in the same period, multiplied by 100.
Sample rejection rate (%) = rejected samples ÷ samples received × 100
Worked example (illustrative numbers): a lab receives 3,120 samples in a month and rejects 41. The rejection rate is 41 ÷ 3,120 × 100 = 1.31 %. Now split the 41 by reason: if 28 were haemolysed, haemolysis alone is 28 ÷ 3,120 × 100 = 0.90 %. Split again by collector: if 9 of the 28 came from one collector who collected 260 samples that month, that collector's haemolysis rate is 9 ÷ 260 × 100 = 3.46 %, several times the lab average. The overall rate hides the problem; the breakdown finds it.
Two definitions to fix in your SOP: count samples (tubes or containers), not patients or orders, and count a rejection in the month it happened. Published studies report a range of rejection rates that depends on the lab and on how rejections are defined, for example one haematology study is at PMC9979861; set your own target from your baseline rather than copying a number. The quality indicators page explains how to set targets and lists the related indicators (identification errors per 1,000 samples, samples outside stability, recollection within 24 hours).
How to reduce sample rejections
Group the register by reason and work on the biggest cause first. Common fixes by cause:
- Haemolysis: use an appropriate needle gauge; let alcohol dry before puncture; avoid prolonged tourniquet time; do not force blood through a fine needle or syringe into the tube; invert gently instead of shaking; avoid pneumatic or rough transport. Phlebotomy training has been shown to reduce rejection rates (see PMC5419060).
- Clotted EDTA or citrate: invert immediately and the right number of times; follow the order of draw; do not delay filling a syringe-drawn sample into the tube.
- Insufficient volume and wrong ratio: fill to the line, especially citrate tubes; keep paediatric tubes for small volumes.
- Mislabelling: label at the bedside in front of the patient, with two identifiers, never in advance; print barcode labels from the order.
- Delayed transport: fix courier timings for collection centres; use cool boxes and record the box temperature on the transfer manifest.
- Wrong container: print the tube type on the order and the barcode label; keep a container chart at every collection point.
After each change, watch the next two or three months of the indicator. If the rate does not move, the cause was elsewhere.
How PathLab Software handles rejections
In PathLab Software staff reject a sample from the lab bench, the validation queue or histopathology and cytology receipt by choosing a standard reason (14 starter reasons, editable by your lab) and the stage. If "recollect" is ticked, a new barcode is created on the same order, a home visit is drafted for the next day for home orders, the front desk gets a notification and, if messaging is set up, the patient can receive a short WhatsApp explanation. The rejection register shows the rejection rate, pending recollections, median time to recollect and charts by reason, collector and centre, and it prints and exports to CSV. It is included in every plan; see pricing. The same records feed the pre-analytical indicators on the quality indicators dashboard, and the NABL software checklist covers the other records assessors look for.
Log rejections with standard reasons and see the rate by collector: start a 21-day free trial.
Questions people ask
What are the sample rejection criteria for a blood sample?
Common rejection criteria for blood are an unlabelled or mislabelled tube, the wrong tube for the test, a clotted EDTA or citrate sample, insufficient volume or wrong blood-to-citrate ratio, visible haemolysis for affected tests, and delay beyond the stability time. Your lab's SOP, reviewed by the pathologist, sets the exact rules.
What is sample acceptance and rejection criteria in a laboratory?
Acceptance and rejection criteria are the written rules a lab applies at sample receipt to decide whether a specimen can give a reliable result: correct identification, container, volume, transport time and condition. Samples that fail are rejected and recollected, or tested with a comment when they cannot be replaced, and each case is recorded.
What are the rejection criteria for a urine sample?
A urine sample is commonly rejected if it is unlabelled, in a non-sterile or leaking container (especially for culture), delayed beyond the stated time without refrigeration or preservative, or too small in volume for the tests requested. For routine urine tests some labs test with a comment instead of rejecting.
What are the sample rejection criteria in microbiology?
Microbiology labs commonly reject cultures in non-sterile containers, specimens delayed beyond the transport limit, saliva-like sputum, dried swabs or swabs without transport medium, and unexplained repeats within 24 hours. Irreplaceable samples such as CSF should be discussed with the doctor before rejection.
How do you calculate sample rejection rate?
Sample rejection rate = rejected samples ÷ samples received × 100 for the same period. For example, 41 rejections out of 3,120 samples received is 1.31 %. Break the total down by reason, collector and collection centre to find the cause; PathLab Software shows those breakdowns automatically.
Should a haemolysed sample always be rejected?
No. Haemolysis affects some tests strongly, such as potassium, LDH and AST, and others little. Many labs reject haemolysed samples only for affected tests and report the rest with a comment, using the analyzer's haemolysis index and the manufacturer's interference limits. Your SOP and pathologist decide.
Related guides
Culture and Sensitivity Report Format: Sample and Guide
Culture and sensitivity report format with a full sample: organism, colony count, S/I/R, cascade reporting and how to read it. Urine, pus, blood variants.
Lot to Lot Verification: Formula, Criteria, Worked Example
Lot to lot verification for reagent lots, step by step: how many samples, the formula, acceptance criteria, a worked example and a template you can copy.