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Sample rejection criteria


Sometimes tests cannot be performed in the laboratory if samples fall short of the quality, volume or other eligibility criteria such as clear sample labelling. In these cases, the potential risk to the patient management is that the laboratory may need to reject the samples, and not carry out processing. Sometimes the laboratory can rectify a situation where a sample falls short of the sample acceptance criteria though in this case the risk to the patient management may be a breach of stated turnaround time and a delay to provision of the result. In order to reduce the risk of sample rejection or delay to provision of results, please ensure all sample taking criteria are met.

Summary list for sample rejection

  • Incorrect sample types received:
    • Basic incorrect blood tube/other sample.
    • Samples without the appropriate preservative (e.g. acidified urine samples).
    • Samples that are received ambient, when a frozen sample is required.
    • Samples that are received unprotected from light, when they are required to be covered at the point of venepuncture.
    • Samples in incorrect containers (e.g. cervical cytology must be a ThinPrep vial; urine cytology must be in a uricyte container).
  • Insufficient sample received.
  • No sample received.
  • Labelling or form issues (mislabelled / unlabelled / no forms / no clinical information).
  • Clotted / haemolysed / lipaemic / icteric samples. Sample is broken or has leaked in transit.
  • Stability time has been exceeded. Stability time is test-dependent, and also refers to tests that can only be carried out on certain days of the week.
  • Sample contamination (e.g. being in the same bag as a leaking sample):
    Samples are high risk or infectious. Samples that are received in expired tubes.

Samples deemed to be precious (e.g. CSF, fluid, tissue, bone marrow and paediatric samples) will not be discarded by the laboratory. Results will include a comment relating to the condition of the sample (e.g. sample unlabelled).

Department-specific list for sample rejection

Sample Reception will not accept samples packaged with needles of any kind.

Biochemistry cannot accept:

  • previously frozen samples that have thawed in transit.
  • samples that display antibody interference.
  • samples that have had separation delays/un-centrifuged samples that have been stored in the fridge.
  • paraprotein resulting in viscous samples.
  • CSF protein that is blood-stained.

Cervical Cytology cannot accept:

  • over- or under-filled samples for testing.
  • samples received within three months of the previous test in order to allow epithelial cells to regenerate.

Coagulation cannot accept:

  • over- or under-filled samples for testing.
  • previously frozen samples that have thawed in transit.

Haematology cannot accept frozen whole blood for testing.

Microbiology cannot accept samples in non-sterile containers or in formalin.

Molecular Pathology cannot accept samples for haemophilia testing without informed consent.

Parasitology cannot accept TBQ kits that:

  • Incorrect sample types: Plasma instead of serum or EDTA blood for most serology tests; blood samples other than citrate blood for Microfilarial microscopy; blood samples other than EDTA blood for malaria microscopy and PCR; peripheral blood for Leishmania microscopy and PCR.
  • Samples that have been incorrectly stored/ treated: Refrigerated stool sample for stool culture; fixed sample for Leishmania culture (PCR will be performed); fixed sample for stool PCR (Microscopy will be performed).
  • Insufficient sample volume (especially for Strongyloides culture, which requires around 20ml of stool)
  • Samples whose delivery is delayed beyond viable processing time: 15 minutes for hot stool samples; 24 hours for Trypanosomal blood microscopy.