Factors affecting the results or processing of Haematology tests

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All sections of Haematology

Test Factor affecting result/processing Outcome
All Tests Failed Specimen Acceptance Policy (Routine samples and Blood Transfusion samples) Would not process
Unlabelled Would not process
Poorly printed label Would not process
Label not straight on sample Would not process
Wrong sample for requested test Would not process
Wrongly labelled Would not process
Sample leaked in transit Would not process (If multiple samples were put in the specimen bag ALL samples would not be processed)
Sample broke in transit Would not process (If multiple samples were put in the specimen bag ALL samples would not be processed)

Coagulation

Test Factor affecting result/processing Outcome
Routine clotting tests Under filled sample Would not process
Routine clotting tests Haemolysis

Would process

Depending on the degree of haemolysis an estimated result may be reported off the analyser with a comment ‘? Validity of result due to haemolysis’

Routine clotting tests Lipaemia

Would process

Depending on the degree of lipaemia an estimated result may be reported off the analyser with a comment ‘? Validity of result due to lipaemia’

All clotting tests Clotted Would not process
Clotting assays Secondary clot in  frozen sample Depending on size of clot would process and add comment ‘? Validity due to secondary clot’ or would not process and add comment ‘Clotted’

Blood counts

Test Factor affecting result/processing Outcome
FBC Small sample
  • Paediatric- minimum required sample volume – 500µl otherwise comment ‘Insufficient’
  • Neonate- minimum required sample volume – 160µL-otherwise comment ‘Insufficient’
  • Adult – minimum required sample volume – 1.5ml- otherwise comment’ Insufficient’
FBC & ESR Small sample
  • Paediatric – separate sample ESR.
  • FBC + ESR requires 2.5ml in FBC tube otherwise will be reported as ‘Insufficient’
FBC & Film Old sample (Greater than 24 hours)
  • FBC would not be processed and comment-‘Too old for analysis’
  • Film would be reported as –‘Too old for morphology’
FBC, ESR & Retic Clotted Sample, or severe case of Cold Agglutination
  • Would not be processed
  • Severe cases of Cold Agglutination the sample must be sent warm (370C) to the laboratory
FBC EDTA may cause clumping of platelets This would result in a falsely low platelet count- laboratory will check a blood film and ask for citrated (Coag) sample to attempt an accurate measurement of the platelets
CSF Contaminated with red cells Would process-appropriate comment will be added
Bone marrow smears Not enough marrow material to perform stains on Could not perform stains – repeats would be requested

Blood transfusion

Test Factor affecting result/processing Outcome
X-Match Samples & Grouping Samples Extreme Haemolysis Would not use – repeats will be requested
Grouping Sample Clotted Sample Would not process
Samples for Cold Agglutinins

Sent to the lab ‘cold’

i.e. not in warm water

Would not process

Haematinics and Haemolytics

Test Factor affecting result/processing Outcome
Ferritin , B12, Serum folate Only EDTA sent Would not process
Haematinic assays Haemolysis Would process and add appropriate comment
Haemolytic assays EDTA clotted Would not process
Plasma Viscosity Sample stored in fridge Would not process
G6PD Assay Temperature during transit Depends on the results from the travel control sample.

G6PD Assay and the testing of travel controls from external sites

When referring tests to MFT we require a completely anonymised sample, that is suspected to be normal but taken under similar circumstances and of similar age to accompany the test samples as a “travel control”. The travel control will only be tested in the event of abnormal results on the patient test samples in order to ascertain that abnormal results are not due to unknown issues which may affect samples during transit. Should the travel control then also show abnormal results the patient test results will be rejected, and a repeat sample requested as it may be assumed that the test results are not reliable due to poor travel conditions. No results will ever be reported on the anonymised travel control.  It is a UKAS requirement that the influence of travel conditions is considered when interpreting results.

This list is not exhaustive – there may be other factors affecting the reporting of results which are not listed

 

(Last reviewed April 2021)