Laboratory:- Part 2 – Common Lab Errors, Effect of various Anticoagulants on Tests
- The handling of the specimens is very important to decrease the error in the lab results.
The most common error in the collection of the samples and reporting are:
- Wrong labeling of the sample.
- The wrong sample of the different patients or not the proper identification of the patient.
- The wrong ratio of the blood and the anticoagulant.
- Not proper mixing of the blood and that may lead to the micro-clots formation.
- Keeping the sample at an extreme (hot) temperature.
- There may be hemolysis which is not a good sample for electrolytes and so many other tests.
- If there is a lipemic serum which will interfere with biochemical reactions.
- Wrong timing of the sample for some special tests like hormones etc.
- Improper centrifugation of the blood which will not give a good clear serum.
- If the sample is not stored at the appropriate temperature.
- Some tests are influenced by the light to the blood, like bilirubin.
- The delayed performance of the tests.
The sample should be rejected when it is found:
- The sample shows hemolysis.
- The serum shows lipemia.
- When there are micro-clots in the blood sample.
- When the sample is too small to perform the test.
- When too much force applied to draw the blood.
- If the specimen is contaminated.
- If the container is leaking.
- Faulty transportation like very hot or cold weather.
- Unlabelled sample.
Effects of various anticoagulants on different tests:
|Inhibit the value
||Decrease the value||Increase the value
||Stimulatory effect||Distort the morphology
|Alkaline phosphatase||Calcium||Sodium||—-||Blood cells|
|—||PT and PTT||—-||—|
|Fluoride||Acid phosphatase||—||Cell morphology|
Precaution before performing the test:
- This is best to perform all the tests within the first 45 minutes to one hour after collection.
- If delayed then properly store the sample at the appropriate temperature.
- The serum is needed for electrophoresis.
- For gases and ammonia whole blood is needed.
- For clinical chemistry, the serum is the best option but plasma may be used.
- For plasma preparation, centrifuge the blood within one hour of sample collection for 10 minutes at 850 to 1000 x gravity.
- Cap the bottle to avoid evaporation.