Laboratory:- Part 2 – Common Lab Errors, Effect of various Anticoagulants on Tests

1. The handling of the specimens is critical to decreasing the error in the lab results.

There are the following areas where the  mistake can lead to erroneous laboratory results:

1. Specimen collection:
   1. Wrong techniques of blood collection like too much pressure on the blood collection area.
   2. Blood is put into the wrong test tubes for serum blood put into the test tube containing anticoagulant.
   3. The blood sample was wrongly labeled.
2. Patients preparation:
   1. Blood was collected at the wrong time.
   2. If a blood sample needed a fasting sample and collected at a random time.
   3. There is a diurnal variation in the various blood samples. You may collect a sample at the peak level.
3. Specimen handling:
   1. If the blood sample is delayed for the transfer to the lab.
   2. A blood sample is stored at the wrong temperature.
   3. did not properly process the blood sample.
4. Chemical analysis:
   1. They are not following quality control rules.
   2. They are not following the protocol of the test procedure.
   3. There will be a difference in manual and automation.
5. Reporting of the result:
   1. Mistakes in the calculation of the result.
6. The difference in reporting the result on phone and on paper.

Indications for ordering laboratory tests:

1. To confirm a clinical impression or to make a diagnosis.
2. To rule out diagnosis or disease.
3. To follow for the prognosis of the disease.
4. To help in the therapy of various diseases.
5. For the screening of the disease in the population.

The most common error in the collection of the samples and reporting are:

1. Wrong labeling of the sample.
2. The technique of the blood sample:
   1. This is very important to follow an excellent technique to collect good quality blood.
   2. If you apply tourniquet for a longer time, that will lead to acidosis and hemoconcentration.
3. The wrong sample of the different patients or not the proper identification of the patient.
4. The wrong ratio of the blood and the anticoagulant.
5. Not proper mixing of the blood, and that may lead to the micro-clots formation.
6. Keeping the sample at an extreme (hot) temperature.
7. There may be hemolysis, which is not a good sample for electrolytes and so many other tests.
   1. Try to collect an adequate blood sample and avoid microclots.
8. If there is a lipemic serum which will interfere with biochemical reactions.
9. Wrong timing of the sample for some special tests like hormones etc.
   1. If a blood sample is taken after the food ingestion, then:
      1. The glucose level will be high.
      2. Will raise triglyceride.
      3. will rais lipid fractions.
10. Improper centrifugation of the blood which will not give a good clear serum.
11. If the sample is not stored at the appropriate temperature.
12. Some tests are influenced by the light to the blood, like bilirubin.
13. The delayed performance of the tests.
14. Human errors can also account for the laboratory variation. This depends upon the performance of testing.
    1. This can be minimized by automation.
15. There will be mistakes if:
    1. Selecting a specimen to analyze from the wrong patient.
    2. There are transcriptional errors.
    3. There are any mistakes along the whole chain of collecting, processing, analyzing, and reporting.

The sample should be rejected when it is found:

1. The sample shows hemolysis.
2. The serum shows lipemia.
   

   Serum appearance in hemolysis and lipemia

3. When there are micro-clots in the blood sample.
4. When the sample is too small to perform the test.
5. When too much force applied to draw the blood.
6. If the specimen is contaminated.
7. If the container is leaking.
8. Faulty transportation like very hot or cold weather.
9. Unlabelled sample.

Effects of various anticoagulants on different tests:

Anticoagulants	Inhibit the value	Decrease the value	Increase the value	Stimulatory effect	Distort the morphology
Oxalate	Inhibit	Decrease	Increase	Stimulate	Distort
	Alkaline phosphatase	Calcium	Sodium	—-	Blood cells
	Acid phosphatase	—-	Potassium	—-	—
	LDH	—-	—-	—-	—
	Amylase	—	—-	—	—
Citrate	SGPT	Amylase	Sodium	Acid phosphatase	—
	SGOT	Calcium	Potassium	—-	—
	Alkaline phosphatase	—-	—-	—-	—
EDTA	Creatine Kinase	Calcium	PT	—-	—
	Alkaline phosphatase	Iron	PTT	—-	—
		platelet aggregation	Sodium	—-	—
		—	Potassium	—-	—
Heparin		—	T 3	—-	—
		—	Thyroxine	—-	—
		—	PT and PTT	—-	—
		—	Lithium	—-	—
		—	Sodium	—-	—
Fluoride		Acid phosphatase	—		Cell morphology
		Alkaline phosphatase	—
		SGPT	—
		SGOT	—
		Creatine kinase	—
		Amylase

Precaution before performing the test:

1. This is best to perform all the tests within the first 45 minutes to one hour after collection.
2. If delayed then correctly store the sample at the appropriate temperature.
3. The serum is needed for electrophoresis.
4. For gases and ammonia, whole blood is needed.
5. For clinical chemistry, the serum is the best option, but plasma may be used.
6. For plasma preparation, centrifuge the blood within one hour of sample collection for 10 minutes at 850 to 1000 x gravity.
7. Cap the bottle to avoid evaporation.

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