Blood samples that should be discarded

• Whenever you find the following possibilities, reject the sample, and try to get another fresh sample.

Samples to be rejected are:

 Hemolyzed sample:

1. Serum shows evidence of hemolysis when the hemoglobin is >20 G/dL.
2. Slight hemolysis does not affect most of the test values.
3. Severe hemolysis causes a dilutional effect on those constituents, with a lower concentration in the RBCs than the plasma.
4. There will be a marked effect of those parameters present in high RBC concentrations than in the plasma.
5. Hemolysis will increase the value of:
   1. Aldolase.
   2. Lactate dehydrogenase (LDH).
   3. Total acid phosphatase.
   4. Magnesium.
   5. Potassium.
   6. Phosphate.

6. How to prevent hemolysis:

   1. Make sure that the syringe and the needles are dry.
   2. Plastic disposable syringes are preferred.
   3. Avoid rough handling of the blood. Handle carefully and gently the blood sample.
   4. Remove the needle and then eject the blood into the tube. Blood through the needle will leads to hemolysis.
   5. Mix the anticoagulant gently and try to b not rough.
   6. Gently transfer the blood and avoid frothing of the blood sample.
   7. Before taking blood, be sure that the skin is dry.
   8. If you apply sterile petroleum on the heel, it will avoid the spreading of the blood.
   9. Collection of the heel prick blood, when collected in a heparinized plastic tube or a siliconized glass tube, will prevent hemolysis.
   10. In case of delay  (1 to 3 hours), store the blood in the fridge at 4 °C to 10 °C.
   11. If there is the possibility of cold agglutinins, store the blood at 37 °C in a water bath.
   12. Avoid freezing of blood because, on thawing, RBCs will lead to hemolysis.
   13. Hypotonic solutions will hemolyze the blood, so try to prepare the isotonic solution.

Lipemic serum:

1. Serum with lipemic appearance  will affect chemistry tests like:
   1. Phosphorus.
   2. Creatinine.
   3. Total protein.
   4. Calcium.
   5. ALT (Alanine aminotransferase).
      1. Ultracentrifugation can remove the effect of lipemia.

Blood samples That should be Discarded (Samples to be rejected):

1. The sample for CBC is unsuitable if there are clots and is hemolyzed.
   1. If there are microclots are not suitable for Cell counting, it will give a low count.
2. If there is an insufficient blood sample.
3. If the sample is not labeled.
4. If there is a discrepancy between the sample and the request form.
5. If the blood sample is insufficient in quantity.
6. Poor handling of the sample when there is the effect of light.
7. The sample was collected at the wrong time.
8. If there is the contamination of the sample.

Changes in the  blood/serum when the vein is pressurized too much:

1. Most of the time, the tourniquet puts pressure on the vein to make it prominent.
2. When a blood pressure cuff is used, the pressure is mostly  ∼60 mm Hg.
3. Never leave the velcro pressure cuff for more than one minute; it will change the blood chemistry even with a shorter period of time.

If the cuff is applied for 1 to 3 minutes, it will lead to blood chemistry changes:

Parameters	Increase in concentration	Decrease in concentration
Potassium		6.2%
Bilirubin	8.4%
Cholesterol	5.1%
Total lipid	4.7%
Total protein	4.9%
AST (SGOT)	9.3%
Iron	6.7%

Blood sample’s importance:

1. The blood sample near the tourniquet has the same composition as the circulating blood.
2. So use the first sample for the critical values like serum calcium.
3. The first tube may show a 5% increase in the protein level, while the third tube shows a 10% change.
4. In the case of slight trauma to the skin may increase the enzymes (SGOT).
5. In the case of stress, the patient will increase the growth hormone and cortisol.

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