Venipuncture Procedure: Its Significance to Correct Diagnosis of a Patient's Disease

There are several sites of puncture. The most common site is the antecubital fossa consisting of the median cubital vein, the basilic vein and the cephalic vein.

Veins in the scalp, ankles and any suitable site where veins can be found could be utilized.

There are contraindications of venipuncture, like hematoma and on-going seizures; and also complications like syncope, infection with AIDS, hepatitis, thrombosis, and thrombophlebitis, but under a well trained phlebotomists these could be avoided.

What is the significance of venipuncture to correct diagnosis?

1. The correct identification of the patient is essential by the venipuncturist.

Any error in the identification of a patient is a mortal sin in the clinical laboratory. Imagine labeling a blood specimen with the name of another patient. This has serious implications; the patient may be given medications that he does not need.
It is not only important that patients be identified properly; their blood samples should also be labeled correctly with their names on them. Improper identification and mislabeling are serious errors that could cost the life of the patient.

2. The accuracy of test results obtained depends also on the venipuncture procedure performed.

Was a tourniquet used? There are some tests that should not utilize a tourniquet because the use of this would affect the results. Examples of such tests are electrolyte determinations. These substances can shift from the intracellular to the extracellular spaces and could get affected by tourniquet application, flexing the arm and excessive opening and closing of the fists.
A blood sample for blood gas analysis should be collected anaerobically (without the presence of air). If there is exposure of the blood specimen to air during the procedure then inaccuracy of test results would occur.

3. The amount of blood obtained should be appropriate for the determination.

If the venipuncture volume is too much, especially in infants, then it could be detrimental to the health of the baby. On the other hand, if it's too little, then inaccuracy would result. There should be no discrepancy in the procedure as the results could lead to errors in diagnosis which would compromise the health of the patient.

4. Preparation of blood specimens should match the test requested.

The venipuncturist should be aware of the proper specimen that would be needed in the assay; whether it is whole blood, serum or plasma. He should therefore know the type of tests requested. There are certain tests that require anticoagulants like citrate, heparin or ethylenediaminetetraacetic acid (EDTA), etc. These tests include Complete Blood Count (CBC), coagulation tests and many others.

In most cases, in the clinical chemistry and serology sections, serum is needed. Plasma could be used in some enzyme tests.
Serum is the supernatant fluid obtained after clotted blood has been centrifuged and plasma is the supernatant fluid obtained after unclotted blood has been centrifuged.

The correct performance of the venipuncture procedure for each determination is significantly related to the reliability of test results obtained. Its role; therefore, could not be discounted!