Venipuncture is the extraction of blood from the vein by using a syringe and a needle, while capillary puncture, also know as “finger stick”, is the collection of blood by puncturing the palmar surfaces of the fingers, ear lobes, big toe (in infants,) with the use of a lancet and a capillary tube or an appropriate specimen holder.
These are both methods of specimen collection, but there are advantages of each method over the other. They are used according to the specimen requirements and depending upon the amount of blood specimen needed for the laboratory test.
The following are advantages of venipuncture over capillary puncture:
1. Venipuncture allows the collection of more volume of blood because multiple collections could be done. The patient’s condition should be considered however; if there is no danger to the patient and several tests are required, then multiple tubes maybe collected. A single puncture with multiple tubes would avoid repeated performance of the procedure. For infants, the capillary stick is preferred because large specimen collections are not advisable as this may cause a decrease in the total blood volume of the infant.
Capillary puncture on the other hand, will be inappropriate for multiple tubes as blood specimen would only come from the capillaries, while that of venipuncture is from the veins.
2. Venipuncture allows you to store blood for future and additional testing because vacutainer tubes could be used, while capillary could only store very little volumes.
3. Although a big needle is used in venipuncture when done properly, it is less painful than capillary stick. This is because there are more nerve endings in the puncture sites for capillary puncture.
4. There are some special tests which could only be performed on a venous collection.
5. Venipuncture allows more options with regards to site selection. Suitable veins could be found all over the body. Exceptions are seen in obese and burnt patients.
6. Venous blood yield more dependable results as the specimen comes directly from the circulation.
It would also be noteworthy to mention the disadvantages of venipuncture:
1. To avoid complications, it should only be performed by a skilled phlebotomist.
2. It is difficult to perform on obese patients and victims of severe burns, because veins are not visible and could not be palpated.
Whatever the method of specimen collection you decide to use, the observation of the correct procedure and awareness of the precautions would contribute significantly to the reliability of results. The patient’s welfare should be foremost in your mind – as the clinical laboratory scientist or medical technologist. And this could only start with the proper venipuncture procedures.