How are finger-stick dried Plasma, dried blood spot and venipuncture blood serum different?
Blood collected by conventional venipuncture (blood drawn from veins using a syringe) is centrifuged to separate serum/plasma (the clear liquid part of the blood) in the laboratory and used for testing various biochemical markers including the hormones. The red cells and white cells are removed from the blood so as to be able to measure the total proteins in the blood. Doctors order serum/ plasma protein tests in order to measure the amounts of specific proteins in the blood. Total protein levels may be higher or lower than average in the case of certain health disorders.
Finger-stick dried blood spot is the whole blood collected from the end of the finger by using a small lancet. This is the capillary blood, which is a mixture of red blood cells, white blood cells, and serum/ plasma, in addition to all the nutrients, hormones, and oxygen. Dried blood spot offers ease and convenience of sample collection and many other advantages as opposed to venipuncture blood collection. However, the main disadvantage of using dried blood spot is that since most laboratory reference ranges for blood markers are based on serum/plasma (blood without the white and red cells), it is extremely difficult and almost impossible to get the desired accuracy of test results, thereby producing variation and inconsistency leading to falsely high or falsely low test results for any biochemical marker including the hormones.
Finger-stick dried plasma is the plasma portion of the capillary blood (without white and red cells) collected by a finger prick, which closely resembles the venipuncture blood serum/ plasma. As mentioned above, all the ranges for the biochemical markers to detect and diagnose any disease state are based on the serum/plasma, therefore finger prick dried plasma offers the best of all worlds, which means it offers the ease and convenience of sample collection combined with the accuracy and reliability of conventional serum/plasma testing.