In order to have smooth home diagnostic tests such as self-monitoring of blood glucose by a person with diabetes, a need was felt for simple blood for sample blood collection procedures that could be performed in any setting. The collection of capillary blood from a fingertip quickly evolved as the standard sampling methodology. It is performed in homes and in hospitals for monitoring purposes that require relatively small samples of blood. It is more cost effective, less traumatic and more convenient to obtain a blood sample by lancing the skin capillaries than it is by using a phlebotomist to draw a tube of venous blood.
Capillary blood glucose testing is used for the care of people with diabetes as a monitoring tool giving a guide to blood glucose levels at a specific moment in time. Capillary blood glucose monitoring was first established in 1970s. Since then the technology and design of the meters have increased almost beyond recognition.
Blood glucose levels are measured by a meter to do use capillary blood directly from fingersticks.
Most POCT samples are capillary blood in origin. However, irrespective of the type of buiological specimen collected - whether blood, urine, stool, wound swab, blood cultures, the lab results will be only as good as the quality of the collected sample.
There is a large variation in the ability of lab staff members to collect capillary blood samples since some are experts and some are not at all. As usual, with a skill, practice makes perfect. The common sources of errors are like shallow skin puncture leading to a slow blood flow, failure to wipe away the first drop of blood, squeezing too hard, scopping blood along the skin as it dribbles from the puncture site.
There are three Golden Rules for successful capillary blood sample collecting viz. 1) Make sure the blood is flowing freely from a clean, warm, dry puncture site; 2) Always wipe away the first drop of blood (except for haemostasis testing) and 3) Squeeze slowly and rhythmically, gripping the digit firmly between the base of thumb and first finger. This will allow a good solid squeeze without hurting the patient or rupturing red cells. One has to be very careful and donot burn the patient as young skin is sensitive and make sure all skin is clean and dry before you start collecting your sample.