Choosing an appropriate sampling method
- Venous blood (obtained by venepuncture) is the specimen of choice for most routine laboratory tests; most laboratory reference ranges are based on venous blood
- Capillary blood sampling may be indicated for paediatric patients where small, but adequate, amounts of blood for laboratory tests can be easily obtained using optimum collection techniques1
- Capillary blood specimens can be advantageous in paediatrics, elderly, severely burned, those with thrombotic tendencies, extremely obese, apprehensive patients and those performing tests at home1
- The smaller volume of blood obtained by capillary sampling is easier to manage in clinics, home settings and remote areas where on-site testing provides quick results for patient diagnosis (Point of Care Testing)1
- Sample type should be taken into account when evaluating results: differences in venous and capillary blood are generally minor, but clinically important differences in some analyte concentrations have been reported1*


EXPERT TIP
There are three different type of blood: arterial (the blood in the arteries), venous (the blood in the veins) and capillary (the blood in the capillary beds, a mixture of arterials and venous blood, obtained by capillary blood sampling)
These materials have been produced in consultation with key opinion leaders and follow global guidelines, but the user should use his or her professional judgement when using any technique or method described in these materials and should take into account all applicable national, regional and institutional guidelines and regulations.
1. Clinical and Laboratory Standards Institute (CLSI) document GP42-A6 (former H04-A6): Procedures and Devices for the Collection of Diagnostic Capillary Blood Specimens; Approved Standard – Sixth Edition. Clinical and Laboratory Standards Institute; Wayne, Pennsylvania, USA: 2008. * Statistically and/or clinically important differences in the concentrations of glucose, potassium, total protein and calcium have been reported1. † Venepuncture in children is often difficult and potentially hazardous; the larger amount of blood removed may pose a danger to children, especially those who are anaemic1. Puncturing deep veins in children may cause painful haematoma, haemorrhage, venous thrombosis, infection, damage to surrounding tissues and other complications1.
Techniques to stimulate the collection of larger capillary blood sample volumes
- The volume of blood required for testing may vary and is dependent upon the specific test being performed and the instrument being used; consult institutional guidelines for the specific volume needed
- Safety lancet gauge and puncture depth, temperature of the puncture site and post-puncture techniques, like massage, can influence the volume of blood collected1
- To achieve a larger volume of blood choose a safety lancet with a thicker gauge and greater puncture depth; consider the age and weight of the patient when selecting the device
- Warming the puncture site may encourage increased blood flow to the area and produce a larger blood sample volume; warming techniques can include asking the patient to rub their hands together or wash their hands in lukewarm water2
- Alternative warming techniques include covering the puncture site with a warming device (commercial device or a warm, moist towel) not to exceed a maximum temperature of 42°C or 107°F2
- After puncture massage gently along the length of the finger towards the tip, using a light squeeze-and-release motion to encourage constant, steady blood flow2*


EXPERT TIP
Pre-warm the puncture site by applying a warming device, not to exceed 42⁰<sup>C</sup>/107⁰<sup>F</sup>, for approximately 3-5 minutes, to increase blood flow without burning the skin<sup>2</sup>
These materials have been produced in consultation with key opinion leaders and follow global guidelines, but the user should use his or her professional judgement when using any technique or method described in these materials and should take into account all applicable national, regional and institutional guidelines and regulations.