Blood Tests and Point Of Care diagnostics

Blood testing

Blood carries out many vital functions as it circulates through the body. It transports oxygen from the lungs to other body tissues and carries away carbon dioxide. It carries nutrients from the digestive system to the cells of the body, and carries away wastes. Blood helps our body fight off pathogens and toxins, helps our body heal with its clotting ability, and regulates our body temperature.

Doctors rely on many different laboratory tests of blood to diagnose and monitor diseases. Some tests measure the components of blood itself, and others examine substances found in the blood stream to determine how other organs are functioning.

A CBC (complete blood cell count) is the most commonly performed blood test. It measures the two major basic components of blood: plasma, which is the clear, straw-coloured liquid portion, and red blood cells, white blood cells and platelets, which help in clotting. Red blood cells carry oxygen from the lungs to the tissues and carbon dioxide away. White blood cells help the body fight infection. In addition to determining the number of blood cells and platelets, the percentage of each type of white blood cell, and the content of haemoglobin (protein found in red blood cells), the CBC usually assesses the size and shape of red blood cells.

A test to measure the percentage of red blood cells can be done by a nurse or medical technician, or phlebotomist quickly and simply.

Blood samples may also be drawn from a vein, usually in the forearm. The puncture site is cleaned with an antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to restrict blood flow through the vein. This causes the vein below the tourniquet to fill with blood. A needle is inserted into the vein, and the blood is collected in a vial or syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

When a blood test is performed on an infant or child, a small amount of blood can be taken from the finger or earlobe.

Normal red blood cell counts vary, depending on the type of sample and your age and gender: Haemoglobin concentration correlates closely with the red blood cell count. Normal white blood cell counts range from 4,000 to 10,000 white blood cells per cubic millimetre of whole blood.

A low red blood cell or haemoglobin count may indicate anaemia, or severe bleeding. An elevated red cell or haemoglobin count may indicate polycythaemia, a rare blood disorder. Red blood cells that are abnormally shaped can also signal problems: sickle-shaped are characteristic of sickle cell disease, small red blood cells may indicate early iron deficiency, and large oval red blood cells suggest folic acid or vitamins B12 deficiency (pernicious anaemia).

The number of white blood cells may increase or decrease significantly in certain diseases. An elevated white blood cell count often indicates infection, such as an abscess, meningitis, appendicitis, or tonsillitis. A high count may also be caused by leukaemia or by dead tissue from burns, heart attack, or gangrene. A low white blood cell count indicates bone marrow problems.

Point of Care Diagnostics (PoC) is a method of near patient testing for pathology tests. Many devices are now available to carry out testing at the 'point of care'. I.e. On the ward, in A&E etc.

Point of care diagnostics can integrate biochemical testing alongside physiologic measurements. Blood Analysis can be carried out by the patient's bedside very quickly, and using low blood sample amounts. POC may deliver results for blood gases, electrolytes, chemistries, haematocrit, and other calculated parameters.

Some Blood Analysis Portals use disposable cartridges containing the same technology as large, laboratory benchtop equipment, only in miniature. Immediacy of diagnostics test information is essential for precise titration and, ultimately, for improved therapy in adult, paediatric, and neonatal intensive care; operating theatre and post-anaesthesia; and emergency settings - environments where patient care commands immediate turnaround of blood test results for clinical decision making. Yet, traditional stat blood testing processes experience inherent delays from the time a physician orders tests until results are delivered. With POC testing, neither the sample nor the caregiver leaves the patient's side.