Saturday, September 24, 2011

Blood Testing- An Explanation


 I thought it might be a good idea to have some more details about blood tests. I discovered the following on the Fifty-Plus website. I have actually learned quite a bit from this, so for anyone else in a similar situation to me, you may also find it of use.

Having a blood test is not something any of us particularly want to have done,  it usually means that something isn’t quite right and the doctors need to find out what it is. Finding out what is wrong is all well and good but, did you understand what the doctor said to you as to why you are having, for instance your fasting blood test done?  The idea of this section is to try and explain in laymen’s terms what the doctor is looking for, however I do need to highlight:-

A)   This blood test information is for general purposes only and should not be taken in isolation. If you have a health condition which concerns you then you should discuss your symptoms with your doctor.

B)   The clinical ranges for what is stated as normal given here are typical figures. Different laboratories sometimes use slightly different ranges depending on how they work. Blood test results need to be interpreted by qualified healthcare professionals in combination with further investigations.

The Procedure for your Blood Test
In some surgeries or medical centers a doctor or nurse may take the blood sample, but quite often you are given an appointment to attend your local hospital to the Haematology (blood) department. This is where trained phlebotomy staff will take all the blood samples requested, this is sometimes more convenient as the blood sample can be transferred straight to the hospital laboratory .This will mean the blood analysis will be done promptly and the blood test results returned to your doctor more quickly. Blood analysis is undertaken by trained staff with the results being interpreted by your doctor with all your clinical notes to hand. Sometimes people can look at which blood sample is being taken and become anxious, often this blood test is being done to exclude conditions.

A trained phlebotomist.-(a specialised clinical support worker) will take a small blood sample usually from a vein near the inside of your elbow, if that is not possible they may take blood from the wrist. These sites are usually chosen as the veins run fairly close to the skin surface making them more easily accessible.

Occasionally people have a fear of needles or of blood or both and can feel faint at both the prospect of the blood test and the procedure itself. If you don’t want to end up on the floor let the phlebotomy staff know and they will be able to position you correctly. If you are taking any blood thinning medication ensure you have discussed this with your doctor prior to your blood being taken, otherwise you may have problems clotting and end up with a rather large bruise.

*The phlebotomy specialist will either wash their hands or use a medical hand disinfectant or wear gloves for the procedure.

* You will be asked if you have any allergies to adhesive dressings or latex, as sometimes the gloves used by the phlebotomy staff are latex.

* The arm chosen will usually be opposite the one you write with to reduce discomfort. A tourniquet will be placed around the upper part of your arm, this will be pulled fairly tight to reduce the blood flow causing the veins in your arm to swell this makes it easier to locate the vein.

* The area is wiped with an antiseptic wipe to reduce the potential germs on your skin surface (everybody has them) they will wait for this to dry; this is done to reduce the chance of introducing a skin contaminant.

* The needle will then be inserted through the skin to the vein this is like a pricking sensation it will not hurt excessively.

* If you are having a fasting blood test you may have a “cannula” or “butterfly” placed in the back of your hand and secured with adhesive tape or a dressing. It will be explained to you that as you will be having blood taken over a period of time, this method will reduce the need for repeated insertions of a needle.

* The blood will be extracted using either a syringe with a needle, or more commonly a needle attached to a plastic device where different vacuum vials-(small bottles). These can be connected allowing a small amount of blood into each vial for a variety of different blood tests, hence the different colour vials.

* The needle will be removed and a small spot plaster put on the site to reduce the chance of infection. The phlebotomist will press on the site for a couple of minutes or ask you to, to reduce the chance of a bruise.  If the site becomes inflamed, red and sore you will need to visit your doctor for advice.

* If you have been lying down for the blood test you will need to sit up slowly.

* The blood sample will be carefully labeled with your personal details and stored correctly by the phlebotomy staff.

* The blood samples will then be sent to the laboratory for blood analysis.

* The results of your blood test will be sent to your Doctor, you will then be asked to come in to discuss the results. When blood test results are explained to you it is a good idea to write down what is said or take a friend or family member with you if you don’t think you will remember what is said.  If you are expecting blood test results of a sensitive nature for instance the HIV test, counsellors will be available to you.

Blood Tests
A blood sample will be taken as part of an investigation into your condition for a variety of reasons:-
To see if there is any damage to any of the organs in your body
To see if you have an infection
To see if you have diabetes
To check your thyroid is working correctly
To measure levels of a variety of different chemicals, like enzymes electrolytes or oxygen and carbon dioxide in your blood
To check your blood gas levels – imbalances can be indicators of possible respiratory (breathing) or metabolic (energy processes) problems
To check your blood group type
Genetic/DNA testing which tells you if you have inherited a condition or if there is a gene mutation which may result in a condition or syndrome which can affect your health
To check your cholesterol levels
To check that your liver is functioning properly if it not it will produce enzymes which can be detected

Blood is made up of two primary elements:
The fluid –This is called Plasma. This fluid is principally made up of water and supplies all the nutrients, proteins and hormones your body requires to remain healthy.
Cells –there are three kinds of cells that circulate constantly around your body
Red blood cells- deliver oxygen around the body – your whole body is a network of veins arteries and capillaries, which carries oxygen from your lungs around your body and exchanges it for carbon dioxide which they dispose of.
White blood cells- leukocytes –These make up part of your body’s defense system  / immune system respond to  infection
Platelets- These are the cells which form blood clots if you cut yourself

Blood Test Abbreviations
Below is a list of some of the blood tests which are most commonly taken with the abbreviations used and a very short explanation what the blood sample may be being taken for. Many of the blood tests do not require you to fast however for some specific ones you may be given instructions from your health care provider to restrict fluids, medication or diet. If you are in any doubt ask for advice as it can be very frustrating turning up for an appointment and not being able to have the blood sample taken. Many of the blood test results explained will need further consultation with your health care provider.
Albumin – This is the main protein which is in blood. low levels can indicate certain types of chronic illnesses such as liver disorders
Elecs / U&E’s Urea and Electrolytes – This is done to assess your Electrolyte (minerals) levels There are three main electrolytes that can be measured with an electrolyte test, sodium, potassium and chloride. The test will show how well your kidneys are working
Ferritin – A protein – This is to check the levels are correct as they are important for red blood cell production, and the levels of iron stored in your body.
Normal range is:-
Male: 12-300 ng/mL –
Female: 12-150 ng/mL – nanograms per milliliter
(HCT) Haematocrit – This is a measure of thickness, viscosity, of red blood cell content called Packed Cell Volume PCV of your blood
(HbA1c) -Haemoglobin A1c – This measures the glycated haemoglobin which is where the glucose has attached it self to red blood it is often used to measure your management of your diabetes.
Normal levels are HbA1c of 6% or less
LDH – Lactate Dehydrogenase – This is an enzyme if the levels are raised this can indicate damage to cells and tissue. It is also used to monitor progress
LDL – Low density lipoprotein – Cholesterol – this is the “bad” cholesterol – it is protein which carries cholesterol to the arteries and blood vessels causing build up and blockages this can cause a heart attack or stroke
Magnesium – A deficiency in this basic element of the blood can be due to difficulties with absorption which can be due to medication, intestinal problems or heart disease. High levels may be due to kidney failure  
ALT- Alanine aminotransferase – This is an enzyme and the test is performed to check to see if you have a liver problem
Amylase – This is an enzyme and if the levels are raised this may indicate a problem possibly pancreatitis (the pancreas is important for secreting enzymes for digestion and regulating blood sugar levels with the hormone insulin)
(BNP) Beta-Natriuretic Peptide – This can be done to check fluid in your lungs and for deteriorating heart disease
(BUN) Blood Urea Nitrogen - This test is performed to assess the levels which if raised may indicate renal function impairment. If it is low it can indicate liver failure amongst other conditions
B12 and Folate – This is done to diagnose the cause of anaemia or nerve damage- Neuropathy
Calcium – Is found in bone and blood calcium is tested to monitor how much is circulating and affecting conditions of the heart, nerves and kidneys as well as bones and teeth
Card EnzCardiac Enzymes – This test is performed when a heart attack is suspected
Chol CholesterolLipid profile – This is to test if you have heart disease or circulatory problems this is a common test which is offered to people who have family history of high blood pressure or if you are Plus Fifty years old – high levels need to be treated otherwise you may be at risk of heart disease or a stroke. You will be told not eat anything and only drink water for 10-12 hours before having your blood sample taken.
There are different types of blood cholesterol tests, when combined they are referred to as a lipid profile.
good - (HDL) cholesterol
bad - (LDL) cholesterol
total cholesterol
triglycerides (other fatty substances)
Chloride – This is important for nerve and muscle function and distinct variations may indicate disease
Creatinine – This is a waste product and high levels can possibly indicate further tests will need to be undertaken to rule out poor kidney function
ESR Blood TestErythrocyte Sedimentation Rate – This screens for infection and monitors inflammation.
 Normal results are :-
Men under 50 years old: less than 15 mm/hr
Men over 50 years old: less than 20 mm/hr
Women under 50 years old: less than 20 mm/hr
Women over 50 years old: less than 30 mm/hr
FBC Blood Test  – Full Blood Count / Blood Count – This is done to check your general health and to screen for disorders, such as anaemia, infection, and nutrition
Normal levels are:
Haemoglobin  

adult males 13.5-17.50 g/dL
adult females 11.5-16.5 g/dL  
Red cell count  
adult males is 4.5-6.5 x 1012/L
adult females 3.8-5.8 x 1012/L
Haematocrit  
adult males is 0.40-0.50  
adult females 0.37-0.47  
MCV (
Mean cell volume) range for adults is 76-100 fL
MCH (
Mean cell haemoglobin) range for adults is 27-32 pg, and the normal  
MCHC (Mean cell haemoglobin concentration) range is 31-36 g/L
White cell count for adults is 4.0-10.0 x 109/L
The different types of white cells in adults are:
Basophils: 0.05-0.1 x 109/L
Eosinophils: 0.02-0.4 x 109/L
Lymphocytes: 1.0-3.5 x 109/L
Monocytes: 0.2-1.0 x 109/L
Neutrophils:2.0-7.5×109/L

Platelet count for adults is 150-450 x 109/L

 · FSHFollicle Stimulation Hormone – This is done to check your pituitary gland which regulates the hormones, along with the trigger for your ovaries to prepare to release an egg · GGT – Gamma-Glutamyl Transferase test - This is an enzyme which is utilized in muscle, liver and heart function if this is raised it may indicate that disease is affecting these organs You will be told to not eat for at least eight hours before the test and not drink alcohol for 24 hours before the test. Smoking can also affect the test results.
 
 · Globulin - These are proteins you will need to prepare for the test by not eating for four hours prior to the blood being taken. It is important to discuss with your doctor any medication you are taking prior to the test. The results will help with the diagnosis of immunoglobulin disorders
 · Glucose Blood Test Fasting Blood Test – This checks the levels of plasma glucose in your blood. For an initial reading you may have to fast (stop eating) for up to 12 hours/ overnight before the bloods are taken. If you have diabetes you can monitor your own levels.
The ideal values are: 4 to 7mmol/l before meals: less than 10mmol/l 90 minutes after a meal: around 8mmol/l at bedtime
 · (HGB) Haemoglobin – This is a protein and transports oxygen around the body and is usually performed to assess anaemia if too low or heart disease if too high
 · Hepatitis A – This is performed to see if you have the infective hepatitis A virus (Hav) which affects the liver and to monitor your recovery process
 
 · Hepatitis B – This is done to see if the vaccine against hep B has produced an immunity or to monitor the course of the liver damage
 · Hepatitis C – Is performed to assess if you have this viral disease which inflames the liver
 · Hepatitis DDelta agent – People who have this have Hepatitis B infection already. It can make the whole situation worse for a patient if not picked up
 · INR – International Normalised Ratio – This is to test your blood clotting mechanisms for people who take anti-coagulants (blood thinning medicine) like Warfarin. The normal range is INR of 0.9 -1.1 if you are high risk the values will be different
 · Phosphorus - This is a mineral and vital for muscle and nerve functionality conditions can be affected if levels are either too high or too low
 · PTProthrombin time – This is performed to check how well your blood thinning(anti-coagulants) medicine is working
 · (RBC) Red Blood Cell count – Low levels of these cells which carry oxygen around your body can indicate Anaemia
 
 · RF - Rheumatoid Factor – This is a protein which is present in the blood when rheumatoid arthritis is suspected – some people have naturally raised levels with no rheumatoid disease present therefore these results need to be in conjunction with further tests
 · Sodium – This is part of your electrolyte levels. The ratio of these levels affect the kidneys and adrenal glands if levels are high or low it can be indicative of disease
 · TIBC - Total iron binding capacity This is a blood test which is used to detect anaemia, liver function and other blood disorders
 
 · Total Bilirubin – This is the waste product of your red blood cells and  it is what gives your faeces the brown colour. If levels are raised yellowing of the skin occurs and can be an indication of liver disease.
 
Normal levels are:-
Total bilirubin-0.3-1.0mgs/dl.
Direct bilirubin-0.1-0.3mgs/dl.
Indirect bilirubin-0.2-0.7mgs/dl

 · Total Protein – This is to measure all of  the proteins in your blood. Your doctor will be primarily looking for indications of liver or kidney disorders
 · TFT Thyroid Function TestThyroid Blood Test  -To test for levels of TSHThyroid Stimulation Hormone this indicates if the thyroid is under active or over active, this directly affects  your energy levels
 · Triglycerides – this is a form of fat. If the levels are high it puts you at an increased risk of a stroke or heart disease. To measure these levels accurately you will need to fast (not eat) for up to 12 hours before bloods are taken. These fats should not exceed 2.0 mmol/l and may be done as part of your Lipid Profile.
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