Prevention Tip of the Month

 

Understanding "Routine" Blood Work

 

 

Did you ever wonder how your doctor decides what lab work to draw when you go for an appointment?  It will depend, at least in part, on the reason for your visit.  If you are a new patient, the doctor will perform a history and conduct a physical exam.  That gives the doctor quite a bit of information, but typically, your doc will want to draw “routine” lab work. If you are an established patient and have a specific complaint or condition, there may be a reason to perform lab work that is not necessarily considered “routine”.  If Medicare is your primary insurance, the doctor must be able to justify the lab work that is ordered so that it coincides with the diagnoses for that visit. 

 

 

 

Three of the most commonly performed lab tests, especially on new patients, are the Complete Blood Count (CBC), the Comprehensive Metabolic Profile (CMP) and the Basic Metabolic Profile (BMP).  The Complete Blood Count tells the doctor about the numbers of red and white blood cells, their size, shape and distribution according to cell type.  There are several different types of white blood cells.  This is the test upon which a diagnosis of anemia, leukemia and certain other types of blood disorders is made.  At times, a follow up test will be necessary if the diagnosis is not clear from a CBC.

 

 

 

The Comprehensive Metabolic Profile, also known as multiple chemistry profile, was standardized several years ago, and usually includes 14 different tests that give us a lot of information about the normal function of your body.  It includes what are commonly known as electrolytes (substances that keep your body’s electrical system functioning), proteins and enzymes required for normal liver, kidney, bone, muscle, and heart and lung function, glucose (blood sugar), and measurements of kidney filtration and liver processing capability.  There is some variation among labs in terms of tests included and what are considered normal values, but generally, we will get:

            Glucose – blood sugar

            Calcium – bone, muscle, kidney function

            Albumin – liver protein

            Total Protein – albumin + all other proteins

            Sodium - electrolyte

            Potassium - electrolyte

            CO 2 (carbon dioxide or bicarbonate) - electrolyte

            Chloride - electrolyte

            BUN – kidney function

            Creatinine – kidney function

            ALP (alkaline phosphatase) – liver function

            ALT (alanine transaminase) – liver function

            AST (aspartate aminotransferase) – liver function

            Bilirubin – liver function

 

Some labs will include additional tests such as Total Cholesterol, Uric Acid, Phosphorus and GGT (gamma-glutamyl transpeptidase).

 

 

A Basic Metabolic Profile is an abbreviated version of the Comprehensive Panel and will usually include 6 or 7 of the above tests.  Typically those will be glucose, sodium, chloride, CO 2, potassium, BUN/Creatinine.  It is simply a matter of clinical judgment on the doctor’s part when to order the comprehensive versus the basic panel.

 

 

If all the tests come back normal, it doesn’t necessarily mean that you are completely healthy but it is a very good indication that your baseline body functions are working normally.  Some conditions don’t show up in “routine” lab work.  Your doctor looks for both high and low values when reviewing the tests because both are important.  Your doctor can also make a judgment about whether something that is just slightly out of kilter has clinical significance or not.   

 

 

Even if you don’t understand how to pronounce some of the words or the specific purpose of each test, it’s always a good idea to ask your doctor to go over the lab reports with you and spell out what areas of body function were tested and whether he or she has any concerns based on lab results.  Also, if you know there is something that your doctor should be checking regularly, but is not included in “routine” blood work, a gentle reminder never hurts. 

 

 

As mentioned above, cholesterol tests are not always included in the comprehensive profile, and may have to be ordered separately.  The same is true of thyroid tests and Hemoglobin A1C – the test for long term blood sugar control.

 

 

So, it’s prudent on your part if the doctor says, “All your blood work was normal.” to get a little more of an explanation about what that means.  I think it’s also wise to ask for and keep a record of your lab work for future reference.  A few people these days see the same doctor year after year but it’s becoming less common and you can’t always be sure that your records will be transferred in a timely way.  As the old saying goes – an ounce of prevention is worth a pound of cure.