Labs, The Sequel

Lab data is a simple resource to identify areas of possible impairment.  We have already seen how the hemogram (CBC) can locate blood disorders like anemia, leukemia and thrombocytopenia.  Another routine but very important lab test is the blood chemistry panel, or comprehensive metabolic panel (CMP).  The most recognized test is the glucose level, a hallmark for identifying new onset of diabetes, and also for monitoring control for known diabetes.  The glucose level indicates the amount of glucose in the blood stream.  Fasting labs are ordered to isolate what is in your blood stream and are unimpacted by the donut you just ate.  A common specialized lab test for diabetes is the A1c, which measures a 2-3 month average of glucose control. 

Blood urea nitrogen (BUN) and creatinine (CR) gauge the function of the kidneys.  Of the two, CR is more important, and when elevated, indicates renal dysfunction.  Chronic mild CR elevation is referred to as renal insufficiency.  More significant is chronic CR elevation, known as renal failure.  The glomerular filtration rate (eGFR) shows the efficacy of the kidney filtration system.  As the CR rises, the eGFR will decrease.  Treatment for either is to avoid dehydration (which can temporarily damage the kidney) and avoid NSAIDS and other nephrotoxic (nephro=kidney, toxic=you know) medications.  As the kidneys deteriorate, the buildup of toxins in the blood stream requires outside help, in the form of dialysis.

Electrolytes, also known as minerals, can reveal metabolic imbalances.  One of the more serious imbalances includes elevated potassium, because it affects impulse conduction in the heart and can cause palpitations.  Sodium (Na) and chloride (Cl) play major roles in water regulation in the body on a cellular level.  Decreased Na and Cl may be caused by dehydration, resulting in confusion and even seizures if left untreated.  Liver dysfunction can be readily identified by elevation of two liver enzymes with big, long names, simply abbreviated AST and ALT.  The elevations are caused by inflammation or damage to the liver cells.  Common causes of the damage are alcohol intake, hepatitis and fatty liver disease.  Additional liver markers, bilirubin and alkaline phosphatase, can also reveal liver problems.

Calcium is necessary for the function of nerves, muscles and heart.  Elevations may weaken bones and create renal stones.  Low levels of calcium can cause confusion, depression, and stiff, aching muscles.  Both hypercalcemia (hyper=increased) and hypocalcemia (hypo=decreased) can be caused by parathyroid gland dysfunction (don’t ask).

The takeaway from the above is this: the CMP can identify imbalances in the body’s blood chemistries and therefore, the body’s metabolism.  Any lab value that is not normal would then be followed up by treatment (ie increased electrolyte ingestion), follow up labs to monitor stability (ie glucose elevation) and/or further testing (ie ultrasound for elevated AST /ALT).