Insider Info on Lab Values

Having spent 20 years working in a hospital lab there are a few things that I can tell you as an insider about lab values:


  1. They aren’t always accurate.  Expensive equipment used to process blood samples is only as good as the person operating it and the lab technologists are only human.  Factor in to that that there is no lab test that is 100% accurate and 100% precise. If a result seems particularly abnormal or unexpected it needs to be repeated.
  2. The range for what is considered normal can be exceptionally broad, which means almost everyone is “normal” even when exhibiting symptoms of imbalance or disease.  A prime example is thyroid testing.  TSH is a hormone that stimulates the thyroid, the value will rise when the thyroid is under functioning in an attempt to increase thyroid function.  The “normal” range is 0.35 – 5.00, that doesn’t sound so bad, but if you made those numbers into whole numbers (35-500) the range looks far more broad. Many endocrinologists are saying that the cut off should be 2.50 for TSH and many patients exhibit hypothyroid symptoms when their TSH is greater than 3.00. 
  3. A lab test is only ever intended to confirm a suspected diagnosis.  That is, lab tests are not supposed to be a fishing expedition.  The doctor should have a diagnosis in mind based on all of the patient’s symptoms and use selected tests to confirm or rule out certain conditions.