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Dynamic Chiropractic Canada – March 1, 2010, Vol. 03, Issue 02
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The Reference Range Is Not Normal

By Daniel Hough, DC

Laboratory reference ranges are not synonymous with normal. Most physicians have the misconception that the reference range provided by the testing laboratory is the same as the normal range.

Many chiropractors don't even order laboratory work-ups on their patients, despite the fact that in most states, chiropractors are licensed as primary care physicians. How can you be a primary care physician and not use laboratory analysis as one of your diagnostic tools?

Laboratory analysis of blood, saliva and urine are safe, inexpensive and reveal much about your patients. The biggest risk involved with lab work is that the patient's medical doctor will misinterpret it, make the wrong diagnosis and prescribe a dangerous, expensive pharmaceutical to treat the wrong problem. As a chiropractor, even if you don't order tests, you can make a huge difference in your patient's health by taking a look at the diagnostic work their medical doctor has ordered and giving your professional opinion.

The two most important things to remember when interpreting bodily fluid diagnostic studies are: 1) A patient can still be sick and be within the reference range; and 2) The lab results should correlate with the patient's signs and symptoms. Reference ranges are derived by taking a sample of a number of lab results from "normal patients" and then applying a bell curve to those results. The numbers are then sometimes modified by input from experts in the field to arrive at the reference range provided with the test results.

The following two examples serve to illustrate my point that the reference range is not normal and that it does not necessarily mean the patient is "OK" if the lab results indicate levels (of whatever is being tested) within that range:

Thyroid Function Tests

Thyroid function tests, specifically TSH (thyroid-stimulating hormone) reference ranges, vary depending on which lab is used. For example, Z.R.T. Lab uses the reference range for TSH of 0.3 to 3.0; the lab in Bozeman, Mont., that I use has a reference range for TSH of 0.5 to 3.4; and a Billings, Mont., lab reports a reference range of 0.5 to 4.5. If a physician believes the reference range defines normal, then a patient living in Billings with a TSH of 3.8 is considered normal, but if they move 140 miles west to Bozeman, then they are hypothyroid.

Of course, that is nonsense. It is just as ridiculous to think that with two patients both suffering from fatigue, cold intolerance, depression and constipation with TSH lab values of 2.95 and 3.05, respectively, that one is normal and the other is hypothyroid.

In 2002, the American Academy of Clinical Endocrinologist decided that the appropriate range for TSH was 0.3 to 3.0. Unmedicated or undermedicated hypothyroidism predisposes patients to osteoporosis, heart disease and depression. I am suspect of a TSH levels over 2.0 if the patient exhibits signs and symptoms of low thyroid. In those cases, I order either a T3 Free or a T4 Free and consider those patients to be in fact hypothyroid unless those numbers are in the mid reference range for those tests.

I believe T3 Free or T4 Free to be more accurate tests for assessing hypothyroidism, as TSH misses central hypothyroidism and misses those patients who do not properly convert T4 into T3.1 Most physicians order a TSH to assess thyroid function. TSH is a test that has more false negatives than real negatives and is of very little value, in my opinion.

Uric Acid Tests

Uric acid tests, which are ordered to diagnose gouty arthritis, have reference ranges well above the level that gouty arthritis can be present. Medical Laboratory in Bozeman reports an upper reference range of 8.2 mg /dl for males. A patient can be symptomatic with gout at any level above 6.0.2 Many physicians miss cases of gouty arthritis because they believe a uric acid level under 8.2 rules out gout and they also have the misconception that gout only occurs in the great toe. Gouty arthritis can manifest in any joint of the body, as well as in soft tissue.3

Use Lab Testing to Play a Greater Role in Your Patients' Health

At least once a month, I see lab work on one of my patients who was not properly evaluated; mostly it is hypothyroid patients who have not been diagnosed or have been diagnosed but are being undermedicated (I know that sounds strange, coming from a DC) because their physician is titrating their medication dose based on TSH, (which is a bad idea),4 or they are being prescribed a synthetic hormone replacement that only contains thyroxine. A preparation that also contains the active form of thyroid hormone, triiodothyronine, works much better. A referral to a naturopathic physician is usually necessary to get your patients properly medicated.

Moreover, at least a half a dozen times a year I see a case of gouty arthritis in a joint other than the great toe; usually the patient's uric acid levels are between 6.0 and 8.5. In short, proper interpretation of your patient's laboratory results can make a huge difference. It also has the added benefit of increasing your participation in your patients' care, which can reinforce your role (in their eyes) as an authority on their overall health.

References

  1. Hough D. "What Every Chiropractor (and MD) Should Know About the Thyroid."  Dynamic Chiropractic, April 7, 2003.
  2. Yochum T, Rowe L. Essentials of Skeletal Radiology. Williams and Wilkins, 1987:659-665.
  3. Hough D. "Gouty Arthritis: The Missed Diagnosis."  Dynamic Chiropractic, Sept. 18, 2000.
  4. Lowe J. The Metabolic Treatment of Fibromyalgia (not just about fibromyalgia). McDowell Publishing Co., Boulder, CO:992-996.

Dr. Daniel Hough is a 1991 graduate of Western States Chiropractic College. A former member of the Montana Chiropractic Association Ethics Committee, he practices in Bozeman, Mont.

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