Laboratory Tests Based on Reference or Average Ranges May Fail to Adequately Diagnose Existing or Potential Diseases.

Laboratory Tests Based on Reference or Average Ranges May Fail to Adequately Diagnose Existing or Potential Diseases.
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What Is a Reference Range?

In general practice, particularly with short appointment times and many patients, typically doctors simply scan down the lab tests abnormal column looking for an “H” meaning High or “L,” Low. If nothing is there, they assume there are no problems. This can lead to missed early diagnosis of potential problems. There is a faulty assumption that laboratory tests with values in the “reference range” ipso facto prove a healthy state. The problem in this logical error is that reference ranges are derived from average values in the whole population. This can lead to overly broad ranges that may fail to detect developing problems. To take an extreme example to illustrate the problem, it is as if a laboratory tested a population of severely overweight individuals, between 250 to 350 pounds, and concluded the average reference range was between 275 and 375. Another example relating to the thyroid function test was discussed in a Lancet article in 2002 with the title “Whose normal thyroid function is better—yours or mine?” Researchers maintained the reference ranges for thyroid level was so broad it did not show what the optimal level was for an individual [1]. In fact, more research suggests that values at the upper level may predict coming thyroid disease and even heart disease.

Mistaken Reference Ranges

In the 1960s statistical analyses of lab tests for cholesterol established a reference range for cholesterol that went up to the 300 mg/Dl. Of course, it was also considered “normal” for men to have heart attacks at much younger ages than currently. The more medicine learned about cholesterol and cardiac problems, the more the level dropped to where it is now, under 200 mg/Dl.

Another marker for coronary disease is homocysteine level. At one time levels of homocysteine up to 15 mcml/L were considered “normal.” Now levels above 10 mcml/L are considered a risk factor for heart attack and stroke, while other authorities claim below 7 micromoles per liter are optimal..

In aging males, reference ranges in laboratory tests may be really out of date. These men often have excess insulin and estrogen with deficiencies of testosterone and dehydroepiandrosterone (DHEA). The normal reference ranges for these hormones are so broad that many men could be at risk for a multitude of diseases while their doctors tell them the levels are “normal.” Instead, patients should be talking with their regular doctors or endocrinologists about what the “optimal” ranges are in their case.

Examples

Reference values may differ a bit from one laboratory to another. Here are some standard and optimal ranges as suggested by one source [2]:

  • Estradiol: Normal range (male), 3 to70 pg/mL; Optimal range, 10 to 30 pg/mL.
  • Fasting glucose: Normal range, 65 to 109 mg/DL; Optimal range, 70 to 100 mg/DL.
  • LDL Cholesterol: Normal range, less than 129; Optimal range, less than 100.
  • Thyroid Stimulating Hormone (TSH): Normal range, 0.35 to 5.5 mcIU/ml; Optimal range, under 2.1 mcIU/ml.
  • Triglycerides: Normal range, 0 to 199 mg/dL; Optimal range, 40 to 100 mg/dL.

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References

[1]. Dayan, CM, et. al., “Whose normal thyroid function is better—yours or mine?” Lancet 2002 Aug 3;360(9330):353.

[2]. Disease Prevention and Treatment, 4th ed. (Hollywood, FL: Life Extension Foundation, 2003), pp. 1058-1067.