Every day, in every town, physicians are asked the same questions.

Doctor what are my lab results?  Are they normal?

It seems like an easy question, and it is.  The answer, however, is not so simple.  It is up to us as Laboratorians to provide the information that physician needs to answer the question.

The physician must first consider, what is normal?

Normal, by definition, means, “the usual, average, or typical state or condition”. 

The use of “normal value” in terms of laboratory results has been changed to the more accepted, “reference range”.  Reference ranges are determined by the individual laboratory performing the test taking into account factors such as age, gender, race, etc.  It is the responsibility of every laboratory to verify the reference ranges of every analyte they report.

Reference ranges from published sources can be transferred when verified by the laboratory.  The laboratory can use their own current ranges, the manufacturer’s ranges, published reference ranges, or locally established ranges as the baseline.  The first step in the process is to establish the population to be used.  A “healthy” population can be established by using a health assessment or questionnaire.  A minimum sample population (20-25) samples is all that is required for transference of reference ranges.

In certain circumstances, published reference ranges can be transferred without verification by the performing laboratory.  This would be permitted when the population is very specific and finding sufficient samples in the population would be difficult.  Reference ranges for geriatric and pediatric patients often fall into this category.

In cases where published reference ranges are not available, the laboratory is tasked with establishing their own reference ranges.  Establishing a reference range requires a much larger population of samples to be tested.  A population of 120 +/- samples is required.  Once tested, the results are compared and the highest and lowest values (outliers) are eliminated.  The range is then established from the remaining sample values.

Second, the physician needs to consider tests that do not have a “normal value” at all.  Certain laboratory tests have decision limits instead of “normal values”.  Cholesterol is one such test.  Cholesterol is present in everyone’s blood stream.  The amount of cholesterol, however, is not as much normal vs. abnormal, as it is a predictor of cardiac risk.  The value of <= 200 mg/dL is considered the decision limit for treatment.

Other tests which have decision limits include PT/INR, Digoxin levels, drug screens, etc. Tests such as these help physicians determine if therapy is proper for the patients’ condition.

Lastly, the physician should consider hormones, which follow the body’s natural cycles.  When evaluated together, hormone values can show life cycle stages, such as ovulation, fertility, menopause, etc.  By knowing what level of hormone is typically present during these cycles, the physician can compare the patients’ results, timing of blood collection, etc. to assess the patients cycle.

So every time a physician hears that question, he can be assured that the laboratory he uses has provided him the information necessary to give his patient a simple answer. I will further explore the importance of reference range verification through an educational session at the 2015 CRI® Symposium for Clinical Laboratories next month.

About The Author

Margaret Blaetz began her career as a Medical Laboratory Technician specializing in Microbiology and obtained her Bachelor of Science Degree at Glassboro State College (Rowan University). While employed as an EMR trainer at Regional Women’s Health Management, LLC Margaret’s expertise in medical technology and project management were called into play with the planning, credentialing and opening of the Regional Women’s Laboratory. In 2012, Margaret expanded her credentials to include Certified CLIA Compliance Professional (AAPOL). Margaret serves as a CLIA regulatory resource for more than 30 Physicians Office Laboratories. Margaret’s passions include Community Theater and hound dog rescue groups; SOS Beagles NJ and Tri-State Basset Rescue. In her spare time, Margaret and her husband enjoy camping and working as Highway Hero Rescue Transporters.