WORLD HOSPITAL DIRECTORY
Extended Reading.....
Medical Tests: What Does a Normal Range Mean?

Medical Tests: What Does a Normal Range Mean?We have a marvelous array of medical tests available to us. Many of them-typically blood-tests-even come with results expressed in numbers signifying the exact quantity of something that was measured. On laboratory reports these measured quantities are often accompanied by a "normal range" for what the laboratory apparently thinks the value should have been, showing a lower number and a higher number. So if you had a laboratory test, what does it mean when your measurement falls inside or outside this range?

It all depends on the particulars. First of all, it matters what is being measured and why it was measured in the first place. In theory, a laboratory test is ordered when the doctor poses a question for which the laboratory test is supposed to provide an answer. (If there was no question, how could the lab-test be an answer?) For example, suppose a doctor is wondering if your hand tremors are due to too much thyroid-hormone in your bloodstream. So the doctor's question is: Does this person have too much thyroid-hormone in the bloodstream? A test measuring the thyroid-hormone would provide a clean answer if it was either too high (yes) or within the normal range (no). Because thyroid-hormone levels that are too low do not produce tremors, a measurement that was too low would be irrelevant to the question posed. It might still warrant consideration in its own right as an "incidental finding," but is no different than a within-range outcome in answering the original question.

How about the same blood-test, but with a different question? Suppose the doctor is trying to figure out why you gained weight. The doctor knows that some people gain weight when their thyroid glands produce too little thyroid-hormone. So the doctor's question is: Does this person have too little thyroid-hormone in the bloodstream? This time, measuring the thyroid-hormone would provide a clean answer to the question if it was lower than the normal range (yes) or within the normal range (no). Because elevated thyroid-hormone levels do not usually cause weight-gain, a number higher than the normal range would produce an answer to the original question no different than one that was within-range. (But even if this outcome was unexpected, it might still be followed up.)

For some blood-tests the only meaningful result is in one direction. For example, a blood urea nitrogen (BUN) measurement assesses kidney function. If the BUN measurement is too high, it could signify that the kidney is impaired. But what does it mean if your BUN measurement is lower than the normal range? It means absolutely nothing. It's a non-event. So then it's curious that a normal range for BUN even includes a lower number. How did it get there?

These examples lead up to the question of how the normal ranges are created in the first place. They are produced by statistics generated by measurements obtained in healthy volunteers. In the case of the BUN measurement, for example, this substance might get measured in the blood of, say, 100 people without kidney disease. An average number would be calculated by adding the numbers produced by all 100 people, and then dividing by 100. This average would be the center of the normal range.

But the upper and lower numbers are produced by another method looking at how widely spread apart the BUN measurements are in these 100 people. After all, it would be highly unlikely that all 100 people would produce the exact same number-value. So how far from the average is still okay? The 100 measurements are plugged into a mathematical formula to compute a "standard deviation," a widely-used statistic related to how widely the numbers are spread apart. Numbers that are farther apart produce a larger standard deviation, while numbers that are closer together produce a smaller standard deviation.

The next step is to decide how many standard deviations above and below average should be accepted as normal. A typical choice for a blood-test is two standard deviations in either direction. It is known that measurements falling within the range of two standard deviations above and below the average will include, on average, 95% of the healthy people. It will also exclude or label as apparently abnormal the other 5% of healthy volunteers. So if the "normal range" is generated in this fashion, one thing we already know is that it will be wrong 5% of the time.

Another outcome of this statistical system is that if your doctor measures twenty different things in your bloodstream, then, on average, one of them will be outside its normal range-even if you are totally healthy!

Moreover, the statistical method automatically generates a lower and an upper value. This is done without consideration of whether or not it means anything to be too high or too low. The normal range merely expresses typical values obtained in healthy volunteers. It is up to your doctor to determine whether or not a result outside the normal range is clinically meaningful. The "normal range" is not a judgment; it is merely a statistical statement. You want the judgment to come from a trained clinician.

Your doctor has special words that are useful in navigating this intersection between statistics and clinical meaning. One favorite word is "unremarkable." You might not like the idea of being described as unremarkable. But this is a handy term that your doctor uses to lump together your laboratory results that fell within their normal ranges with those that fell outside their normal ranges but were still considered benign. So in this case, "unremarkable" is a good thing to be.

(C) 2005 by Gary Cordingley

Gary Cordingley, MD, PhD, is a clinical neurologist, teacher and researcher who works in Athens, Ohio. For more health-related articles see his website at: http://www.cordingleyneurology.com






 
1.
Why Our Healthcare System Isnt Healthy
Why Our Healthcare System Isnt HealthyMost people are well aware that an estimated 45 million Americans currently do not have healthcare, but is the crisis simply the lack
More >>
2.
Stopping Hospital Infections
Stopping Hospital InfectionsEach year hospitals end up killing twice as many people than automobiles, some 90,000 deaths in the United States. It is not from malpractice, i
More >>
3.
Protect Yourself Against the Flu Vaccine!
Protect Yourself Against the Flu Vaccine!<br />
The vaccine industry insists that their vaccines against the flu serve as the key to a healthy winter. Although there has
More >>
4.
Chinese Medicine
Chinese MedicineChinese Medicine, over 2000 years old, is an ancient form of medicine. Consisting of acupuncture, moxibustion (moxibustion - using material made up of
More >>
5.
Medical Billing Specialist
Medical Billing SpecialistAs Pres. Bush was touring the Midwest, shortly before he was re-elected as President, and even after, he spoke of medical reform centering on
More >>
6.
Nasonex And You: Breathe Easy, Not Sneezy
Nasonex And You: Breathe EasyWhile everybody else is wandering around enjoying the spring weather, are you hiding out in your hermetically-sealed house? Do you dread the star
More >>
7.
Chronic Headaches and Pain Often Can Be Eliminated By A Special Dentist
Chronic Headaches Often Can Be Eliminated By A Special DentistDENVER ? Sometimes as Freud once said a good cigar is just a smoke. A headache, on the other hand, occas
More >>
8.
Physicians, Chiropractors and Physical Therapist Agree on a New Treatment for Low Back Pain
New Treatment for Low Back Pain<br />
One of the most prevalent and difficult health conditions to treat in the physical medicine is low back pain. The difficulty in tre
More >>
9.
Web Therapy: Enhancing Patient Communication with Web Access
Web Therapy: Enhancing Patient Communication with Web AccessAccording to Jennifer Lyons' chart, she's just a bad slip and fall who's lucky enough to be on her way to a full
More >>
10.
Increasing Patient Care and Reducing Liability in Seven Simple Steps
Increasing Patient Care and Reducing Liability in Seven Simple StepsWhen an unconscious patient arrives in the ED, every hospital agrees that timely next of kin notificat
More >>
11.
Cetyl Myristoleate Seperating Fact From Fiction
Cetyl Myristoleate Seperating Fact From FictionI am a strong believer in Cetyl Myristoleate for the treatment of arthritis. For the last three years I have been res
More >>
12.
Medical Tests: What Does a Normal Range Mean?
Medical Tests: What Does a Normal Range Mean?We have a marvelous array of medical tests available to us. Many of them-typically blood-tests-even come with results expressed
More >>
13.
CT and MRI Scans in Neurological Practice
CT and MRI Scans in Neurological Practice

Before computed tomographic (CT) scans became available in the 1970s, there was no good method for imaging the brain. The a
More >>
14.
Alcohol Rehabilitation Centers - Take An Informed Decision
Alcohol Rehabilitation Centers - Take An Informed DecisionAlcohol rehabilitation centers in the United States offer a wide range of treatment programmes for your recovery f
More >>
15.
Contact Lenses and Eye Glasses
Contact Lenses and Eye GlassesHow is Your Vision?
Notice friends getting contact lenses and pulling out eye glasses?

"What do you recommend?"

More >>
16.
Death by Fluoride
Death by FluorideA wee bit of fluoride makes teeth and dentists happy, we're told. Dr. Happy Tooth's smiley face turns into a frown when his favorite decay buster is busted
More >>
17.
10 Steps To Detoxification
10 Steps To DetoxificationTechnology. We live in a grand time of technological development. Computers, the Internet, cell phones, digital cameras and DVDs. But the human body h
More >>
18.
New Surgical Treatment Options for Hernias
New Surgical Treatment Options for HerniasHernia repair is one of the most commonly performed surgical procedures worldwide. In fact, there are over 600,000 hernia repa
More >>
19.
Arthritis Pain Relief : FAQ
Arthritis Pain Relief : FAQA great place to begin taking charge of you arthritis pain relief and prevention planning is by making an appointment with your healthc
More >>
20.
A Surgical Robot Fixes Heart in Brazil
a Surgical Robot Fixes Heart in BrazilBrazilian surgeons used a multi-armed robot to repair a hole in a woman's heart in the first operation of its kind in Latin Americ
More >>
21.
Root Canal Therapy:FAQ
Root Canal Therapy:FAQOverview

A diseased or injured nerve use to mean that you were likely to lose a tooth. This is no longer the case thanks to root
More >>
22.
ADHD - Are there Treatment Options?
ADHD - Are there Treatment Options?As an ADD coach I am often asked about the treatment options available for Attention Deficit Disorder. Generally when someone says "ADD" the f
More >>
23.
7 Tips to Keep Your Fluid Down on Dialysis
7 Tips to Keep Your Fluid Down on DialysisAs any dialysis patient will tell you, keeping your fluid gain between dialysis sessions in check is not only important to your lon
More >>
24.
Testosterone Therapy in XXI Century
Testosterone Therapy in XXI CenturyNowadays many people are familiar with the appellation of "low testosterone level". What does it mean? It mean that male body p
More >>
25.
Stem Cell Research
Stem Cell ResearchHow To Buy Your Way Out Of An Early Death From An Incurable Disease.

How?... With private stem cell research, of course!?Stem cell research
More >>
1.
Maharashtra woos medical tourists
Maharashtra woos medical touristsMany people from the developed world come to India for the rejuvenation promised by yoga and ayurvedic massage, but few consider it a de
More >>
2.
Medical tourism: Need surgery, will travel
Maharashtra woos medical touristsA worldwide market

What's called medical tourism – patients going to a different country for either urgent or ele
More >>
3.
Medical Tourism is Becoming a Huge Industry in India
Diatance LearningMany types of medical treatment in India cost a fraction of what they do in the United States and other Western nations, and citizens from these c
More >>
4.
Medical tourism set to take off in a big way
Medical tourism set to take off in a big wayWith world class healthcare professionals, nursing care and treatment cost almost one-sixth of that in the developed
More >>
5.
India eyeing share in medical tourism pie
India eyeing share in medical tourism pie A NICE blend of top-class medical expertise at attractive prices is helping a growing number of Indian corporate hospitals lure forei
More >>
6.
Are we ready for medical tourism?
Are we ready for medical tourism? The private healthcare industry is quietly facilitating a revolution to enable India to emerge as a health destination. Yet there are the
More >>
7.
Is medical tourism worth the risk?
Is medical tourism worth the risk?Thousands of Britons are heading abroad for cut-price treatment. We investigate the health tourism boom and asks if the benefits o
More >>
8.
Package holiday surgery to beat NHS queue
Package holiday surgery to beat NHS queueA holiday firm is offering 'sun and surgery' package deals to India for patients tired of waiting for the NHS.

Th
More >>
9.
Choosing the right weight loss surgery abroad
Choosing the right weight loss surgery abroadThe reluctance of public healthcare systems and health insurers to fund weight loss surgery means that more and more people are
More >>
10.
The forgotten medical tourism destination
The forgotten medical tourism destinationAn article by medical tourism specialist, Ian Youngman, on one of the world’s leading destinations for medical travelers which s
More >>
11.
Why medical tourism needs facilitators
Why medical tourism needs facilitatorsFollowing our recent article on "How can patients judge quality in medical tourism?", Caroline Ratner spoke to Mike Silford, who run
More >>
12.
How can patients judge quality in medical tourism?
How can patients judge quality in medical tourism?There's much discussion and hype around the medical tourism world about “quality”. Every hospital, clinic, h
More >>
13.
The importance of social media and the web in medical tourism
The importance of social media and the web in medical tourismMore than most other industries, medical tourism agencies and international patient departments rely heavily on t
More >>
14.
Medical Tourism Destinations: Places That Top The Charts
Medical Tourism Destinations: Places That Top The ChartsMedical tourism is a popular trend among people in the US nowadays. Many Americans are moving abroad to get tr
More >>
15.
Plastic & Cosmetic Surgery Option In Malaysia
Plastic & Cosmetic Surgery Option In MalaysiaMedical Tourism Malaysia is growing at an exponential growth factor. Its enjoying medical tourist from UK, Australia, New Zealand
More >>
16.
Samitivej Medical Tourism, A Lucrative Business
Samitivej Medical Tourism, A Lucrative BusinessSamitivej Wins 2 Prestigious HMA Awards 2008 Path to Being the Largest Medical Tourism

Samitivej, a leading pri
More >>
17.
Jordan pushes medical tourism industry
Jordan pushes medical tourism industryAfter establishing itself as a popular destination for medical care among Arabs in the Middle East, Jordan is now looking to attract more
More >>
18.
Some Frequently Asked Questions about Medical Tourism
Some Frequently Asked Questions about Medical TourismWhat is the quality of care that I can expect? Most of the healthcare centers abroad such as hospitals clinics and diagnostic
More >>
19.
Infertility Treatment in India
Infertility Treatment in IndiaInfertility is the inability to conceive a child by natural means. When a couple finds it difficult to conceive naturally, medication and spe
More >>
20.
Medical Tourism Thailand
Medical Tourism ThailandThailand has been a popular holiday destination of the East which is now a popular medical tourism destination as well. The Thai medical service is on
More >>
21.
Medical Tourism India
Medical Tourism IndiaA medical tourist in India can get the best of both worlds- excellent medical service from experts in the field of medicine and a splendid experience of a
More >>
22.
Digitizing Medical Documents
Digitizing Medical DocumentsIt is a common fact that hospitals and doctors need a patient’s detailed medical history before treating them. But when you have tr
More >>
23.
Roux-en-gastric bypass in India: An Overview
Roux-en-gastric bypass in India: An OverviewRoux-en-gastric bypass in India is very economical and affordable. Low cost but quality treatment attracts many patients of a
More >>
24.
Need a dentist? Come to Croatia
Need a dentist? Come to Croatia







Croatia has decided to take an unconventional approach to tourism - with dentists taking
More >>
25.
India offers hope for those too sick to wait
India offers hope for those too sick to waitEmerging into the teeming chaos of people, cows and honking vehicles outside Bangalore airport, retired teacher John Stauffer wonde
More >>