Blood counts Reference Ranges Analyzer
Published: 19 May 2024
For simplicity, we use the term reference range in this article.
The term 'normal range' is not used very much today because it is considered to be misleading. Tests results-all medical data-can only be understood once all the pieces are together. Most people know that the 'average' heart rate is about 70 beats per minute. Without the proper context, any observation or test result is meaningless. Therefore, today 'reference range' or 'reference values' are considered the more appropriate terms, for reasons explained on the next page. The term reference values is increasing in use and is often used interchangeably with reference range. How do you know what a 'normal' heart rate is? We know this on the basis of taking the pulse rate of millions of people over time. If a patient's results are outside the range for that test, it does not automatically mean that the result is abnormal. You can take your resting heart rate right now by putting your fingers on your pulse and counting for a minute. To understand what is normal for you, your doctor must know what is normal for most other people of your age and what you were doing at the time-or just before-the test or observation was conducted. Take one of the simplest medical indicators of all-your heart rate. Your heart rate, like any medical observation, must be considered in context. You probably also know that if you are a regular runner or are otherwise in good physical condition, your pulse rate could be considerably lower-so a pulse rate of 55 could also be 'normal.' Say you walk up a hill-your heart rate is now 120 beats a minute. The interpretation of any clinical laboratory test must consider this important concept when comparing the patient results to the test 'reference range'.That would be high for a resting heart rate but 'normal' for the rate during this kind of activity.
A large number of individuals from a group who are thought to represent a 'normal' population, will be tested for a particular laboratory test. Indeed for tests such as cholesterol the idea of a normal range has been replaced to a large extent by use of target values, achieved either by lifestyle changes or active treatment.
Whether or not your test result is within the laboratory reference range, the result must be considered within the context of your personal circumstances, and with the benefit of your doctor's knowledge of your past medical history, current medication and the results of any other investigations.This is why the term 'reference range' is preferred over 'normal range'.
When you examine test results from different populations, you quickly discover that what is 'normal' for one group is not necessarily normal for another group. In this way, ranges quoted by labs will represent the values found in 95% of individuals in the chosen 'reference' group. The first step in determining a reference range is to define the population to which the range will apply. The reference range is then derived mathematically by taking the average value for the group and allowing for natural variation around that value (plus or minus 2 standard deviations from the average). In other words, even in a 'normal' population, a test result will lie outside the reference range in 5% of cases (1 in 20).
The term 'normal range' is not used very much today because it is considered to be misleading. Tests results-all medical data-can only be understood once all the pieces are together. Most people know that the 'average' heart rate is about 70 beats per minute. Without the proper context, any observation or test result is meaningless. Therefore, today 'reference range' or 'reference values' are considered the more appropriate terms, for reasons explained on the next page. The term reference values is increasing in use and is often used interchangeably with reference range. How do you know what a 'normal' heart rate is? We know this on the basis of taking the pulse rate of millions of people over time. If a patient's results are outside the range for that test, it does not automatically mean that the result is abnormal. You can take your resting heart rate right now by putting your fingers on your pulse and counting for a minute. To understand what is normal for you, your doctor must know what is normal for most other people of your age and what you were doing at the time-or just before-the test or observation was conducted. Take one of the simplest medical indicators of all-your heart rate. Your heart rate, like any medical observation, must be considered in context. You probably also know that if you are a regular runner or are otherwise in good physical condition, your pulse rate could be considerably lower-so a pulse rate of 55 could also be 'normal.' Say you walk up a hill-your heart rate is now 120 beats a minute. The interpretation of any clinical laboratory test must consider this important concept when comparing the patient results to the test 'reference range'.That would be high for a resting heart rate but 'normal' for the rate during this kind of activity.
A large number of individuals from a group who are thought to represent a 'normal' population, will be tested for a particular laboratory test. Indeed for tests such as cholesterol the idea of a normal range has been replaced to a large extent by use of target values, achieved either by lifestyle changes or active treatment.
Whether or not your test result is within the laboratory reference range, the result must be considered within the context of your personal circumstances, and with the benefit of your doctor's knowledge of your past medical history, current medication and the results of any other investigations.This is why the term 'reference range' is preferred over 'normal range'.
When you examine test results from different populations, you quickly discover that what is 'normal' for one group is not necessarily normal for another group. In this way, ranges quoted by labs will represent the values found in 95% of individuals in the chosen 'reference' group. The first step in determining a reference range is to define the population to which the range will apply. The reference range is then derived mathematically by taking the average value for the group and allowing for natural variation around that value (plus or minus 2 standard deviations from the average). In other words, even in a 'normal' population, a test result will lie outside the reference range in 5% of cases (1 in 20).