Lab Results Explained

Laboratory test samples are analyzed to determine whether the results fall within normal ranges. They also may be checked for changes from previous tests. In either case your physician will go over the results with you. However, we know what it is like to make a visit to the doctor’s office; you may have to set aside a specific amount of time in your day from your regular activities, you have other things are your mind, the office can be very busy, the medical terminology can be confusing and so can the test results. So you may want to take a copy of your test results home to go over them in a more relaxed environment. The only problem is you do not have the physician there to explain things to you again. This section is designed to help you navigate your way through the test results. This information combined with other resources from the internet about what the tests are used for should provide you with enough information to get a good idea of what tests were ordered, why and what the results mean.

The reports generated by different labs can vary greatly in the type of information that is included and how it is laid out. Despite the differences in format and presentation, all laboratory reports must contain certain elements as mandated by federal legislation known as the Clinical Laboratory Improvement Amendments (CLIA).

What is normal ?

Normal test values are usually given as a range, rather than as a specific number, because normal values can vary from person to person. What is normal for one person may not be normal for another person.

Factors that affect test results

Many factors can affect test results such as: gender, age, ethnicity and medical history are typically out of our control. Other factors that can affect test results include: specific foods, drugs and how closely the patient follows pre-test instructions. This is certainly not an all-inclusive list as there are many other things that you do and things in your environment that can play a role. So, with all of this variability that exists from person to person, how do we ever get a meaningful result?

Specimen collection

Since there are many factors out of our control, it becomes very significant to control the factors we can. This underscores the significance of collecting specimens in a standardized fashion in order to perform and interpret the tests properly. It is very important to comply with your doctor’s instructions in preparing for the test(s). Your compliance with pre-test instructions will make your sample as close as possible to others in your reference group (similar age, gender etc).

Reference ranges

Some laboratory tests are precise, reliable indicators of specific health problems and provide a simple answer with no reference ranges needed. Examples of these types of tests are: blood type (A, B, AB or O) and infectious disease (either positive or negative). In many cases lab results will account for individual variability by creating reference ranges, also known as the normal range or reference interval. This range can change depending upon factors such as age, or gender. For example, when testing for testosterone, the normal range for a male is going to be much higher than that of a female. The reference range is the range within which normal values are expected to fall.

Physician Interpretation

Test results alone are typically not enough to provide a complete picture of your health. Even with standardized specimen collection and reference ranges, there are still variables that go unaccounted for. This is where your physician plays a big role.  All laboratory test results must be interpreted in the context of the overall health of the patient.  The doctor, who is familiar with a patient’s medical history and current condition, is in the best position to do this job. Some tests may just provide general information that serve as clues to possible health issues. The doctor may need to narrow down and explore the possibilities through additional tests, exams, or procedures. Eventually all of medical information gathered is pieced together to try to develop a diagnosis.

How are reference ranges established?

Reference ranges are established and validated by the lab for each test. This is accomplished by testing a large number of healthy people and observing what appears to be normal for them. In order to determine a given reference range, the population to which the reference range will apply must be defined; healthy females between 30 and 40 years old for example. The lab would obtain specimens from a large number of individuals from this population and test them for the designated test. The results would be averaged and a range (plus or minus 2 standard deviations of the average) of normal values would be established. It is common for reference ranges to vary somewhat from laboratory to laboratory. Different laboratories use different kinds of equipment and different kinds of testing methods. Therefore each laboratory must establish its own reference ranges using data from its own equipment and methods.

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