Tests and test results are used by your doctor in several ways including diagnosis of a possible disease or to monitor an existing condition. A key part of this process is to compare your results to those of healthy or ‘normal’ people. While this sounds a simple exercise, as explained in this animation
, the determination of normal values - what we call reference Intervals or reference ranges – carries a number of complications. Not the least of these is the fact that laboratories across Australia do not all use exactly the same methods or the same instrumentation. This variation in the method of testing is just one reason why reference intervals differ between laboratories and it is the major reason why we have not until now, quoted reference intervals for any of the tests on LTOAU
However, the situation is improving as the result of a project led by the professional body which hosts LTOAU
, the Australasian Association of Clinical Biochemists (AACB). AACB members, who are among the scientists and pathologists who work in pathology laboratories, have realised for some time that multiple reference intervals for the same test potentially can be confusing for doctors, patients and consumers alike. Seven years ago they embarked on a project to find ways to ensure that for certain key analytes or tests, there would only be one (harmonised) reference interval, no matter where that test was performed.
The project has taken some years because of the complexity and the size and scope of the task. It has required extensive collaboration between the professionals who are conducting the testing and those working in the companies which manufacture and produce the instruments and reagents for the actual testing process.
The tasks involved in this project included surveys of all laboratories to determine what variation existed in the reference intervals for any one test. Subsequent work involved identifying the causes of variation; in some cases a particular analytical method might be the cause in which case the supplier or manufacturer might be able to make modifications to enable it to produce results similar or identical to all other methods. In some cases, this work has led to the AACB recommending that just one method of analysis be used for a particular test and all laboratories adopting it.
For some analytes there are significant differences in values or intervals for males and females – in other words it is not possible to use a single interval for all people for that test and accordingly there is a specific interval for men and another for women. One of the most important parts of the Harmonisation project has been to recognise that test values for some analytes change markedly in neonates or young children as they grow and so a considerable amount of work has gone into the determination of age-related reference intervals for paediatric patients.
Australia has led the world in this important area of pathology testing and is the first country to adopt harmonised reference intervals that have been determined on a scientific basis. These intervals for 18 adult tests and for nine paediatric tests are now available on Lab Tests OnlineAU
All laboratories have agreed to adopt these ranges but it may take a period of time before they appear on your pathology report. While those tests with harmonised reference intervals are among those most commonly requested, they are only a small number of all the possible tests that can be requested. The Harmonisation project has tackled what might be called the “low hanging fruit”! But work continues to harmonise the reference intervals for more complex tests.
Reference intervals (also known as reference ranges) are a way of comparing your test results with those considered normal for the general population.