For many blood tests there are specific paediatric reference intervals (ranges).
In specialist settings we can see reference intervals for premature, term, neonates and various age bands up to 16 or 18 years old. Even, sometimes, separate consideration of young adults between 18 and maybe mid-twenties.
Sometimes the paediatric reference intervals are only slightly different from adult reference intervals - but some are substantially different.
If you are looking at results of any tests for younger people, check that the reference intervals you have are the proper reference intervals for their age.
It is not unusual for labs not to have produced paediatric reference intervals for all the tests they perform. It is a major overhead to do so. Some tests might only rarely be performed on younger patients which means that it might have been impossible to derive using standard approaches. In such cases, the lab might look to the literature to see what is known, or use manufacturer reference intervals without further revalidation within the lab.
It is all too common for the doctors involved to miss this issue. And I'm not convinced that labs always put the right reference intervals on printouts of results!
This paper discusses some of the issues and actually specifically discusses thyrotropin (TSH) and Free T4 tests.
Current State of Pediatric Reference Intervals and the Importance of Correctly Describing the Biochemistry of Child Development A Review
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10155856/
If considering specifically thyroid-related blood tests, this article from Thyroid Patients Canada is well worth reading:
Pediatric and teenage TSH, FT4, and FT3 levels
https://thyroidpatients.ca/2022/07/27/pediatric-teenage-tsh-ft4-ft3/
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[i][b]helvella - Paediatric Reference Intervals[/b]
Discussion of the importance of using paediatric reference intervals for interpreting laboratory test results.
Last updated 10/02/2025[/i]
Link to blog:
https://helvella.blogspot.com/p/helvella-paediatric-reference-intervals.html
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