Calculated Chemistry Parameters - do they need to be harmonised?

In clinical chemistry, harmonisation of the testing process is a global initiative with the purpose of improving patient safety, allowing better integration of research data and enabling the use of national electronic heath records. In Australia, as in other countries, the initial focus has been on the harmonisation of the more commonly measured analytes. There are also a number of calculated parameters, derived from these measured analytes, which could also be considered for harmonisation. Calculated parameters that are reported by laboratories and used for clinical decision-making should undergo the same robust process of harmonisation as is the case for the measured analytes. Aspects that should be considered for harmonisation are: terminology, the formulae used and where possible the use of common reference intervals. To investigate pathways towards the harmonisation of calculated parameters, three commonly reported parameters are considered. Calculated osmolality, the anion gap and albumin-adjusted calcium are all derived from common analytes which have individually been considered for harmonisation. They present different methodological, measurement uncertainty and terminological hurdles to harmonisation and are likely to require different pathways and solutions.