The current issue of The Clinical Biochemist Reviews focuses on the continuing laboratory harmonisation activities being undertaken by the Australasian Association of Clinical Biochemists (AACB) and the Royal College of Pathologists of Australasia (RCPA). It includes an update on common reference intervals (RI) and the feasibility of harmonising calculated biochemistry parameters routinely used in our laboratories.
In 2015 the AACB held both a harmonisation workshop and a webinar to discuss and reach a consensus on using common RIs for six further chemistry analytes in adults. These were: alanine transaminase (no pyridoxal 5-phosphate; ALT), aspartate transaminase (no pyridoxal 5-phosphate; AST), gamma glutamyl transferase (GGT), creatine kinase (CK), lipase, and total bilirubin.1 The RIs add to the 12 others that have already been agreed upon and endorsed for use in Australasia.2 As discussed in the paper by Koerbin et al.1, a future goal may be for Australian laboratories to use International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) methods for transaminase analysis. Currently however the majority of Australasian laboratories continue to use non-pyridoxal 5-phosphate assays for ALT and AST; therefore the AACB decided that a harmonised RI with non-pyridoxal 5-phosphate methods is better than no harmonised RI.2,3 The six RIs have now been formally endorsed by AACB and RCPA and implementation can proceed. Further work is underway to harmonise RIs for albumin, urea, and urate and also several immunoassay analytes including thyroid stimulating hormone, growth hormone, and insulin-like growth factor-1.
The other three articles in this issue focus on the harmonisation of calculated biochemistry parameters.4,5,6 Considerable discussion has taken place already at previous harmonisation workshops and elsewhere, about the need for calculations to be harmonised across laboratories. However, harmonisation of calculated parameters is not as straightforward as one might think. Consideration must be given to the choice of units, the terminology, the formula to use and, importantly, the measurement uncertainty, since several analytes may be measured to obtain a calculation.
The formal SI unit for osmolality is actually mmol/kg. For the sake of harmonisation, in these three articles the AACB Calculations Working Party chaired by David Hughes has used “mOsm/kg” for osmolality, calculated osmolality and osmolal gap. This is the current recommendation of the Pathology Information, Terminology and Units Standardisation (PITUS) Project. But is this correct? To the best of our knowledge, while there have been efforts to survey the formulas used by laboratories in Australasia for calculated osmolality and osmolal gap, there has been no attempt to survey the units being used.7 We are at least fortunate in the case of osmolality that these units all result in the same numeric result with no conversion factor required.
As for the calculation, the priority for consistency and patient safety is for the same calculation to be used in all laboratories. As is discussed in this issue, laboratories are therefore encouraged to align their calculated osmolality formula to that of Smithline-Gardner [Calculated Osmolality = 2(Na) + Glucose + Urea].5
The articles in this issue are further indication that progress is being made but as more analytes are being added to the “done” list, there are still many more issues under discussion and yet to be discussed. The harmonisation work continues.
References
- 1.Koerbin G, Tate JR, on behalf of the AACB Committee for Common Reference Intervals Harmonising adult reference intervals in Australia and New Zealand – the continuing story. Clin Biochem Rev. 2016;37:121–9. [PMC free article] [PubMed] [Google Scholar]
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