The CELTIC ranges project (comprehensive and effective laboratory test reference intervals for Irish children) methodology and results for renal profile tests in plasma on the Roche modular system.

Background: The CELTIC ranges project aims to deliver a comprehensive range of reference intervals for commonly ordered laboratory investigations suitable for use in an Irish population as well as enabling comparison with relevant international studies. In this paper, we describe our methodology used throughout the entire project and present paediatric reference intervals for renal profile tests in plasma (sodium, potassium, urea and creatinine).

Methods: 1023 children aged up to 17 years were recruited from our hospital's general practitioner paediatric phlebotomy clinic. Clinical chemistry analyses were performed on the Roche modular system and statistical analysis was completed in line with CLSI guideline EP28-A3c.

Results: The plasma reference interval for sodium for ages 0.45-16.99 years was 137-143 mmol/L in 1000 subjects (combined genders). For plasma potassium, the corresponding ranges between 1 and 16.99 years (combined genders) were 3.6-4.8 mmol/L. Apart from neonates and in keeping with other studies, age partitioning for electrolytes was not required. Data for plasma creatinine (enzymatic methodology) and urea is also presented and, as anticipated, required partitioning for both age and gender.

Conclusions: Our renal profile findings are broadly consistent with those of international studies, for example, CALIPER, HAPPI, NORDIC, PRINCE and KiGGs. Moreover, the CELTIC ranges study is also based on over 1000 subjects whose samples were analysed on the widely used Roche modular analytics system. We also expect the findings will improve knowledge of children's metabolic health in Ireland.