Chinese Pediatric Reference Intervals for Serum Cortisol on IMMULITE 2000

Clinical interpretation of the test results for cortisol based on continuous reference intervals with appropriate partitions improves pediatric diagnosis; however, these values are available only for Caucasians. To develop the pediatric reference intervals for Chinese population, we examined the serum cortisol levels in 1,143 healthy Chinese children aged 4–18 years (566 boys and 577 girls), using an IMMULITE 2000 Immunoassay System (Siemens Healthcare GmbH). Phlebotomy was performed at 7–9 a.m. for 284 boys and 287 girls and at 1–3 p.m. for the others. They were divided into four age groups according to the Clinical and Laboratory Standards Institute guideline EP28-A3c, with the last group further stratified according to sampling time. Separate reference intervals of 49.6–323.7, 70.9–395.3, and 90.1–448.7 nmol/L were established for children aged 4–8, 9–12, and 13–15 years, respectively. Further, reference intervals of 118.2–464.7 and 71.4–446.7 nmol/L were established for morning and afternoon cortisol levels, respectively, in children aged 16–18 years. Further studies are necessary to transfer and validate these reference intervals in other analytical systems and pediatric populations, and to allow for broader applications.