Pediatric reference intervals determined in ambulatory and hospitalized children and juveniles

The aim of this study was to determine reference intervals in children and juveniles with nine recently developed and widely used laboratory methods. More than 800 ambulatory and hospitalized individuals of the University pediatry were carefully selected according to clinical status and chemical profile in an a posteriori process over a period of two and a half years. The reference group with well-balanced gender proportions and steady age distribution between 1 day and 17 years was subdivided in five age classes. The laboratory methods were: the enzyme methods ALT, AST, LDH and GGT, all reliably reference standardized with traceability to the IFCC reference methods at 37 °C; ALT and AST without pyridoxal-phosphate activation; ALP as not yet approved IFCC method; the soluble transferrin receptor (sTfR) and ferritin, the latter being the only heterogeneous procedure. The results confirm in most cases the typical age concentration relationship of the measured quantities documented for similar methods. In some critical cases, in particular for sTfR and ferritin, the study produces limits which differ distinctly from those earlier reported. Gender differentiation was outlined according to statistical calculations. Proposals for reference intervals were derived from the central 95 percentile values.