Pediatric reference intervals determined in ambulatory and hospitalized children and juveniles.

OBJECTIVES: The aim of this study was to determine reference intervals in children and juveniles with nine recently developed and widely used laboratory methods. 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 degrees 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. RESULTS: 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. CONCLUSION: Proposals for reference intervals were derived from the central 95 percentile values.

Reference intervals for serum creatinine concentrations: assessment of available data for global application.

BACKGROUND: Reference intervals for serum creatinine remain relevant despite the current emphasis on the use of the estimated glomerular filtration rate for assessing renal function. Many studies on creatinine reference values have been published in the last 20 years. Using criteria derived from published IFCC documents, we sought to identify universally applicable reference intervals for creatinine via a systematic review of the literature. METHODS: Studies were selected for inclusion in the systematic review only if the following criteria were met: (a) reference individuals were selected using an "a priori" selection scheme, (b) preanalytical conditions were adequately described; (c) traceability of the produced results to the isotope dilution-mass spectrometry (IDMS) reference method was demonstrated experimentally, and (d) the collected data received adequate statistical treatment. RESULTS: Of 37 reports dealing specifically with serum creatinine reference values, only 1 report with pediatric data and 5 reports with adult data met these criteria. The primary reason for exclusion of most papers was an inadequate demonstration of measurement traceability. Based on the data of the selected studies, we have collated recommended reference intervals for white adults and children. CONCLUSION: Laboratories using methods producing traceable results to IDMS can apply the selected reference intervals for serum creatinine in evaluating white individuals.

Creation of the necessary analytical quality for generating and using reference intervals.

This is a brief compilation of criteria on analytical quality that are prerequisites for the establishment and use of reference intervals in laboratory medicine. In this context, analytical quality is characterized by the precision, accuracy and long-term stability of laboratory methods performed with diagnostic kits, including their application on various instrument platforms. Systematically, analytical quality can be differentiated into quality of the method and its performance, and quality of long-term use. Factors influencing these types of quality in the development of diagnostic kits are discussed. The responsibility for maintaining analytical quality is shared by the two parties involved in the provision and use of reference intervals: The manufacturers of diagnostic kits are committed to providing complete description and traceability of their methods, whereas users must consider the effects of physiological, biometrical, preanalytical and analytical influences on the reference interval.

Determination of reference intervals for serum creatinine, creatinine excretion and creatinine clearance with an enzymatic and a modified Jaffé method.

OBJECTIVES: The aim of this study was to determine the reference intervals for serum creatinine, the renal creatinine output and the creatinine clearance (CrCl) with two new methods for accurate creatinine determination. METHODS: The reference population consisted of 252 healthy subjects (127 males and 125 females) at the age between 18 and 74 years, median 27. Urine was collected for exactly 24 h. Creatinine in serum and urine was measured with an enzymatic assay ("Creatinine Plus") and a modification of the kinetic Jaffé reaction, named "Jaffé compensated". RESULTS: Reference values for serum creatinine were almost identical to previously published ones obtained with the same methods: 0.73-1.18 and 0.55-1.02 mg/dl for males and females, respectively, with the enzymatic, 0.72-1.16 and 0.55-0.96 mg/dl with the compensated Jaffé method (Jcomp). CrCl values were normally distributed and showed no gender difference in contrast to some previous studies. The reference interval for the entire group was found to be 66-143 ml/min with the enzymatic assay and 71-151 ml/min with the chemical one.