Laboratory assays in pediatric endocrinology: common aspects

With a rapidly expanding armamentarium of tests, endocrinologists need the ability to critically assess a laboratory assay and to understand its application. There are numerous important issues to consider. Analytical validation ensures that an assay meets standards for sensitivity, specificity and reproducibility. Clinical validation allows the results of a test to be effectively applied to a given clinical situation. Antibody-based endocrine assays are typically either competitive or non-competitive. For competitive assays, an interference that decreases signal will lead to an apparent increase in the analyte concentration, while an interference that decreases signal in a non-competitive assay will cause an apparent decrease in the analyte concentration. Mass spectrometry is rapidly increasing in use and has its own promises and pitfalls. Numerous methods exist for determining reference intervals, each giving different results. Making endocrine diagnoses based on such intervals may be overly simplistic and collaboration between clinicians and the laboratory to establish clinical thresholds would be far more informative.