Sex Hormones and Adrenal Steroids: Biological Variation Estimated Using Direct and Indirect Methods.

Background: Biological variation (BV) data may be used to develop analytical performance specifications (APS), reference change values (RCV), and support the applicability of population reference intervals. This study estimates within-subject BV (CVI) for several endocrine biomarkers using 3 different methodological approaches.

Methods: For the direct method, 30 healthy volunteers were sampled weekly for 10 consecutive weeks.

Measurement uncertainty for clinical laboratories - a revision of the concept.

The uncertainty of a measurement result is a fundamental concept in metrology indicating the range within the "true" value of a measurement should lie. Although not commonly reported with results, the calculation of measurement uncertainty (MU) has become common in routine clinical laboratories. Interpretation of numerical pathology results is made by comparison with data from other measurements.

Effect of renal function on serum cardiac troponin T--Population and individual effects.

Background: Elevations of serum cardiac troponin T (cTnT) have been described in patients with end stage chronic kidney disease (CKD) although the mechanism is unknown, whether from increased production or decreased clearance. Less is known about cTnT in short term changes in renal function and in lesser degrees of renal impairment.

Objectives: This study aimed to investigate the effect of renal function changes on cTnT within individuals and characterise the distribution of cTnT according to renal function in the population.

Analytical performance specifications for EQA schemes - need for harmonisation.

External Quality Assurance (EQA) is a vital tool in laboratory medicine to assess individual laboratory analytical performance and also the differences between the results from different laboratories. This information is also useful for professional bodies and manufacturers as part of post-market surveillance. The process involves the measurement of one or more samples by many laboratories and then assessment of the results.