scholarly journals Confidence interval for quantiles and percentiles

2018 ◽  
Vol 29 (1) ◽  
pp. 5-17 ◽  
Author(s):  
Cristiano Ialongo
Keyword(s):  
Confidence Interval ◽  
Laboratory Medicine ◽  
Reference Intervals ◽  
Population Parameter ◽  
Statistical Tools ◽  
Underlying Distribution ◽  
Performance Specification ◽  
Performance Specifications ◽  
And Performance ◽  
Sample Estimate

Quantiles and percentiles represent useful statistical tools for describing the distribution of results and deriving reference intervals and performance specification in laboratory medicine. They are commonly intended as the sample estimate of a population parameter and therefore they need to be presented with a confidence interval (CI). In this work we discuss three methods to estimate CI on quantiles and percentiles using parametric, nonparametric and resampling (bootstrap) approaches. The result of our numerical simulations is that parametric methods are always more accurate regardless of sample size when the procedure is appropriate for the distribution of results for both extreme (2.5th and 97.5th) and central (25th, 50th and 75th) percentiles and corresponding quantiles. We also show that both nonparametric and bootstrap methods suit well the CI of central percentiles that are used to derive performance specifications through quality indicators of laboratory processes whose underlying distribution is unknown.

scholarly journals From prescription to performance: international trends on concrete specifications and the Brazilian perspective

2010 ◽  
Vol 3 (4) ◽  
pp. 420-431
Author(s):  
J. Tanesi ◽  
M. G. da Silva ◽  
V. Gomes ◽  
G. Camarini
Keyword(s):  
Materials Selection ◽  
Performance Specification ◽  
Construction Methods ◽  
Performance Requirements ◽  
International Trends ◽  
Innovative Solutions ◽  
Performance Specifications ◽  
Hand Performance ◽  
Hardened Properties ◽  
And Performance

There are two types of specifications: prescriptive and performance based. The prescriptive specifications focus on materials properties, materials proportions, mixing and transporting procedures and on a variety of processes, such as placing and curing. In these specifications, the concrete desired performance it is not necessarily described. On the other hand, performance specifications stipulate what is required from the product and do not prescribe how the product should be produced. In other words, they focus on the desired performance rather than on the concrete ingredients, materials selection, proportioning or construction methods. These are the responsibility of those individuals who contractually have to comply with the specifications. In this case, con- crete is defined in terms of measurable fresh and hardened properties and durability and as there are no restrictions regarding materials and their proportions in the performance specifications, innovative solutions may be used in order to achieve the performance requirements. Currently, most concrete specifications are predominantly prescriptive with some performance requirements. Nevertheless, there is a consensus that in order to extend the service life of concrete structures, this has to be changed. This paper gives an overview of the international specifica- tions and describes the international efforts on the performance specification implementation in the concrete industry.

Evaluation of the ARKRAY HA-8190V instrument for HbA1c

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Eline A.E. van der Hagen ◽  
Sanne Leppink ◽  
Karin Bokkers ◽  
Carla Siebelder ◽  
Cas W. Weykamp
Keyword(s):  
Quality Assessment ◽  
Concentration Level ◽  
External Quality Assessment ◽  
Clinical Samples ◽  
Diabetic Patients ◽  
External Quality ◽  
Target Values ◽  
Performance Specifications ◽  
Certification Programme ◽  
And Performance

Abstract Objectives Hemoglobin A1c (HbA1c) is a valuable parameter in the monitoring of diabetic patients and increasingly in diagnosis of diabetes. Manufacturers continuously optimize instruments, currently the main focus is to achieve faster turnaround times. It is important that performance specifications remain of high enough standard, which is evaluated in this study for the new ARKRAY HA-8190V instrument. Methods The Clinical and Laboratory Standards Institute (CLSI) protocols EP-5, EP-9 and EP-10 were applied to investigate imprecision, bias and linearity. In addition potential interferences, performance in External Quality Assessment (EQA) and performance against the HA-8180V instrument in 220 clinical samples was evaluated. Results The HA-8190V demonstrates a CV of ≤0.8% in IFCC SI units (≤0.6% National Glycohemoglobin Standardization Program [NGSP]) at 34 and 102 mmol/mol levels (5.3 and 11.5% NGSP) and a bias of −0.1 mmol/mol (−0.01% NGSP) at a concentration of 50 mmol/mol (6.7% NGSP), but with a significant slope as compared to target values. This results in a bias of −1.0 and 0.9 mmol/mol (−2.0 and 0.9% NGSP) at the 30 and 70 mmol/mol (4.9 and 8.6% NGSP) concentration level. Simulation of participation in the IFCC certification programme results in a Silver score (bias −0.1 mmol/mol, CV 1.1%). Interference in the presence of the most important Hb variants (AS, AC, AE, AD) and elevated HbA2 and HbF concentrations is less than 3 mmol/mol (0.3% NGSP) at a concentration of 50 mmol/mol (6.7% NGSP). Conclusions Analytical performance of the HA-8190V is very good, especially with respect to precision and HbA1c quantification in the presence of the most common Hb variants.

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