scholarly journals A simple transformation independent method for outlier definition

2018 ◽  
Vol 56 (9) ◽  
pp. 1524-1532 ◽  
Author(s):  
Martin Berg Johansen ◽  
Peter Astrup Christensen
Keyword(s):  
Detection Method ◽  
Reference Intervals ◽  
Independent Method ◽  
Medical Laboratories ◽  
Simple Transformation ◽  
Reference Limits ◽  
Definition Of ◽  
Box Cox Transformation ◽  
Better Than

AbstractBackground:Definition and elimination of outliers is a key element for medical laboratories establishing or verifying reference intervals (RIs). Especially as inclusion of just a few outlying observations may seriously affect the determination of the reference limits. Many methods have been developed for definition of outliers. Several of these methods are developed for the normal distribution and often data require transformation before outlier elimination.Methods:We have developed a non-parametric transformation independent outlier definition. The new method relies on drawing reproducible histograms. This is done by using defined bin sizes above and below the median. The method is compared to the method recommended by CLSI/IFCC, which uses Box-Cox transformation (BCT) and Tukey’s fences for outlier definition. The comparison is done on eight simulated distributions and an indirect clinical datasets.Results:The comparison on simulated distributions shows that without outliers added the recommended method in general defines fewer outliers. However, when outliers are added on one side the proposed method often produces better results. With outliers on both sides the methods are equally good. Furthermore, it is found that the presence of outliers affects the BCT, and subsequently affects the determined limits of current recommended methods. This is especially seen in skewed distributions. The proposed outlier definition reproduced current RI limits on clinical data containing outliers.Conclusions:We find our simple transformation independent outlier detection method as good as or better than the currently recommended methods.

Recommendation for the review of biological reference intervals in medical laboratories

2016 ◽  
Vol 54 (12) ◽  
Author(s):  
Joseph Henny ◽  
Anne Vassault ◽  
Guilaine Boursier ◽  
Ines Vukasovic ◽  
Pika Mesko Brguljan ◽  
...  
Keyword(s):  
Expert Panel ◽  
Clinical Chemistry ◽  
Simple Procedure ◽  
Reference Population ◽  
Reference Intervals ◽  
Medical Laboratories ◽  
Reference Limits ◽  
Original Procedure ◽  
Selection Of

AbstractThis document is based on the original recommendation of the Expert Panel on the Theory of Reference Values of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC), updated guidelines were recently published under the auspices of the IFCC and the Clinical and Laboratory Standards Institute (CLSI). This document summarizes proposals for recommendations on: (i) The terminology, which is often confusing, noticeably concerning the terms of reference limits and decision limits. (ii) The method for the determination of reference limits according to the original procedure and the conditions, which should be used. (iii) A simple procedure allowing the medical laboratories to fulfill the requirements of the regulation and standards. The updated document proposes to verify that published reference limits are applicable to the laboratory involved. Finally, the strengths and limits of the revised recommendations (especially the selection of the reference population, the maintenance of the analytical quality, the choice of the statistical method used…) will be briefly discussed.

Determination of reference limits: statistical concepts and tools for sample size calculation

2014 ◽  
Vol 52 (12) ◽  
Author(s):  
Stefan Wellek ◽  
Karl J. Lackner ◽  
Christine Jennen-Steinmetz ◽  
Iris Reinhard ◽  
Isabell Hoffmann ◽  
...  
Keyword(s):  
Sample Size ◽  
Diagnostic Marker ◽  
Parametric Method ◽  
Sample Size Calculation ◽  
Reference Intervals ◽  
Healthy Population ◽  
Reference Limits

AbstractReference limits are estimators for ‘extreme’ percentiles of the distribution of a quantitative diagnostic marker in the healthy population. In most cases, interest will be in the 90% or 95% reference intervals. The standard parametric method of determining reference limits consists of computing quantities of the form

scholarly journals OPTIMIZED DETERMINATION OF 3D COORDINATES IN THE SURVEY OF INACCESSIBLE POINTS OF BUILDINGS - EXAMPLE OF APPLICATION IMPLEMENTED IN FREE SOFTWARE

2021 ◽  
Vol 27 (2) ◽  
Author(s):  
Leandro Luiz Silva de França ◽  
Andréa de Seixas ◽  
Luciene Ferreira Gama ◽  
João Naves de Moraes
Keyword(s):  
Minimum Distance ◽  
Geodetic Survey ◽  
Observation Point ◽  
Large Structures ◽  
Angle Measurements ◽  
Minimum Distances ◽  
Definition Of ◽  
Intersection Method ◽  
Better Than

Abstract: The forward intersection method is already widely used in the geodetic survey of coordinates of inaccessible points, especially when only angle measurements are available, in this case, also called the triangulation method. However, the mathematical solution of the 3D forward intersection with the analytical definition of spatial lines, resolved by the Minimum Distances Method, is still not widespread in the academic and professional environment. This mathematical modeling determines the 3D coordinates of a point located in the middle of the minimum distance between two or more spatial lines, which spatially "intersect" towards the observation point. This solution is more accurate than others presented in the literature because it simultaneously solves the problem of 3D determination of a point by the method of least squares, in addition to providing an estimate of the coordinate precision, which are inherent to the adjustment. This work, therefore, has the objective of explaining the Minimum Distances Method for the spatial intersection of targeted measurements with a Total Station from two or more known observation points for the 3D determination of inaccessible points located in corners of buildings. For the analysis of the method, a Python tool was developed for QGIS that calculates the 3D coordinates and generates the adjustment processing report, being applied with real observations of the Geodetic survey of the SUDENE building, in Recife-PE. The methodology developed in this work proved to be suitable for measurements of large structures, achieving spherical precision better than ±1.0 cm, following the Brazilian standards for urban cadastre.

Reference intervals developed from data for hospitalized patients: computerized method based on combination of laboratory and diagnostic data

1994 ◽  
Vol 40 (12) ◽  
pp. 2209-2215 ◽  
Author(s):  
T Kouri ◽  
V Kairisto ◽  
A Virtanen ◽  
E Uusipaikka ◽  
A Rajamäki ◽  
...  
Keyword(s):  
Mean Corpuscular Volume ◽  
Age Groups ◽  
Hemoglobin Concentration ◽  
Reference Intervals ◽  
Hospitalized Patients ◽  
Healthy Individuals ◽  
Reference Limits ◽  
Health Related ◽  
Final Group

Abstract We utilized the databases of a hospital information system to select for determination of reference values various individual hospitalized patients on the basis of their diagnoses at discharge. The nonparametric 2.5-97.5% "health-related" reference intervals were calculated for hemoglobin concentration, mean corpuscular volume (MCV), and erythrocyte count for both sexes. After excluding patients with diseases possibly affecting erythrocyte variables, we obtained a final group of 1786 women and 1450 men, ages 20-65 years, who were studied in age groups of 20-30, 30-45, 45-55, and 55-65 years. The upper reference limits of the MCV results obtained from hospitalized patients were higher than those produced conventionally from healthy individuals, as would be intuitively suggested by clinical experience. This method, based on selection by diagnosis, could be applicable to various analytes measured in hospital laboratories, provided sufficient data are available as databases.

Pediatric reference intervals of free thyroxine and thyroid stimulating hormone in three different hospitals

2018 ◽  
Vol 43 (5) ◽  
pp. 530-539
Author(s):  
Hale Aral ◽  
Ömer Faruk Özer ◽  
Hatice Onur ◽  
Ahmet Mete Çilingirtürk ◽  
İlker Tolga Özgen ◽  
...  
Keyword(s):  
Interaction Effect ◽  
Extreme Values ◽  
Age Groups ◽  
Reference Intervals ◽  
Thyroid Stimulating Hormone ◽  
Free Thyroxine ◽  
Reference Limits ◽  
Using Data ◽  
Box Cox Transformation ◽  
Stimulating Hormone

Abstract Objective: Using data retrieved from three different hospitals, we established indirect reference intervals of free thyroxine (FT4) and thyroid stimulating hormone (TSH) for the Centaur XP or the Immulite 2000 instruments, in separate reference limits at each subset. Methods: We categorized children into seven age groups: 4–7 days, 8–15 days, 16–23 days, 24–61 days, 3–6 months, 7–36 months and 4–6 years. After a Box-Cox transformation was employed, we followed the Horn algorithm to eliminate the extreme values. Results: The remaining FT4 (11,230) and TSH (11,274) tests were statistically analyzed. We determined separate reference limits at each subset with their own 2.5th and 97.5th percentiles. The interaction effect of both hospital and age grouping on FT4 was meaningful, but there was no interaction effect on TSH. Conclusions: Pediatric FT4 and TSH test results should be interpreted via narrowed age groups, especially in the first 3 weeks of neonatal period. Our reference limits may be recommended in pediatric follow-ups, considering the conditions of prematurity, birth-weight or multiple births. Preanalytical and analytical variations related with complex molecular structure of FT4 should be taken into consideration to ensure the validity of the result.

Determination of reference intervals for serum magnesium

1990 ◽  
Vol 36 (5) ◽  
pp. 756-758 ◽  
Author(s):  
G O Duncanson ◽  
H G Worth
Keyword(s):  
Alkaline Phosphatase ◽  
Gaussian Distribution ◽  
Parametric Analysis ◽  
Serum Magnesium ◽  
Reference Interval ◽  
Reference Intervals ◽  
Age Related ◽  
Reference Limits ◽  
Males And Females

Abstract Using a discrete analyzer and a dye-binding method, we measured magnesium in 800 patients' samples received for routine analysis. By excluding data from samples for which the calcium and (or) alkaline phosphatase values were outside defined reference limits, we established a reference interval for magnesium. Because the data showed a gaussian distribution, we could use parametric analysis to establish age-related intervals for both males and females.

DYNAMIC ADAPTIVE AUTONOMY IN MULTIAGENT SYSTEMS: REPRESENTATION AND JUSTIFICATION

2001 ◽  
Vol 15 (03) ◽  
pp. 405-433 ◽  
Author(s):  
K. SUZANNE BARBER ◽  
CHERYL E. MARTIN
Keyword(s):  
Multiagent System ◽  
Agent Based ◽  
Performance Improvements ◽  
Adaptive Agent ◽  
Series Of Experiments ◽  
Run Time ◽  
Definition Of ◽  
System Operating ◽  
Better Than

Autonomy is an often cited but rarely agreed upon agent characteristic. Although no definition of agent autonomy is universally accepted, the concept of adaptive autonomy promises increasingly flexible and robust agent-based systems. In general, adaptive autonomy gives agents the ability to seek help for problems or take initiative when otherwise they would be constrained by their design to follow some fixed procedures or rules for interacting with other agents. In order to access these benefits, this article provides a core definition and representation of agent autonomy designed to support the implementation of adaptive agent autonomy. This definition identifies "decision-making control" governing the determination of agent goals and tasks as the key dimension of agent autonomy. In order to gain run-time flexibility and any associated performance improvements, agents must be able to dynamically adapt their autonomy during system operation. This article justifies the implementation of dynamic adaptive autonomy through a series of experiments showing that a multiagent system operating under dynamic adaptive autonomy performs better than a multiagent system operating under fixed autonomy for the same changing run-time conditions.

scholarly journals Determination of indirect reference intervals of vitamin B12 for outpatients admitted to primary healthcare centers

2020 ◽  
Vol 44 (1) ◽  
pp. 11-16
Author(s):  
Esin Avci ◽  
Diler Aslan
Keyword(s):  
Vitamin B12 ◽  
Primary Healthcare ◽  
Clinical Chemistry ◽  
Age Groups ◽  
Vitamin B12 Deficiency ◽  
Reference Intervals ◽  
Microcytic Anemia ◽  
Reference Limits ◽  
B12 Deficiency

Abstract Background Vitamin B12 deficiency is still an important nutritional problem worldwide. There is no consensus on the reference intervals (RIs) for vitamin B12. In order to establish vitamin B12 RIs, we used the database obtained from a primary healthcare organization and estimated region-specific intervals. Methods Vitamin B12 results were collected from our laboratory information system (LIS) between January 2014 and July 2014. We excluded the results of the individuals who had megaloblastic and microcytic anemia. After outlier detection and exclusion, we estimated the RIs of the “1–12, 13–18, 19–64 and 65 +” age groups according to the International Federation of Clinical Chemistry (IFCC) method. Statistical differences were examined between groups. Results The reference limits and 90% confidence intervals (CIs) (n = 14,748, 3790 male, age: 1–96; 10,958 female, age: 1–115) were estimated with 90% CIs as 106 (104–107)–393 (391–395) pmol/L. We also estimated the reference limits of the “1–12, 13–18, 19–64 and 65 +” age groups to be 127–459, 108–398, 106–384 and 104–426 pmol/L, respectively. There was no difference between genders in all age groups. Conclusions Both the lower and upper limits of the estimated RIs were found to be lower than the reference limits recommended by the manufacturer. Our findings revealed that the RIs of vitamin B12 should be given for the “1–12, 13–18, 19–64 and 65 +” age groups separately. The big data obtained from laboratories should be used for the determination of its population health status. As our population is composed of outpatients, the estimated vitamin B12 RIs may establish the basic information for the examination of our population for vitamin B12 deficiency.

scholarly journals Reference Intervals for Platelet Counts in the Elderly: Results from the Prospective SENIORLAB Study

2020 ◽  
Vol 9 (9) ◽  
pp. 2856
Author(s):  
Wolfgang Hermann ◽  
Lorenz Risch ◽  
Chris Grebhardt ◽  
Urs E. Nydegger ◽  
Benjamin Sakem ◽  
...  
Keyword(s):  
The Elderly ◽  
Population Based ◽  
Reference Intervals ◽  
Specific Population ◽  
Platelet Counts ◽  
Reference Limits ◽  
Male Patients ◽  
Age And Sex ◽  
Age Independent

Currently, age- and sex-independent reference limits (RLs) are frequently used to interpret platelet counts in seniors. We aimed to define and validate reference intervals (RIs) for platelet counts within the framework of the prospective SENIORLAB study. Subjectively healthy Swiss individuals aged 60 years and older were prospectively included and followed for morbidity and mortality. Participants who had circumstances known to affect platelet counts were excluded. The obtained RIs were validated with indirect statistical methods. Frequencies of abnormal platelet counts in a population-based setting, including 41.5% of the entire age-specific population of the Principality of Liechtenstein, were compared by using age- and sex-independent RIs and the RLs obtained in the present study. For males (n = 542), 95% RIs for platelet counts were defined as follows: 150–300 × 109/L (60–69 years); 130–300 × 109/L (70–79 years); and 120–300 × 109/L (80 years and above). For females (n = 661), the consolidated age-independent 95% RI was 165–355 × 109/L. These RI values were validated by indirect RI determination of 51,687 (30,392 female/21,295 male) patients of the same age. Age- and sex-independent RIs exhibited imbalanced frequencies of abnormal platelet counts between the two sexes, which were corrected by introducing age- and sex-specific RLs. In conclusion, females have higher platelet counts than males. Whereas the upper RL for males remains constant, the lower RL decreases with age. We propose to abandon the practice of employing sex- and age-independent RL for platelet counts in the elderly.

A study on reference interval transference via linear regression

2019 ◽  
Vol 58 (1) ◽  
pp. 116-129
Author(s):  
Runqing Mu ◽  
Ke Yun ◽  
Xiaoou Yu ◽  
Shitong Cheng ◽  
Ming Ma ◽  
...  
Keyword(s):  
Linear Regression ◽  
Least Squares Method ◽  
Reference Interval ◽  
Reference Intervals ◽  
Regression Equation ◽  
Small Samples ◽  
Healthy Individuals ◽  
Test Number ◽  
Reference Limits ◽  
Better Than

Abstract Background Reference intervals (RIs) transference can expand the applicability of established RIs. However, the study on transference methodology is insufficient, and RIs validation based on small samples cannot adequately identify transferred risk under complex situations. This study aimed to find appropriate conditions to ensure the effect of transference. Methods We established the RIs of Roche and Beckman systems for 27 analytes based on 681 healthy individuals. Roche RIs were converted into the Beckman RIs using linear regression (least squares method) which is divided into two methods – Methodref (500 test numbers with relatively narrow data range) and Methodep (80 test numbers with relatively wide data range). Taking the RIs established by Beckman results as standard, we assessed the accuracy, precision and trueness of transferred results under various conditions. Results A total of 29.6% and 48.1% of analytes were consistent between the two systems for the lower and upper reference limits, respectively. The concordance rates between transferred and measured RIs for Methodref were up to 74.1% and 92.6%, which were better than Methodep (44.4% and 59.3%). The CV of transferred reference limits decreased gradually with increasing test number under the same data range. For most analytes, excluding some electrolyte tests, we could obtain accurate results when r > 0.800 and the test number was sufficient regardless of the regression equation types. Conclusions Transferability of RIs is affected by many factors, such as correlation, test number, regression equation type, and quality requirement. To reduce the risk of transference, it is very important to select right method with reasonable conditions.

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