scholarly journals Effect of the Reporting-Interval Size on Critical Difference Estimation: Beyond “2.77”

2006 ◽  
Vol 52 (5) ◽  
pp. 880-885 ◽  
Author(s):  
Graham Ross Dallas Jones
Keyword(s):  
Linear Increase ◽  
Biological Variation ◽  
Analyte Concentration ◽  
Critical Difference ◽  
Analytical Precision ◽  
Interval Size ◽  
Assay Precision ◽  
Spreadsheet Application ◽  
Made In

Abstract Background: The reporting interval is the bin size used to report numerical pathology results and must be determined for every analyte. The influence of the size of the reporting interval on the critical difference (CD) between two results from the same patient has not been addressed previously. Methods: The effect of changing the reporting-interval size (RIS) on CDs was modeled by use of a spreadsheet application. The findings were applied to data on CDs with analytical precision values from our laboratory. Results: As the RIS increases relative to the combined analytical and within-person biological variation, there is an approximately linear increase in the CD from the value determined by use of published techniques. The revised estimate is as follows: CD = 21/2 × z × (SDa2 + SDi2)1/2 + 1.5 × RIS, where CD, SD, and RIS are all in the same units. This effect is seen for any probability associated with the critical difference and for both uni- and bidirectional changes. Conclusions: The choice of reporting interval should be made in the light of assay requirements. Where there is a clinical need for detection of small changes in analyte concentration, the reporting interval should be kept small relative to the combined variation attributable to assay precision and within-person biological variation.

scholarly journals Critical Difference and Biological Variation in Biomarkers of Oxidative Stress and Nutritional Status in Athletes

PLoS ONE ◽  
2016 ◽  
Vol 11 (3) ◽  
pp. e0149927 ◽  
Author(s):  
Nathan A. Lewis ◽  
John Newell ◽  
Richard Burden ◽  
Glyn Howatson ◽  
Charles R. Pedlar
Keyword(s):  
Oxidative Stress ◽  
Nutritional Status ◽  
Biological Variation ◽  
Critical Difference ◽  
Biomarkers Of Oxidative Stress

Application of the CLSI EP15-A3 Guideline as an Alternative Troubleshooting Tool for Verification of Assay Precision

2019 ◽  
Vol 152 (Supplement_1) ◽  
pp. S88-S88
Author(s):  
Jose Jara Aguirre ◽  
Karl Ness ◽  
Alicia Algeciras-Schimnich
Keyword(s):  
Quality Control ◽  
Carcinoembryonic Antigen ◽  
Laboratory Investigation ◽  
Analysis Of Variance ◽  
Experimental Approach ◽  
Biological Variation ◽  
Analytical Performance ◽  
Microsoft Excel ◽  
Before And After ◽  
Assay Precision

Abstract Introduction The CLSI EP15-A3 guideline “User Verification of Precision and Estimation of Bias” provides a simple experimental approach to estimate a method’s imprecision and bias. The objective is to determine if the laboratory precision performance of repeatability (SR) and within-laboratory imprecision (SWL) are in accordance to the manufacturer specification claims (MSCs). Objectives Evaluate the utility of the EP15-A3 protocol to verify method precision during a troubleshooting investigation and after major instrument maintenance, using a carcinoembryonic antigen (CEA) immunoassay as an example. Methods CEA was performed on the Beckman Coulter DxI (Beckman Coulter, Brea, CA). Quality control (QC) levels (L1: 2.89; L2: 21.10; L3: 39.10 ng/mL) (Bio-Rad Laboratories, Irvine, CA) were used. Each QC level was measured before and after instrument maintenance as follows: five replicates per run, one run per day, and during 5 days. Imprecision estimates (IEs) for SR (%CVR) and SWL (%CVWL) were calculated by one-way analysis of variance using Microsoft Excel Analyse-it software. Estimated imprecision was compared to MSC and desirable imprecision specifications based on biological variation (BV). Results A change in the analytical performance of CEA was detected by a decreased sigma-metric indicator. After a bias problem was ruled out, the observed %CVR for L1, L2, and L3 were 7.2%, 3.7%, and 4.8%, respectively. The %CVWL were 8.3%, 5.0%, and 5.5%, which exceeded the MSC of %CVWL~4.0% to 4.5%. After a laboratory investigation, major instrument maintenance was performed by the manufacturer. The %CVR and %CVWL estimates for L1, L2, and L3 after maintenance were 3.2%, 3.8%, 3.5% and 3.9%, 4.2%, 4.0%, respectively. After maintenance, the CEA performance was consistent with the MSC for each of the levels analyzed and within the BV impression goal of %CV ≤6.4. Conclusion CLSI EP15-A3 guideline is an alternative troubleshooting tool that can be used to investigate and verify method precision performance before and after significant instrument maintenance.

scholarly journals Analytical applications of oscillatory chemical reactions: Determination of some pharmaceuticaly and biologically important compounds

2012 ◽  
Vol 66 (2) ◽  
pp. 153-164 ◽  
Author(s):  
Natasa Pejic ◽  
Slobodan Anic ◽  
Ljiljana Kolar-Anic
Keyword(s):  
Chemical Reactions ◽  
Stirred Tank ◽  
Analyte Concentration ◽  
Tank Reactor ◽  
The Past ◽  
Quantitative Characteristics ◽  
Oscillatory Chemical ◽  
Kinetics Of ◽  
Made In

Novel analytical methods for quantitive determination of analytes based on perturbations of oscillatory chemical reactions realized under open reactor conditions (continuosly fed well stirred tank reactor, CSTR), have been developed in the past twenty years. The proposed kinetic methods are generally based on the ability of the analyzed substances to change the kinetics of the chemical reactions matrix. The unambiguous correlation of quantitative characteristics of perturbations, and the amount (concentration) of analyte expressed as a regression equation, or its graphics (calibration curve), enable the determination of the unknown analyte concentration. Attention is given to the development of these methods because of their simple experimental procedures, broad range of linear regression ( 10-7 10-4 mol L-1) and low limits of detection of analytes ( 10-6 10-8 mol L1, in some cases even lower than 10-12 mol L-1). Therefore, their application is very convenient for routine analysis of various inorganic and organic compounds as well as gases. This review summarizes progress made in the past 5 years on quantitative determination of pharmaceutically and biologically important compounds.

scholarly journals Salivary Hormone Critical Difference And Biological Variation In A Professional American Football Season

2020 ◽  
Vol 52 (7S) ◽  
pp. 36-36
Author(s):  
Anthony S. Wolfe ◽  
Steven A. Basham ◽  
Bridget C. Sopeña ◽  
Melissa L. Anderson ◽  
Timothy J. Roberts ◽  
...  
Keyword(s):  
Biological Variation ◽  
American Football ◽  
Critical Difference

Analytical precision, biological variation, and mathematical normalization in high data density metabolomics

Metabolomics ◽  
2005 ◽  
Vol 1 (1) ◽  
pp. 75-85 ◽  
Author(s):  
Yevgeniya I. Shurubor ◽  
Ugo Paolucci ◽  
Boris F. Krasnikov ◽  
Wayne R. Matson ◽  
Bruce S. Kristal
Keyword(s):  
Biological Variation ◽  
High Data ◽  
Analytical Precision ◽  
Data Density

scholarly journals Validation of a spectrophotometric method for GGT measurement in canine urine and determination of the urine GGT-to-creatinine ratio reference interval and biological variation in 41 healthy dogs

2018 ◽  
Vol 31 (1) ◽  
pp. 33-39
Author(s):  
Nicholas P. Ilchyshyn ◽  
Elizabeth Villiers ◽  
Paola Monti
Keyword(s):  
Reference Interval ◽  
Population Based ◽  
Biological Variation ◽  
Gamma Glutamyl Transferase ◽  
Creatinine Ratio ◽  
Reference Change Value ◽  
Patients At Risk ◽  
Healthy Dogs ◽  
Assay Precision ◽  
Glutamyl Transferase

The urine gamma-glutamyl transferase (GGT)-to-creatinine ratio has been used to monitor patients at risk of acute renal injury. We validated the spectrophotometric quantification of GGT in urine in a commercial biochemistry analyzer. The assay was precise, accurate, and linear. Intra-assay precision was 3.59% in 4 samples, with GGT concentrations of 47–195 U/L. Inter-assay precision in 3 samples with activities of 11–51 U/L was 7.74%. Accuracy was 97.3%, with an absolute bias of 2.7 U/L. Urine GGT was unaffected by hematuria, hemoglobinuria, or bacteriuria. Urine GGT was stable at 20°C and 4°C for up to 3 d. Storage by freezing at −20°C resulted in a significant reduction in enzyme activity. A pH outside the range of 6.5–8 resulted in reduced GGT activity. The biological variation of urine GGT-to-creatinine ratio provided an index of individuality of 1.6, indicating that a population-based reference interval (RI) can be used. The reference change value was calculated, and an increase in consecutive measurements >43% is required to be regarded as significant. The urine GGT-to-creatinine ratio RI obtained in a population of 41 healthy dogs was 8.5–28.5 U/g.

scholarly journals Estimates of Within-Subject Biological Variation Derived from Pathology Databases: An Approach to Allow Assessment of the Effects of Age, Sex, Time between Sample Collections, and Analyte Concentration on Reference Change Values

2019 ◽  
Vol 65 (4) ◽  
pp. 579-588 ◽  
Author(s):  
Graham Ross Dallas Jones
Keyword(s):  
Clinical Laboratory ◽  
Biological Variation ◽  
Clinical Environment ◽  
Analyte Concentration ◽  
Regression To The Mean ◽  
Statistical Process ◽  
Reference Change Value ◽  
First Results ◽  
The Mean ◽  
Number Of Individuals

Abstract BACKGROUND Within-subject biological variation data (CVI) are used to establish quality requirements for assays and allow calculation of the reference change value (RCV) for quantitative clinical laboratory tests. The CVI is generally determined using a large number of samples from a small number of individuals under controlled conditions. The approach presented here is to use a small number of samples (n = 2) that have been collected for routine clinical purposes from a large number of individuals. METHODS Pairs of sequential results from adult patients were extracted from a routine pathology database for 29 common chemical and hematological tests. Using a statistical process to identify a central gaussian distribution in the ratios of the result pairs, the total result variation for individual results was determined for 26 tests. The CVI was then calculated by removing the effect of analytical variation. RESULTS This approach produced estimates of CVI that, for most of the analytes in this study, show good agreement with published values. The data demonstrated minimal effect of sex, age, or time between samples. Analyte concentration was shown to affect the distributions with first results more distant from the population mean more likely to be followed by a result closer to the mean. DISCUSSION The process described here has allowed rapid and simple production of CVI data. The technique requires no patient intervention and replicates the clinical environment, although it may not be universally applicable. Additionally, the effect of regression to the mean described here may allow better interpretation of sequential patient results.

Within- and between-subject biological variations of follitropin, lutropin, testosterone, and sex-hormone-binding globulin in men

1993 ◽  
Vol 39 (8) ◽  
pp. 1723-1725 ◽  
Author(s):  
J Valero-Politi ◽  
X Fuentes-Arderiu
Keyword(s):  
Change Detection ◽  
Biological Variation ◽  
Sex Hormone ◽  
Sex Hormone Binding Globulin ◽  
Serum Concentrations ◽  
Hormone Binding ◽  
Critical Difference ◽  
Coefficients Of Variation ◽  
Index Of Individuality ◽  
Significant Change

Abstract The within-subject and between-subject biological variation of the serum concentrations of follitropin, lutropin, sex-hormone-binding globulin, and testosterone; the ratio between the serum concentrations of testosterone and sex-hormone-binding globulin; and the concentration of testosterone in saliva have been studied in a group of 20 men during 12 months. The between-subject coefficients of variation (CVs) were 36.0% for follitropin, 37.0% for lutropin, 42.7% for sex-hormone-binding globulin, 21.3% for testosterone in serum, 28.8% for testosterone in saliva, and 51.6% for the ratio between serum concentrations of testosterone and sex-hormone-binding globulin. The medians of the within-subject CVs for the respective analyses and ratio were 17.3%, 24.0%, 12.1%, 10.9%, 17.3%, and 9.4%. These data were used to calculate the desirable imprecision, the critical difference for significant change detection, and the index of individuality.

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