The number of replicates, and pooling versus individual measurements for analytical imprecision calculations: Does it matter?

2020 ◽  
Vol 49 (1) ◽  
pp. 112-118 ◽  
Author(s):  
Fernando Tecles ◽  
Alberto Muñoz ◽  
José J Cerón ◽  
Kathleen Freeman
Keyword(s):  
Analytical Imprecision

Screening for haemochromatosis: Influence of analytical imprecision, diagnostic limit and prevalence on test validity

1991 ◽  
Vol 51 (2) ◽  
pp. 143-148 ◽  
Author(s):  
P. Wiggers ◽  
J Dalhøj ◽  
P. Hyltoft Petersen ◽  
O. Blaabjerg ◽  
M. Hørder
Keyword(s):  
Test Validity ◽  
Analytical Imprecision

Lactate Uptake Against a Concentration Gradient: Misinterpretation of Analytical Imprecision

2014 ◽  
Vol 31 (17) ◽  
pp. 1528-1528 ◽  
Author(s):  
Carl-Henrik Nordström ◽  
Troels Nielsen ◽  
Hans Nielsen
Keyword(s):  
Concentration Gradient ◽  
Analytical Imprecision ◽  
Lactate Uptake

Biological Variation in Urinary Excretion of Pyridinium Crosslinks: Recommendations for the Optimum Specimen

1996 ◽  
Vol 33 (1) ◽  
pp. 36-42 ◽  
Author(s):  
M Panteghini ◽  
F Pagani
Keyword(s):  
Early Morning ◽  
Reference Intervals ◽  
Biological Variation ◽  
Creatinine Ratio ◽  
Pyridinium Crosslinks ◽  
Number Of Patients ◽  
Analytical Imprecision ◽  
Optimum Specimen ◽  
The Difference ◽  
Urine Specimens

We assessed the analytical and biological variation of pyridinium crosslinks in early morning, 2 h fasting, and 24 h urine specimens from 14 healthy adults over a 1 month period. The results were expressed both in terms of pyridinoline concentration and pyridinoline/creatinine ratio. The data obtained were used to select the optimum specimen for clinical purposes. We found that: ( a) early morning specimens are preferred; ( b) results should be expressed as pyridinoline/creatinine ratio; ( c) reference intervals should be stratified according to gender; ( d) the necessary analytical imprecision (CV≤ 9%), derived from biological variation, is not easily achieved by current methods; ( e) the difference between serial results from an individual must be > 50% to be statistically significant; and ( f) assessment of risk for osteoporotic fracture by means of the pyridinium crosslink assay would, in a significant number of patients, require analysis of multiple urine specimens.

scholarly journals Clinical Evaluation of the ACS:180 Cardiac Troponin I Assay

2001 ◽  
Vol 38 (5) ◽  
pp. 509-519 ◽  
Author(s):  
Paul O Collinson ◽  
Nigel Wiggins ◽  
David C Gaze
Keyword(s):  
Endurance Training ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Troponin T ◽  
Training Group ◽  
Storage Conditions ◽  
Cardiac Troponin I ◽  
Admission Diagnosis ◽  
Coronary Syndromes ◽  
Analytical Imprecision

All patients admitted to the coronary care unit with suspected acute coronary syndromes were evaluated by serial electrocardiography and blood draws on admission and at 4 and 12h from admission. Diagnosis was based on conventional WHO criteria. Samples were measured for creatine kinase (CK), cardiac troponin T (cTnT), myoglobin, CK isoenzyme MB (CK-MB) and cardiac troponin I (cTnI). A set of samples from individuals undergoing extreme endurance training was also examined. Analytical imprecision was consistent with published quality goals. Samples were stable for cTnI under a range of storage conditions, including multiple freeze-thaw cycles. CK-MB, cTnI and cTnT were equally efficient for the diagnosis of acute myocardial infarction, irrespective of the final diagnostic criteria used. Both cTnI and cTnT were of equal efficiency in the identification of a high-risk subgroup of patients with unstable angina. Significant elevations of cTnI were not seen in an endurance-training group.

scholarly journals Analytical and diagnostic performances of a high-throughput immunoassay for SARS-CoV-2 IgM and IgG

2020 ◽  
Author(s):  
Andrea Padoan ◽  
Chiara Cosma ◽  
Paolo Zaupa ◽  
Mario Plebani
Keyword(s):  
Sensitivity And Specificity ◽  
Symptom Onset ◽  
Severe Disease ◽  
Onset Time ◽  
Time Frame ◽  
Serum Samples ◽  
Time Period ◽  
Analytical Imprecision ◽  
Range Of Values

BackgroundAbstractReliable SARS-CoV-2 serological assays are required for diagnosing infections, for the serosurveillance of past exposures and for assessing the response to future vaccines. In this study, the analytical and clinical performances of a chemiluminescent immunoassays for SARS-CoV-2 IgM and IgG detection (Mindray CL-1200i), targeting Nucleocapsid (N) and receptor binding domain (RBD) portion of the Spike protein, were evaluated.MethodsPrecision and linearity were evaluated using standardized procedures. A total of 157 leftover serum samples from 81 hospitalized confirmed COVID-19 patients (38 with moderate and 43 with severe disease) and 76 SARS-CoV-2 negative subjects (44 healthcare workers, 20 individuals with rheumatic disorders, 12 pregnant women) were included in the study. In an additional series of 44 SARS-CoV-2 positive, IgM and IgG time kinetics were also evaluated in a time-period of 38 days.ResultsPrecision was below or equal to 4% for both IgM and IgG, in all the studied levels, whilst a slightly significant deviation from linearity was observed for both assays in the range of values covering the manufacturer’s cut-off. Considering a time frame ≥ 12 days post symptom onset, sensitivity and specificity for IgM were 92.3% (95%CI:79.1%-98.4%) and 92.1% (95%CI:83.6%-97.0%). In the same time frame, sensitivity and specificity for IgG were 100% (95%CI:91.0%-100%) and 93.4% (95%CI:85.3%-97.8%). The assays agreement was 73.9% (Cohen’s kappa of 0.373). Time kinetics showed a substantial overlapping of IgM and IgG response, the latter values being elevated up to 38 days from symptoms onset.ConclusionsAnalytical imprecision is satisfactory as well as the linearity, particularly when taking into account the fact that both assays are claimed to be qualitative. Diagnostic sensitivity of IgG was excellent, especially considering specimens collected ≥12 days post symptom onset. Time kinetics suggest that IgM and IgG are detectable early in the course of infection, but the role of SARS-CoV-2 antibodies in clinical practice still requires further evaluations.

scholarly journals Postanalytical External Quality Assessment of Urine Albumin in Primary Health Care: An International Survey

2008 ◽  
Vol 54 (10) ◽  
pp. 1630-1636 ◽  
Author(s):  
Kristin M Aakre ◽  
Geir Thue ◽  
Sumathi Subramaniam-Haavik ◽  
Tone Bukve ◽  
Howard Morris ◽  
...  
Keyword(s):  
Diabetes Patient ◽  
Critical Difference ◽  
Albumin Creatinine Ratio ◽  
Spot Urine ◽  
Urine Albumin ◽  
Primary Health ◽  
Analytical Imprecision ◽  
Measurement Units ◽  
First Time

Abstract background: Microalbuminuria (MA) is recognized as an important risk factor for cardiovascular and renal complications in diabetes. We sought to evaluate how screening for MA is conducted and how urine albumin (UA) results are interpreted in primary care internationally. methods: General practitioners (GPs) received a case history–based questionnaire depicting a male type 2 diabetes patient in whom UA testing had not been performed. Questions were related to type of urine sample used for UA testing, need for a repeat test, whether UA testing was performed in the office laboratory, and what changes in UA results were considered clinically important [critical difference (CD)]. Participants received national benchmarking feedback reports. results: We included 2078 GPs from 9 European countries. Spot urine samples were used most commonly for first time office-based testing, whereas timed collections were used to a larger extent for hospital-based repeat tests. Repeat tests were requested by 45%–77% of GPs if the first test was positive. Four different measurement units were used by 70% of participants in estimating clinically important changes in albumin values. Stated CDs varied considerably among GPs, with similar variations in each country. A median CD of 33% was considered clinically important for both improvement and deterioration in MA, corresponding to an achievable analytical imprecision of 14%, when UA is reported as an albumin/creatinine ratio. conclusions: Guidelines on diagnosing MA are followed only partially, and should be made more practicable, addressing issues such as type of samples, measurement units, and repeat tests.

Improved procedure for measuring gamma-glutamyltransferase isoenzymes in serum.

1988 ◽  
Vol 34 (2) ◽  
pp. 419-422 ◽  
Author(s):  
L Sacchetti ◽  
G Castaldo ◽  
G Fortunato ◽  
F Salvatore
Keyword(s):  
Scattered Light ◽  
Density Lipoprotein ◽  
Normal Subjects ◽  
Total Activity ◽  
Coumarin Derivative ◽  
Very Low Density Lipoproteins ◽  
Gamma Glutamyltransferase ◽  
Analytical Imprecision ◽  
Hepatobiliary Diseases ◽  
Electrophoretic Procedure

Abstract In this electrophoretic procedure for measuring isoenzymes of gamma-glutamyltransferase, patterns obtained are highly reproducible and the analytical imprecision (CV) ranges from 1.10% to 6.17%. A cellulose acetate support is used, at 220 V for 40 min. Sharply resolved isoenzyme bands were made visible by fluorescence scattered light, formed by use of a coumarin derivative as donor substrate. Two bands were observed for sera from normal subjects; four bands were variably present in sera from patients with different hepatobiliary diseases. Detection of the latter was satisfactory, down to a total activity in serum of 8-10 U/L. Three of the pathological bands were associated with low- and (or) very-low-density lipoproteins, whereas a major fraction of one of the normal bands in cirrhotic sera precipitated with high-density lipoprotein. The bands in normal sera, and one of the abnormal bands, did not.

Robotic Automation of Cyclosporine Analysis in Whole Blood

1992 ◽  
Vol 38 (8) ◽  
pp. 1440-1443 ◽  
Author(s):  
J W Holman ◽  
R A Felder
Keyword(s):  
Whole Blood ◽  
Solid Phase ◽  
Internal Standard ◽  
Sample Tube ◽  
Organ Rejection ◽  
Analytical Recovery ◽  
Analytical Imprecision ◽  
Blood Specimens ◽  
Methods Analytical ◽  
Robotic Automation

Abstract Cyclosporin A (CsA) is currently the most selective immunosuppressant used clinically to prevent organ rejection after transplantation. We used a reprogrammable robot, the Benchmate (Zymark Inc., Hopkinton, MA), to automate much of the sample preparation involved in solid-phase extraction of CsA. Lysed whole-blood specimens containing previously added internal standard were placed on the Benchmate in the specimen-holding area, and a C18 Bond-Elut column was placed in the top of the sample tube. Specimen extraction from this point was handled automatically by the Benchmate, after which we manually injected the sample into the HPLC system for quantification. Analytical recovery of CsA in two concentrations of calibrator was similar for the manual and Benchmate methods. Analytical imprecision for the Benchmate was less than for manual extraction: within-run imprecision (CV) was less than 8% at either concentration. Between-run imprecision, determined by having the Benchmate extract CsA from two specimens each day for 20 days, was less than 9%. Patients' specimens were extracted manually (x) or by using the Benchmate robot (y); the results, compared by linear regression, agreed well: (y = 0.99 (SD 0.02)x + 2.6 (SD 2.8) micrograms/L (Sy[x = 7.59 micrograms/L, n = 27). We conclude that the Benchmate usefully reduces the manual steps necessary to extract specimens before HPLC analysis for CsA.

Comparing the Power of Quality-Control Rules to Detect Persistent Increases In Random Error

1992 ◽  
Vol 38 (3) ◽  
pp. 364-369 ◽  
Author(s):  
C A Parvin
Keyword(s):  
Quality Control ◽  
Error Detection ◽  
Statistical Evaluation ◽  
Poor Performance ◽  
Operating Conditions ◽  
Evaluation Approach ◽  
Control Rules ◽  
Stable Operating ◽  
Alternative Approach ◽  
Analytical Imprecision

Abstract This paper continues an investigation into the merits of an alternative approach to the statistical evaluation of quality-control rules. In this report, computer simulation is used to evaluate and compare quality-control rules designed to detect increases in within-run or between-run imprecision. When out-of-control conditions are evaluated in terms of their impact on total analytical imprecision, the error detection ability of a rule depends on the relative magnitudes of the between-run and within-run error components under stable operating conditions. A recently proposed rule based on the F-test, designed to detect increases in between-run imprecision, is shown to have relatively poor performance characteristics. Additionally, several issues are examined that have been difficult to address with the traditional evaluation approach.

Intraindividual variation of glycohemoglobin: implications for interpretation and analytical goals

1993 ◽  
Vol 39 (11) ◽  
pp. 2305-2308 ◽  
Author(s):  
G Phillipou ◽  
P J Phillips
Keyword(s):  
Weighted Average ◽  
Affinity Column ◽  
Time Interval ◽  
Short Term ◽  
Intraindividual Variation ◽  
Clinical Control ◽  
Significant Difference ◽  
Patients With Diabetes ◽  
Analytical Imprecision

Abstract Intraindividual variation (CVi) for glycohemoglobin (GHb) was estimated from serial measurements in patients with diabetes in either stable or variable clinical control. GHb determinations were performed by an affinity column procedure with an analytical imprecision of 4.9% (weighted average; GHb 8.2-14.7%). Within the groups of patients, both a short- (28-32 days) and long-term (approximately 85 days) sampling protocol was used. The derived CVi for each category was 4.2% (n = 16, stable, short-term), 7.1% (n = 23, stable, long-term), 5.1% (n = 13, variable, short-term), and 9.8% (n = 21, variable, long-term). The mean GHb within each category was similar (approximately 11%), and there was no statistically significant difference in GHb values between categories. The results establish that the CVi for GHb is affected by both clinical control and the sampling time interval. These findings have important implications for the estimation of significant differences between serial GHb measurements and the setting of appropriate analytical precision goals.

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