QUANTIFICATION OF THE MEASUREMENT UNCERTAINTY FOR D-DIMER ASSAY RESULTS AROUND THE CUT-OFF LEVEL: IMPROVED DECISION RULES REQUIRED?

Abstract Abstract 3186 Background Several clinical decision rules (CDRs) are available for the exclusion of acute pulmonary embolism (PE). This prospective multi-center study compared the safety and clinical utility of four CDRs (Wells rule, revised Geneva score, simplified Wells rule and simplified revised Geneva score) in excluding PE in combination with D-dimer testing. Methods Clinical probability of patients with suspected acute PE was assessed using a computerized based “black box”, which calculated all CDRs and indicated the next diagnostic step. A “PE unlikely” result according to all CDRs in combination with a normal D-dimer result excluded PE, while patients with “PE likely” according to at least one of the CDRs or an abnormal D-dimer result underwent CT-scanning. Patients in whom PE was excluded were followed for three months. Results 807 consecutive patients were included and PE prevalence was 23%. The number of patients categorized as “PE unlikely” ranged from 62% (simplified Wells rule) to 72% (Wells rule). Combined with a normal D-dimer level, the CDRs excluded PE in 22–24% of patients. The total failure rates of the CDR-D-dimer combinations were similar (1 failure, 0.5– 0.6%, upper 95% CI 2.9– 3.1%). Despite 30% of the patients had discordant CDR outcomes, PE was missed in none of the patients with discordant CDRs and a normal D-dimer result. Conclusions All four CDRs show similar safety and clinical utility for exclusion of acute PE in combination with a normal D-dimer level. With this prospective validation, the more straightforward simplified scores are ready for use in clinical practice. Disclosures: No relevant conflicts of interest to declare.

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Uncertainty of measurement and conformity assessment

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/854/1/012093 ◽

2021 ◽

Vol 854 (1) ◽

pp. 012093

Author(s):

Silvana Stajkovic ◽

Dragan Vasilev ◽

Mirjana Dimitrijevic ◽

Nedjeljko Karabasil

Keyword(s):

Decision Making ◽

Measurement Uncertainty ◽

Decision Rule ◽

Decision Rules ◽

Conformity Assessment ◽

Test Results ◽

Uncertainty Of Measurement ◽

Tolerance Limits ◽

Measurement Result ◽

Testing Laboratories

Abstract Knowledge of the measurement uncertainty of test results is fundamentally important for laboratories, their customers and all parties using and interpreting these results. In conformity assessment, a measurement result is used to decide if an item of interest conforms to a specified requirement. Because of measurement uncertainty, there is always the risk of incorrectly deciding whether or not an item conforms to a specified requirement based on the measured value of a property of the item. Conformity assessment can be quite challenging when the entity measured is so close to the tolerance limits of the specification that its uncertainty, however estimated, critically affects decision-making. In such cases, different decision rules can be used to make statements of conformity. The aim of this paper is to provide a survey of methods for the evaluation of measurement uncertainty in testing, as well as to stress the need for appropriate estimation of measurement uncertainty. This paper also aims to assist testing laboratories in understanding the different decision rules used in conformity assessment and level of risk (such as false accept and false reject) associated with the decision rule employed.

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The Simplified Geneva Score and the Utilization of the D-Dimer and Computerized Tomography for Assessing Pulmonary Embolism

Kansas Journal of Medicine ◽

10.17161/kjm.v4i4.11392 ◽

2011 ◽

Vol 4 (4) ◽

pp. 99-104

Author(s):

John H Park ◽

Cole R Spresser ◽

Jorge A Valdivia ◽

Michael J Khadavi ◽

Saikat Das ◽

...

Keyword(s):

Pulmonary Embolism ◽

Decision Rules ◽

Clinical Decision ◽

Pulmonary Emboli ◽

Clinical Decision Rules ◽

Diagnostic Decision ◽

Revised Geneva Score ◽

Effective Use ◽

Diagnostic Decision Making ◽

D Dimer

Background. Pulmonary embolism (PE) is clinically suspected in many patients who complain of shortness of breath or chest pain due to its nonspecific nature. The prevalence of PE, however, is low in this population. To assist physicians in diagnostic decision making, several clinical decision rules (CDR) have been developed. The appropriate use of these CDRs has been proven to decrease the need for expensive, time consuming, and invasive diagnostic imaging procedures. In this study, the appropriateness of D-dimer and CT usage was investigated to rule out pulmonary emboli based on the simplified Geneva score. Methods. A retrospective review was performed on 74 patients with a CT scan ordered through a pulmonary embolism (PE) protocol. Using clinical data, the patients were stratified into “unlikely” and “likely” groups for the presence of PE based on the simplification of the revised Geneva score. Scores of 0-2 were graded as “unlikely” and scores of 3 or greater were “likely.” Results. There were 45/74 (60.8%) patients in the “unlikely” group. Of these, 14/45 (31.1%) received a D-dimer; eight were normal and six elevated. Only one patient in the elevated group had evidence of a PE. Of the remaining 31(39.2%) patients in the “unlikely” group that did not receive a D-dimer, only one had a PE. The “likely” group consisted of 29 (39.2%) patients of whom six received a D-dimer. Three patients had a normal D-dimer and three had an elevated level. Neither of these two groups had a PE. Of the remaining 23 (60.8%) in the “likely” group who did not receive a D-dimer, six had a PE. Conclusions. Diagnosing pulmonary emboli using D-dimer levels and CT scans may be aided by clinical decision rules such as the simplified Geneva system. This process may lead to more effective use of medical resources.

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Selecting pregnant or postpartum women with suspected pulmonary embolism for diagnostic imaging: the DiPEP diagnostic study with decision-analysis modelling

Health Technology Assessment ◽

10.3310/hta22470 ◽

2018 ◽

Vol 22 (47) ◽

pp. 1-230 ◽

Cited By ~ 5

Author(s):

Steve Goodacre ◽

Kimberley Horspool ◽

Neil Shephard ◽

Daniel Pollard ◽

Beverley J Hunt ◽

...

Keyword(s):

Diagnostic Imaging ◽

Clinical Features ◽

Thrombin Generation ◽

Case Control Study ◽

Multivariable Analysis ◽

Decision Rules ◽

Clinical Decision ◽

Postpartum Women ◽

Control Study ◽

D Dimer

Background Pulmonary embolism (PE) is a leading cause of death in pregnancy and post partum, but the symptoms of PE are common in normal pregnancy. Simple diagnostic tests are needed to select women for diagnostic imaging. Objective To estimate the accuracy, effectiveness and cost-effectiveness of clinical features, decision rules and biomarkers for selecting pregnant or postpartum women with a suspected PE for imaging. Design An expert consensus study to develop new clinical decision rules, a case–control study of women with a diagnosed PE or a suspected PE, a biomarker study of women with a suspected PE or diagnosed deep-vein thrombosis (DVT) and decision-analysis modelling. Setting Emergency departments and consultant-led maternity units. Participants Pregnant/postpartum women with a diagnosed PE from any hospital reporting to the UK Obstetric Surveillance System research platform and pregnant/postpartum women with a suspected PE or diagnosed DVT at 11 prospectively recruiting sites. Interventions Clinical features, decision rules and biomarkers. Main outcome measures Sensitivity, specificity, area under receiver operating characteristic (AUROC) curve, quality-adjusted life-years (QALYs) and health-care costs. Results The primary analysis involved 181 women with PE and 259 women without PE in the case–control study and 18 women with DVT, 18 with PE and 247 women without either in the biomarker study. Most clinical features showed no association with PE. The AUROC curves for the clinical decision rules were as follows: primary consensus, 0.626; sensitive consensus, 0.620; specific consensus, 0.589; PE rule-out criteria, 0.621; simplified Geneva score, 0.579; Wells’s PE criteria (permissive), 0.577; and Wells’s PE criteria (strict), 0.732. The sensitivities and specificities of the D-dimer measurement were 88.4% and 8.8%, respectively, using a standard threshold, and 69.8% and 32.8%, respectively, using a pregnancy-specific threshold. Previous venous thromboembolism, long-haul travel, multiple pregnancy, oxygen saturation, recent surgery, temperature and PE-related chest radiograph abnormality were predictors of PE on multivariable analysis. We were unable to derive a rule through multivariable analysis or recursive partitioning with adequate accuracy. The AUROC curves for the biomarkers were as follows: activated partial thromboplastin time – 0.669, B-type natriuretic peptide – 0.549, C-reactive protein – 0.542, Clauss fibrinogen – 0.589, enzyme-linked immunosorbent assay D-dimer – 0.668, Innovance D-dimer (Siemens Healthcare Diagnostics Products GmbH, distributed by Sysmex UK Ltd, Milton Keynes, UK) – 0.651, mid-regional pro-atrial natriuretic peptide (MRproANP) – 0.524, prothrombin fragment 1 + 2 – 0.562, plasmin-antiplasmin – 0.639, Prothombin time – 0.613, thrombin generation lag time – 0.702, thrombin generation endogenous potential – 0.559, thrombin generation peak – 0.596, thrombin generation time to peak – 0.655, tissue factor – 0.531 and troponin – 0.597. The repeat analysis excluding women who had received anticoagulation was limited by the small number of women with PE (n = 4). The health economic analysis showed that a strategy of scanning all women with a suspected PE accrued more QALYs and incurred fewer costs than any selective strategy based on a clinical decision rule and was therefore the dominant strategy. Limitations The findings apply specifically to the diagnostic assessment of women with a suspected PE in secondary care. Conclusions Clinical features, decision rules and biomarkers do not accurately, effectively or cost-effectively select pregnant or postpartum women with a suspected PE for diagnostic imaging. Future work New diagnostic technologies need to be developed to detect PE in pregnancy. Trial registration Current Controlled Trials ISRCTN21245595. Funding details This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 22, No. 47. See the NIHR Journals Library website for further project information.

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Decision Rules and Risk Analysis

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.625.26 ◽

2014 ◽

Vol 625 ◽

pp. 26-33 ◽

Cited By ~ 1

Author(s):

Michael Krystek

Keyword(s):

Measurement Uncertainty ◽

Decision Rules ◽

Uncertainty Budget ◽

Economic Consequences ◽

Manufactured Products ◽

Acceptance Limits ◽

The Stability ◽

The Relationship ◽

Product Specification

Measurement uncertainty has important economic consequences for calibration and inspection activities and is often taken as an indication of the quality of a test laboratory. Smaller uncertainty values are generally of higher value. In industry decision rules employed in accepting and rejecting products are based on the measurement uncertainty budget of the related characteristics of the products. Conformity assessment based on the product specification and the measurement evaluation is an important part of the industrial quality assurance of manufactured products and for the stability of production processes. The aim of this paper is to describe the relationship between the conformance zone and the acceptance zone and to address the problem of determining acceptance limits that define the boundaries of the acceptance zone.

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