scholarly journals Estimating Prevalence Using an Imperfect Test

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Peter J. Diggle
Keyword(s):  
Confidence Intervals ◽  
Diagnostic Test ◽  
Random Sample ◽  
Sensitivity And Specificity ◽  
Bayesian Method ◽  
Standard Estimate ◽  
Credible Intervals ◽  
Positive Results ◽  
Imperfect Test

The standard estimate of prevalence is the proportion of positive results obtained from the application of a diagnostic test to a random sample of individuals drawn from the population of interest. When the diagnostic test is imperfect, this estimate is biased. We give simple formulae, previously described by Greenland (1996) for correcting the bias and for calculating confidence intervals for the prevalence when the sensitivity and specificity of the test are known. We suggest a Bayesian method for constructing credible intervals for the prevalence when sensitivity and specificity are unknown. We provide R code to implement the method.

Exact confidence limits for prevalence of a disease with an imperfect diagnostic test

2010 ◽  
Vol 138 (11) ◽  
pp. 1674-1678 ◽  
Author(s):  
J. REICZIGEL ◽  
J. FÖLDI ◽  
L. ÓZSVÁRI
Keyword(s):  
Confidence Intervals ◽  
Diagnostic Test ◽  
Sensitivity And Specificity ◽  
Simulation Study ◽  
Confidence Level ◽  
Asymptotic Methods ◽  
Real Life ◽  
Disease Status ◽  
Confidence Limits ◽  
Extensive Simulation

SUMMARYEstimation of prevalence of disease, including construction of confidence intervals, is essential in surveys for screening as well as in monitoring disease status. In most analyses of survey data it is implicitly assumed that the diagnostic test has a sensitivity and specificity of 100%. However, this assumption is invalid in most cases. Furthermore, asymptotic methods using the normal distribution as an approximation of the true sampling distribution may not preserve the desired nominal confidence level. Here we proposed exact two-sided confidence intervals for the prevalence of disease, taking into account sensitivity and specificity of the diagnostic test. We illustrated the advantage of the methods with results of an extensive simulation study and real-life examples.

scholarly journals Evaluation of Bias in Diagnostic-Test Sensitivity and Specificity Estimates Computed by Discrepant Analysis

1998 ◽  
Vol 36 (2) ◽  
pp. 375-381 ◽  
Author(s):  
Timothy A. Green ◽  
Carolyn M. Black ◽  
Robert E. Johnson
Keyword(s):  
Cell Culture ◽  
Nucleic Acid ◽  
Diagnostic Test ◽  
Sensitivity And Specificity ◽  
Nucleic Acid Amplification ◽  
Reference Test ◽  
Test Sensitivity ◽  
Test Specificity ◽  
Positive Results

When a new diagnostic test is potentially more sensitive than the reference test used to classify persons as infected or uninfected, a substantial number of specimens from infected persons may be reference-test negative but new-test positive. Discrepant analysis involves the performance of one or more additional tests with these specimens, reclassification as infected those persons for whom the new-test-positive results are confirmed, and recalculation of the estimates of new-test sensitivity and specificity by using the revised classification. This approach has been criticized because of the bias introduced by the selective use of confirmation testing. Under conditions appropriate for evaluating a nucleic acid amplification (NAA) test for Chlamydia trachomatis infection with cell culture as the reference test, we compared the bias in estimates based on the discrepant-analysis classification of persons as infected or uninfected with that in estimates based on the culture classification. We concluded that the bias in estimates of NAA-test specificity based on discrepant analysis is small and generally less than that in estimates based on culture. However, the accuracy of discrepant-analysis-based estimates of NAA-test sensitivity depends critically on whether culture specificity is equal to or is slightly less than 100%, and it is affected by competing biases that are not fully taken into account by discrepant analysis.

A Note on Confidence Intervals and Model Specification

Marketing ZFP ◽  
2019 ◽  
Vol 41 (4) ◽  
pp. 33-42
Author(s):  
Thomas Otter
Keyword(s):  
Confidence Intervals ◽  
Generalized Linear Model ◽  
Statistical Information ◽  
Regression Coefficients ◽  
Model Specification ◽  
Model Parameters ◽  
Exploratory Research ◽  
Empirical Calibration ◽  
Credible Intervals ◽  
Model Structures

Empirical research in marketing often is, at least in parts, exploratory. The goal of exploratory research, by definition, extends beyond the empirical calibration of parameters in well established models and includes the empirical assessment of different model specifications. In this context researchers often rely on the statistical information about parameters in a given model to learn about likely model structures. An example is the search for the 'true' set of covariates in a regression model based on confidence intervals of regression coefficients. The purpose of this paper is to illustrate and compare different measures of statistical information about model parameters in the context of a generalized linear model: classical confidence intervals, bootstrapped confidence intervals, and Bayesian posterior credible intervals from a model that adapts its dimensionality as a function of the information in the data. I find that inference from the adaptive Bayesian model dominates that based on classical and bootstrapped intervals in a given model.

scholarly journals Diagnostic Performance of Ankle-Brachial Pressure Index in Lower Extremity Arterial Disease

2021 ◽  
Vol 07 (03) ◽  
pp. e132-e137
Author(s):  
Mohammed Alagha ◽  
Thomas M. Aherne ◽  
Ahmed Hassanin ◽  
Adeel S. Zafar ◽  
Doireann P. Joyce ◽  
...  
Keyword(s):  
Lower Extremity ◽  
Sensitivity And Specificity ◽  
False Negative ◽  
Arterial Disease ◽  
Initial Assessment ◽  
Reference Standard ◽  
Lower Extremity Arterial Disease ◽  
Negative Results ◽  
Positive Results ◽  
Arterial Imaging

Abstract Introduction Ankle-brachial pressure indices (ABIs) continue to form the basis of diagnostics for lower extremity arterial disease (LEAD). However, there remains a paucity of data to support its accuracy. This study aims to evaluate its diagnostic sensitivity and specificity using established arterial-imaging modalities as a benchmark. Methods In this retrospective study, a regional, prospectively maintained, vascular laboratory database was interrogated to identify referred patients with arterial disease who underwent concomitant assessment with ABI and lower limb arterial duplex ultrasound (DUS). Duplex acted as the reference standard. Those who had peripheral computed tomography angiogram (CTA) within 3 months of initial assessment were included in a subgroup analysis to correlate ABI with CTA. The primary end point was the sensitivity and specificity of ABI compared with DUS as the reference standard. Results Concomitant assessment was performed in 438 limbs (250 patients) over a 27-month period. The ABI was normal (0.9 to 1.4) in 196 limbs (44.9%) and abnormal in the remaining 241 limbs (55.1%). False-positive results occurred in 83 out of 241 limbs (34.4%), and false-negative results occurred in 54 limbs out of 196 (27.5%). True-positive results were 158 out of 241 limbs (65.6%), whereas true-negative results were 142 out of 196 limbs (72.4%). ABI using DUS as a benchmark identified a sensitivity for peripheral artery disease of 72.3% and a specificity of 69.3%. Concomitant CTA imaging was available in 200 limbs. The sensitivity and specificity of ABI correlated with CTA were 65.5 and 68.8%, respectively. Conclusion ABIs have a moderate predictive value in the diagnosis of LEAD. Normal range outcomes cannot be taken to infer the absence of LEAD and, as such, further arterial imaging in the form of DUS or angiography should be strongly considered in those with suspected underlying disease requiring intervention. Further noninvasive tests such as exercise studies or pulse volume waveforms should be considered, if diagnostic uncertainty exists, in those requiring nonoperative intervention and risk factor control.

scholarly journals A new highly sensitive and specific overnight combined screening and diagnostic test for primary aldosteronism

2016 ◽  
Vol 175 (1) ◽  
pp. 21-28 ◽  
Author(s):  
Vaios Tsiavos ◽  
Athina Markou ◽  
Labrini Papanastasiou ◽  
Theodora Kounadi ◽  
Ioannis I Androulakis ◽  
...  
Keyword(s):  
Diagnostic Test ◽  
Sensitivity And Specificity ◽  
Primary Aldosteronism ◽  
Low Cost ◽  
Confirmatory Test ◽  
Outpatient Basis ◽  
Endocrine Hypertension ◽  
Serum Aldosterone ◽  
Highly Sensitive ◽  
Aldosterone To Renin Ratio

Context Primary aldosteronism (PA) is the most common cause of endocrine hypertension that is diagnosed following a two-step process: an initial screening test, based on the serum aldosterone-to-renin ratio (ARR), followed by a relatively laborious and time-consuming confirmatory test to document autonomous aldosterone (ALD) secretion. Objective The aim of this study is to develop a simple overnight test for the early and definite diagnosis of PA. Patients and methods Totally, 148 hypertensive patients underwent a fludrocortisone–dexamethasone suppression test (FDST) and the new overnight diagnostic test (DCVT) using pharmaceutical RAAS (renin–angiotensin–aldosterone system) blockade with dexamethasone, captopril and valsartan. Results Of the 148 patients, 45 were diagnosed as having PA and they all normalized their elevated blood pressure (BP) after administration of spironolactone or eplerenone. The remaining 103 patients were considered as having essential hypertension and served as controls. Using ROC analysis, the estimated sensitivity and specificity were 91 and 100%, respectively, for the post-FDST ARR, whereas 98% and 89% and 100% and 82% for the post-DCVT ARR and post-DCVT ALD, respectively, with selected cutoffs of 0.32ng/dL/μU/mL and 3ng/dL respectively. However, considering these cutoffs simultaneously, the estimated sensitivity and specificity were 98 and 100% respectively. Applying these cutoffs, the diagnosis of PA was confirmed in 44 (98%) of the 45 patients who were considered to have the disease. Conclusions In this study, a highly sensitive and specific, low-cost, rapid, safe, and easy-to-perform diagnostic test (DCVT) for PA is described, which could be utilized on an outpatient basis potentially substituting conventional laborious testing.

Role of MR venography in the evaluation of deep venous thrombosis

1997 ◽  
Vol 38 (5) ◽  
pp. 907-912 ◽  
Author(s):  
C. Catalano ◽  
P. Pavone ◽  
A. Laghi ◽  
A. Scipioni ◽  
F. Fanelli ◽  
...  
Keyword(s):  
Venous Thrombosis ◽  
Deep Venous Thrombosis ◽  
Sensitivity And Specificity ◽  
Filling Defect ◽  
Clinical Suspicion ◽  
Mr Venography ◽  
Diagnostic Modalities ◽  
Positive Results ◽  
Intraluminal Filling Defect

Purpose: MR venography has been recommended for the evaluation of deep venous thrombosis. The purpose of our study was to determine the role of MR venography, in particular at the level of the pelvis where other diagnostic modalities show major limitations. Materials and Methods: Forty-three patients with clinical suspicion of deep venous thrombosis were examined by means of pelvic MR venography. In all cases, a 2D-TOF sequence was used with cranial arterial presaturation. In selected cases, i.e. when a small intraluminal filling defect was present, a cine-PC sequence was used in addition in order to exclude the presence of a pulsatility artifact as causing the filling defect. In all cases, contrast venography was also performed and considered to be the standard of reference. Results: MR venography showed 26 patients to be positive for deep venous thrombosis at the pelvic level. These positive results were correct in 25 cases. The analysis of the results provided values of sensitivity and specificity of respectively 100% and 94%, with an overall accuracy of 97.6%. Conclusion: Our results indicate that MR can provide highly accurate images, similar to those of contrast venography, in a noninvasive fashion. It is particularly useful in the pelvic region where the limitations of other imaging modalities are more evident.

scholarly journals Observed Differences in Diagnostic Test Accuracy between Patient Subgroups: Is It Real or Due to Reference Standard Misclassification?

2007 ◽  
Vol 53 (10) ◽  
pp. 1725-1729 ◽  
Author(s):  
Corné Biesheuvel ◽  
Les Irwig ◽  
Patrick Bossuyt
Keyword(s):  
Clinical Practice ◽  
Diagnostic Test ◽  
Sensitivity And Specificity ◽  
Diagnostic Test Accuracy ◽  
Test Accuracy ◽  
Reference Standard ◽  
Target Condition ◽  
Test Sensitivity ◽  
The Past ◽  
Patient Subgroups

Abstract Before a new test is introduced in clinical practice, its accuracy should be assessed. In the past decade, researchers have put an increased emphasis on exploring differences in test sensitivity and specificity between patient subgroups. If the reference standard is imperfect and the prevalence of the target condition differs among subgroups, apparent differences in test sensitivity and specificity between subgroups may be caused by reference standard misclassification. We provide guidance on how to determine whether observed differences may be explained by reference standard misclassification. Such misclassification may be ascertained by examining how the apparent sensitivity and specificity change with the prevalence of the target condition in the subgroups.

scholarly journals Utility of Glycated Hemoglobin in Diagnosing Type 2 Diabetes Mellitus: A Community-Based Study

2010 ◽  
Vol 95 (6) ◽  
pp. 2832-2835 ◽  
Author(s):  
Padala Ravi Kumar ◽  
Anil Bhansali ◽  
Muthuswamy Ravikiran ◽  
Shobhit Bhansali ◽  
Pinaki Dutta ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Diagnostic Test ◽  
Sensitivity And Specificity ◽  
Predictive Value ◽  
Hba1c Level ◽  
Glycated Hemoglobin ◽  
World Health ◽  
Oral Glucose ◽  
Community Based ◽  
Cut Point

Abstract Context: Although glycated hemoglobin (HbA1c) has recently been incorporated as a diagnostic test by the American Diabetes Association, its validity needs to be established in Asian Indians in a community setting. Objective: The objective of the study was to assess the validity of HbA1c as a screening and diagnostic test in individuals with newly detected diabetes mellitus. Design and Setting: Community based randomized cross sectional study in urban Chandigarh, a city in north India, from April 2008 to August 2009. Subjects: Subjects included 1972 subjects aged 20 yr or older. Intervention: Intervention included an oral glucose tolerance test and glycated hemoglobin in all the subjects. Main Outcome Measures: Utility of HbA1c as a diagnostic method in newly detected diabetes mellitus subjects was evaluated. Results: Using World Health Organization criteria for diagnosis of diabetes mellitus, 134 (6.7%) had newly detected diabetes mellitus, 192 (9.7%) known diabetes mellitus, 329 (16.6%) prediabetes, and 1317 (69.4%) were normal of 1972 people screened. Using only the ADA criteria, 38% people were underdiagnosed. An HbA1c level of 6.1% had an optimal sensitivity and specificity of 81% for diagnosing diabetes. A HbA1c level of 6.5% (±2 sd) and 7% (±2.7 sd) had sensitivity and specificity of 65 and 88% and 42 and 92%, respectively, with corresponding positive predictive value and negative predictive value of 75.2 and 96.5% and 90.4and 94.4%, respectively, for diagnosis of newly detected diabetes mellitus. Conclusion: A HbA1c cut point of 6.1% has an optimal sensitivity and specificity of 81% and can be used as a screening test, and a cut point of 6.5% has optimal specificity of 88% for diagnosis of diabetes.

COMPARISON OF FOURTH GENERATION ELISA AND RAPID DIAGNOSTIC TEST FOR DIAGNOSIS OF HEPATITIS C VIRUS(HCV) INFECTION IN A TERTIARY CARE HOSPITAL.

2021 ◽  
pp. 15-17
Author(s):  
Stuti Kansra Arora ◽  
Mala Chhabra ◽  
Anuradha Anuradha ◽  
Arvind Achra ◽  
Nandini Duggal
Keyword(s):  
Diagnostic Test ◽  
Rapid Diagnostic Test ◽  
Sensitivity And Specificity ◽  
Treatment Initiation ◽  
Tertiary Care ◽  
Hcv Infection ◽  
Fourth Generation ◽  
World Population ◽  
Test Results ◽  
Blood Samples

Introduction:Hepatitis C virus (HCV) infection has emerged as one of the major global health challenge affecting about 2 - 3% of the world population. Epidemiological studies have shown that HCV infection is a major risk factor for development of Acute hepatitis,chronic liver disease,cirrhosis and Hepatocellular carcinoma (HCC).Early diagnosis of HCV is important to link hepatitis testing to care and treatment initiation. Aim:To compare sensitivity and specificity of rapid diagnostic test (RDT) with fourth generation ELISA Material and Method: This study was conducted in the Department of Microbiology at Atal Bihari Vajpayee Institute of Medical Sciences (formerly Post Graduate Institute of Medical Education and Research) and Dr Ram Manohar Lohia Hospital from January 2018 to December 2018.Blood samples of patients suspected with hepatitis were tested using ELISA and rapid diagnostic test Results: In our study 26378 blood samples were tested for HCV,using fourth generation ELISA.Of these,581(2.20%) samples were found to be positive by ELISA.These HCV positive samples along with equal number of ELISA negative samples were tested by rapid diagnostic test. Sensitivity and specificity of the rapid diagnostic test was found to be 72.98 % and 100% respectively. Discussion:Rapid diagnostic test can be used during emergency hours but their results must be followed by ELISA test results in a tertiary care hospital.Reporting of false negative results should be minimized for rapid linkage to treatment initiation and to avoid silent transmission of infection.

Sign in / Sign up

Export Citation Format

Share Document