Three Graphic Representations to Aid Bayesian Inference

1988 ◽  
Vol 27 (03) ◽  
pp. 125-132 ◽  
Author(s):  
W. G. Cole
Keyword(s):  
Laboratory Test ◽  
Signal Detection ◽  
Bayesian Reasoning ◽  
False Negatives ◽  
Probability Maps ◽  
Test Parameters ◽  
Graphic Representations ◽  
Laboratory Results ◽  
Formal Properties ◽  
Sensitivity Specificity

SummaryVisual representation may help physicians and patients interpret laboratory results, for example by aiding Bayesian reasoning. This paper is concerned with the psychological and formal properties of such visual representations. One popular way to present laboratory results is via signal detection curves. These curves represent many parameters of a laboratory test including parameters, such as distribution variance, that are not typically known. Such curves can be seriously misleading.Two alternative representations are suggested. Probability maps represent only the three laboratory test parameters most likely to be known: sensitivity, specificity and prevalence, and thus avoid the problems of the richer signal detection curves. Probability maps, however, do not remind the user of why there are false positives and false negatives nor of the nature of the criterion for positivity. Detection bars, a third type of representation, are a compromise between signal detection curves and probability maps.

scholarly journals The Impact of Increasing Prevalence, False Omissions, and Diagnostic Uncertainty on Coronavirus Disease 2019 (COVID-19) Test Performance

2021 ◽  
Author(s):  
Gerald J. Kost
Keyword(s):  
Test Performance ◽  
Influenza A ◽  
Geometric Mean ◽  
False Positives ◽  
Test Quality ◽  
False Negatives ◽  
Predictive Values ◽  
Sensitivity Specificity ◽  
Tier 3 ◽  
The Impact

ABSTRACT Context. Coronavirus disease 2019 (COVID-19) test performance depends on predictive values in settings of increasing disease prevalence. Geospatially distributed diagnostics with minimal uncertainty facilitate efficient point-of-need strategies. Objectives. To use original mathematics to interpret COVID-19 test metrics; assess Food and Drug Administration Emergency Use Authorizations and Health Canada targets; compare predictive values for multiplex, antigen, polymerase chain reaction kit, point-of-care antibody, and home tests; enhance test performance; and improve decision-making. Design. PubMed/newsprint generated articles documenting prevalence. Mathematica and open access software helped perform recursive calculations, graph multivariate relationships, and visualize performance by comparing predictive value geometric mean-squared patterns. Results. Tiered sensitivity/specificity comprise: T1) 90%, 95%; T2) 95%, 97.5%; and T3) 100%, ≥99%. Tier 1 false negatives exceed true negatives at >90.5% prevalence; false positives exceeded true positives at <5.3% prevalence. High sensitivity/specificity tests reduce false negatives and false positives yielding superior predictive values. Recursive testing improves predictive values. Visual logistics facilitate test comparisons. Antigen test quality falls off as prevalence increases. Multiplex severe acute respiratory syndrome (SARS)-CoV-2)*Influenza A/B*Respiratory-Syncytial Virus (RSV) testing performs reasonably well compared to Tier 3. Tier 3 performance with a Tier 2 confidence band lower limit will generate excellent performance and reliability. Conclusions. The overriding principle is select the best combined performance and reliability pattern for the prevalence bracket. Some public health professionals recommend repetitive testing to compensate for low sensitivity. More logically, improved COVID-19 assays with less uncertainty conserve resources. Multiplex differentiation of COVID-19 from Influenza A/B-RSV represents an effective strategy if seasonal flu surges next year.

Herbal Remedies: Effects on Clinical Laboratory Tests

2006 ◽  
Vol 130 (4) ◽  
pp. 521-528 ◽  
Author(s):  
Amitava Dasgupta ◽  
David W. Bernard
Keyword(s):  
Chinese Medicine ◽  
Laboratory Test ◽  
Alternative Medicine ◽  
Clinical Laboratory ◽  
Herbal Remedies ◽  
Test Results ◽  
Abnormal Laboratory ◽  
St John's Wort ◽  
Laboratory Test Results ◽  
Laboratory Results

AbstractContext.—Complementary and alternative medicine (herbal medicines) can affect laboratory test results by several mechanisms.Objective.—In this review, published reports on effects of herbal remedies on abnormal laboratory test results are summarized and commented on.Data Sources.—All published reports between 1980 and 2005 with the key words herbal remedies or alternative medicine and clinical laboratory test, clinical chemistry test, or drug-herb interaction were searched through Medline. The authors' own publications were also included. Important results were then synthesized.Data Synthesis.—Falsely elevated or falsely lowered digoxin levels may be encountered in a patient taking digoxin and the Chinese medicine Chan Su or Dan Shen, owing to direct interference of a component of Chinese medicine with the antibody used in an immunoassay. St John's wort, a popular herbal antidepressant, increases clearance of many drugs, and abnormally low cyclosporine, digoxin, theophylline, or protease inhibitor concentrations may be observed in a patient taking any of these drugs in combination with St John's wort. Abnormal laboratory results may also be encountered owing to altered pathophysiology. Kava-kava, chaparral, and germander cause liver toxicity, and elevated alanine aminotransferase, aspartate aminotransferase, and bilirubin concentrations may be observed in a healthy individual taking such herbal products. An herbal product may be contaminated with a Western drug, and an unexpected drug level (such as phenytoin in a patient who never took phenytoin but took a Chinese herb) may confuse the laboratory staff and the clinician.Conclusions.—Use of alternative medicines may significantly alter laboratory results, and communication among pathologists, clinical laboratory scientists, and physicians providing care to the patient is important in interpreting these results.

Test of a Noninvasive Instrument for Measuring Hemoglobin Concentration

1989 ◽  
Vol 5 (4) ◽  
pp. 659-667 ◽  
Author(s):  
Constanza I. Sanchez-Carrillo ◽  
Teresita de Jesus Ramirez-Sanchez ◽  
Marcela Zambrana-Castañeda- ◽  
Beatrice J. Selwyn
Keyword(s):  
Decision Making ◽  
Negative Predictive Value ◽  
Predictive Value ◽  
False Negative ◽  
Hemoglobin Concentration ◽  
Reliability Test ◽  
Intraobserver Variability ◽  
Hemoglobin Content ◽  
False Negatives ◽  
Sensitivity Specificity

A colorimetric instrument for the noninvasive quantification of hemoglobin, designed using color shades resembling those observed in the conjunctiva, was tested. The instrument's colors are contrasted against the color of the conjunctiva to measure hemoglobin content. Sensitivity, specificity, negative predictive value, and false-negative value were estimated to test the instrument's accuracy; kappa coefficients were used to estimate inter- and intraobserver variability. Physician field evaluations of conjunctiva color for the screening of anemia, reported in the literature, have had sensitivities and specificities as high as 70%. Readings with the instrument demonstrated a 63% sensitivity, 72% specificity, and 38% false negatives for screening hemoglobin values of less than or equal to 13 g/dl. The interobserver kappa coefficients for three pairs of readers were good to excellent for the same hemoglobin screening value. Statistically significant differences were noted, however, between observers during the reliability test. The instrument can be used by unskilled personnel to improve their decision-making about whom to send for futher care or for supplementation with iron.

scholarly journals Accuracy and Quality Assessment of EUS-FNA: A Single-Center Large Cohort of Biopsies

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Benjamin Ephraim Bluen ◽  
Jesse Lachter ◽  
Iyad Khamaysi ◽  
Yassin Kamal ◽  
Leonid Malkin ◽  
...  
Keyword(s):  
Quality Control ◽  
Lymph Nodes ◽  
Diagnostic Accuracy ◽  
Learning Curve ◽  
Monitoring And Evaluation ◽  
Definitive Diagnosis ◽  
Single Center ◽  
False Negatives ◽  
Biopsy Site ◽  
Sensitivity Specificity

Introduction. Thorough quality control (QC) study with systemic monitoring and evaluation is crucial to optimizing the effectiveness of EUS-FNA. Methods. Retrospective analysis was composed of investigating consecutive patient files that underwent EUS-FNA. QC specifically focused on diagnostic accuracy, impacts on preexisting diagnoses, and case management. Results. 268 patient files were evaluated. EUS-FNA cytology helped establish accurate diagnoses in 92.54% (248/268) of patients. Sensitivity, specificity, PPV, NPV, and accuracy were 83%, 100%, 100%, 91.6%, and 94%, respectively. The most common biopsy site was the pancreas (68%). The most accurate location for EUS-FNA was the esophagus, 13/13 (100%), followed by the pancreas (89.6%). EUS-FNA was least informative for abdominal lymph nodes (70.5%). After FNA and followup, eight false negatives for tumors were found (3%), while 7.5% of samples still lacked a definitive diagnosis. Discussion. QC suggests that the diagnostic accuracy of EUS-FNA might be improved further by (1) taking more FNA passes from suspected lesions, (2) optimizing needle selection (3) having an experienced echo-endoscopist available during the learning curve, and (4) having a cytologist present during the procedure. QC also identified remediable reporting errors. In conclusion, QC study is valuable in identifying weaknesses and thereby augmenting the effectiveness of EUS-FNA.

scholarly journals On the True Number of COVID-19 Infections: Effect of Sensitivity, Specificity and Number of Tests on Prevalence Ratio Estimation

2020 ◽  
Vol 17 (15) ◽  
pp. 5328
Author(s):  
Eitan Altman ◽  
Izza Mounir ◽  
Fatim-Zahra Najid ◽  
Samir M. Perlaza
Keyword(s):  
Sensitivity And Specificity ◽  
Estimation Error ◽  
Prevalence Ratio ◽  
Test Results ◽  
Estimation Errors ◽  
Public Health Policies ◽  
True Number ◽  
Test Parameters ◽  
Sensitivity Specificity ◽  
Work First

In this paper, a formula for estimating the prevalence ratio of a disease in a population that is tested with imperfect tests is given. The formula is in terms of the fraction of positive test results and test parameters, i.e., probability of true positives (sensitivity) and the probability of true negatives (specificity). The motivation of this work arises in the context of the COVID-19 pandemic in which estimating the number of infected individuals depends on the sensitivity and specificity of the tests. In this context, it is shown that approximating the prevalence ratio by the ratio between the number of positive tests and the total number of tested individuals leads to dramatically high estimation errors, and thus, unadapted public health policies. The relevance of estimating the prevalence ratio using the formula presented in this work is that precision increases with the number of tests. Two conclusions are drawn from this work. First, in order to ensure that a reliable estimation is achieved with a finite number of tests, testing campaigns must be implemented with tests for which the sum of the sensitivity and the specificity is sufficiently different than one. Second, the key parameter for reducing the estimation error is the number of tests. For a large number of tests, as long as the sum of the sensitivity and specificity is different than one, the exact values of these parameters have very little impact on the estimation error.

Preoperative Assessment of Myometrial Invasion in Endometrial Cancer by 3D Ultrasound and Diffusion-Weighted Magnetic Resonance Imaging: A Comparative Study

2016 ◽  
Vol 26 (6) ◽  
pp. 1105-1110 ◽  
Author(s):  
Adriano Rodríguez-Trujillo ◽  
María José Martínez-Serrano ◽  
Sergio Martínez-Román ◽  
Cristina Martí ◽  
Laura Buñesch ◽  
...  
Keyword(s):  
Endometrial Cancer ◽  
Early Stage ◽  
Myometrial Invasion ◽  
3D Ultrasound ◽  
Resonance Imaging ◽  
False Negatives ◽  
Weighted Magnetic Resonance Imaging ◽  
Sensitivity Specificity ◽  
And Diffusion ◽  
Early Stage Endometrial Cancer

ObjectiveThe prognosis of endometrial cancer depends on the correct surgical staging. In early stages, 18% to 30% rate of positive lymph nodes is reported with a myometrial invasion of 50% or more. According to this, patients with International Federation of Gynecology and Obstetrics stage Ib would benefit from staging lymphadenectomy. Therefore, it is important to classify these patients preoperatively to plan the surgery. In the recent years, 3-dimensional (3D) ultrasound and diffusion-weighted magnetic resonance imaging (DW-MRI) have been incorporated in the preoperative management of these patients. The aim of this study was to assess the usefulness of 3D ultrasound and DW-MRI as predictor of myometrial invasion in endometrial cancer.Material and MethodsWe retrospectively compared the assessment of myometrial invasion by 3D ultrasound and DW-MRI with final pathologic evaluation on hysterectomy specimens, in 98 patients diagnosed of early-stage endometrial cancer, who underwent surgery at the Hospital Clinic of Barcelona between 2012 and 2015.ResultsEvaluation of the depth of myometrial invasion with 3D ultrasound had a sensitivity, specificity, and accuracy of 77%, 83% and 81%, respectively. Evaluation of the depth of myometrial invasion with DW-MRI had a sensitivity, specificity, and accuracy of 69%, 86%, and 81%, respectively. Association of both techniques improved all the values, showing a sensitivity, specificity, and accuracy of 87%, 93%, and 91%, respectively. In both 3D ultrasound and DW-MRI, the presence of leiomyomas was the first detectable cause of false negative (3% and 4%, respectively) and false-positive (3% and 1%, respectively).ConclusionsWe conclude that the implementation of the 2 studies in early-stage endometrial cancer provides low false-negatives and false-positives rates. In cases of patients with leiomyomas, adenomiosis, or intrauterine fluid collection, definitive evaluation of myometrial invasion could be better deferred to intraoperative biopsy in an attempt to reduce false-negatives and false-positives rates.

scholarly journals Use of the14C Breath Test in the Treatment ofHelicobacter pylori

1995 ◽  
Vol 9 (4) ◽  
pp. 191-194 ◽  
Author(s):  
AJ Rae ◽  
A Belzberg ◽  
IGM Cleator ◽  
M Caglar
Keyword(s):  
Helicobacter Pylori ◽  
Gold Standard ◽  
Breath Test ◽  
Acute Inflammation ◽  
Eradication Therapy ◽  
False Negatives ◽  
Breath Testing ◽  
Amoxicillin Trihydrate ◽  
One Year ◽  
Sensitivity Specificity

Fifty-two patients with gastric disorders referred to the same physician over the course of one year were endoscoped, biopsied and given a14C breath test to identifyHelicobacter pylori. Sensitivity, specificity and accuracy of the14C breath test were found to be 83%, 89% and 87%, respectively, when taking biopsy results as the `gold standard'. These figures rose to 85%, 93% and 89%, respectively, when the first five cases were not included, representing a ‘learning curve’ associated with the development of cut-off levels for the breath test. In five cases, persons were biopsied and given a breath test at least one month later, making 10 comparisons possible. Biopsy and breath test corresponded in nine of 10 comparisons (90%). In two of four false negatives (14C breath test negative but biopsy positive) only scant numbers of helicobacter organisms were found. In one of three false positives (14C breath test positive but biopsy negative) acute inflammation of the duodenal biopsied material was detected. Also, double eradication therapy (omeprazole 20 mg bid and amoxicillin trihydrate 1000 mg bid), administered in all three false positive cases, was followed by14C breath testing six weeks later, which indicated normal scores or absence of the organism.

scholarly journals Unit conversions between LOINC codes

2017 ◽  
Vol 25 (2) ◽  
pp. 192-196 ◽  
Author(s):  
Ronald G Hauser ◽  
Douglas B Quine ◽  
Alex Ryder ◽  
Sheldon Campbell
Keyword(s):  
Laboratory Test ◽  
Data Aggregation ◽  
Controlled Vocabulary ◽  
Test Results ◽  
Computational Process ◽  
Clinical Tests ◽  
Laboratory Test Results ◽  
Immunodeficiency Virus ◽  
Laboratory Results ◽  
Sodium Magnesium

Abstract Logical Observation Identifiers Names and Codes (LOINC) is the most widely used controlled vocabulary to identify laboratory tests. A given laboratory test can often be reported in more than 1 unit of measure (eg, grams or moles), and LOINC defines unique codes for each unit. Consequently, an identical laboratory test performed by 2 different clinical laboratories may have different LOINC codes. The absence of unit conversions between compatible LOINC codes impedes data aggregation and analysis of laboratory results. To develop such conversions, a computational process was developed to review the LOINC standard for potential conversions, and multiple expert reviewers oversaw and finalized the conversion list. In all, 285 bidirectional conversions were identified, including conversions for routine clinical tests such as sodium, magnesium, and human immunodeficiency virus (HIV). Unit conversions were applied to the aggregation of laboratory test results to demonstrate their usefulness. Diverse informatics projects may benefit from the ability to interconvert compatible results.

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