Clinical Epidemiology

Author(s):  
Scott C. Litin ◽  
John B. Bundrick

Diagnostic tests are tools that either increase or decrease the likelihood of disease. The sensitivity, specificity, and predictive values of normal and abnormal test results can be calculated with even a limited amount of information. Some physicians prefer interpreting diagnostic test results by using the likelihood ratio. This ratio takes properties of a diagnostic test (sensitivity and specificity) and makes them more helpful in clinical decision making. It helps the clinician determine the probability of disease in a specific patient after a diagnostic test has been performed.

1993 ◽  
Vol 7 (2) ◽  
pp. 66-69 ◽  
Author(s):  
C.W. Douglass

The presentations at this conference will discuss new technologies and rapid scientific developments that have resulted in new diagnostic tests for periodontal disease, musculoskeletal imaging, temporomandibular joint dysfunctions, and incipient coronal and root dental caries. However, for many of these claims, there has been insufficient scientific support regarding the sensitivity and specificity of the tests, or their ability to predict the percent of cases in which the disease or condition progresses to the next state of development. Research is needed that will yield the basic diagnostic parameters of new diagnostic tests, i.e., their accuracy, precision, sensitivity, specificity, positive predictive value, and negative predictive value. The purpose and methods for calculating each of these measures are described in this paper. Five questions are then presented that will need to be addressed in future research regarding new diagnostic tests: (1) Does the scientific theory of the test fit with our current body of knowledge? (2) Have the efficacy parameters of the test been reliably determined? (3) How does the test affect clinical decision-making? (4) Does using the test improve the patient's health? and (5) Is the added expense of the test justified by increased effectiveness or by avoiding other health expenditures?


2021 ◽  
Author(s):  
Alfred Kipyegon Keter ◽  
Lutgarde Lynen ◽  
Alastair van Heerden ◽  
Els Goetghebeur ◽  
Bart K.M. Jacobs

Abstract Background Lack of a perfect reference standard for pulmonary tuberculosis (PTB) diagnosis complicates assessment of accuracy of new diagnostic tests. Alternative strategies such as discrepant resolution and use of composite reference standards may lead to incorrect inferences on disease prevalence and diagnostic test sensitivity and specificity. Latent class analysis (LCA), a statistical method for analyzing diagnostic test results in the absence of a gold standard, allows correct estimation under strict assumptions. The model assumes that the diagnostic tests are independent conditional on the true disease status and that the diagnostic test sensitivity and specificity remain constant across subpopulations. These assumptions are violated when a factor such as severe comorbidity affects the prevalence and/or alters the diagnostic test performance. We aim to provide guidance on correct estimation of the prevalence and diagnostic test accuracy based on LCA when a known factor induces dependence among the diagnostic tests. If unaccounted for, this dependence may lead to misleading inferences. Methods Through likelihood evaluation and simulation we examined implications of likely model violations on estimation of prevalence, sensitivity and specificity among passive case-finding presumptive PTB patients with or without HIV. We generated independent results for five diagnostic tests conditional on PTB and HIV. We performed Bayesian LCA, separately for five and three diagnostic tests using four working models with or without constant PTB prevalence and diagnostic test accuracy across HIV subpopulations. Results In evaluating three diagnostic tests, the models accounting for heterogeneity in diagnostic accuracy produced consistent estimates while the models ignoring it produced biased estimates. The model ignoring heterogeneity in PTB prevalence is less problematic. When evaluating five diagnostic tests, the models were robust to violation of the assumptions. Conclusions Well-chosen covariate-specific adaptations of the model can avoid bias implied by recognized heterogeneity in PTB patient populations generating otherwise dependent test results in LCA.


2015 ◽  
Vol 54 (03) ◽  
pp. 283-287 ◽  
Author(s):  
L. Herich ◽  
W. Lehmacher ◽  
M. Hellmich

SummaryObjective: To present a geometric ruler to determine predictive values of binary diagnostic test results from prevalence, sensitivity and specificity without calculation.Methods: On logarithmic scale the relationships between pre-/post-test odds and the likelihood ratio as well as sensitivity, specificity and the likelihood ratio appear as simple linear (additive) equations.Results: Each of these additive equations can be solved geometrically in form of a ruler with three scales. By amalgamation we devise a novel non-electronic tool which omits the intermediate step of likelihood ratio determination.Conclusions: We propose a simple geometric method to aid in interpretation of diagnostic test results for both practical and educational purposes.


2000 ◽  
Vol 4 (1) ◽  
pp. 19-25 ◽  
Author(s):  
Michael Binder ◽  
Stephan Dreiseitl

Background: Dermatologists need to interpret an increasing number of research studies and diagnostic tests. Understanding the techniques for interpreting test results and making decisions based upon those tests represent important tools for decision making for both clinicians and researchers. Objective: This article focuses briefly on the key parameters of diagnostic tests: sensitivity, specificity, prevalence, predictive values, likelihood ratios, and the concept of receiver-operating-characteristic (ROC) curves. A simple example is presented in a step-by-step manner. Conclusion: The principles of interpreting test results are easy to learn and applicable in daily clinical routine. Therefore, dermatologists should be familiar with the concepts outlined in this paper.


CJEM ◽  
2002 ◽  
Vol 4 (05) ◽  
pp. 348-354 ◽  
Author(s):  
Andrew Worster ◽  
Grant Innes ◽  
Riyad B. Abu-Laban

ABSTRACT: Emergency physicians use diagnostic tests extensively, and the ability to order and interpret test results appropriately is a critical skill. An understanding of sensitivity, specificity, predictive values and likelihood ratios, as well as an awareness of the importance of pre-test probability, is essential. The purpose of this article is to explain, in a straightforward and clinically applicable manner, the core concepts related to diagnostic testing.


2021 ◽  
Vol 34 (2) ◽  
pp. e100453
Author(s):  
Hongyue Wang ◽  
Bokai Wang ◽  
Xunan Zhang ◽  
Changyong Feng

Diagnostic tests are usually based on some quantitative biomarkers. Two key parameters used to characterise the quality of a test are test sensitivity and specificity. Predictive values of the disease status based on test results are also of interest in medical research and public health management. In this paper, we study the relations among sensitivity, specificity and predictive values of the test. The core concept is risk function, which is assumed to be an increasing function of the biomarker. Our results show that test sensitivity and specificity change in opposite directions. The positive predictive value and the sensitivity also change in opposite directions. Likewise, the negative predictive value and the specificity change in opposite directions.


2003 ◽  
Vol 1 (2) ◽  
pp. 198-207
Author(s):  
H. Mabel Preloran ◽  
Silvia Balzano

This paper explores the emotional world of a recent Mexican immigrant who lives in Los Angeles and is awaiting the results of the amniocentesis she has ambivalently agreed to. She is 45 years old and has given birth to two children with severe disabilities and two who are apparently normal. We focus our analysis on the woman's reactions and feelings during the nine days she spends waiting for the test results. We show that the standard prenatal genetic clinical protocol aimed at providing medical education and requiring professional neutrality and emotional detachment left the woman feeling rejected and subsequently unwilling to seek information or support from her clinicians. We find that while the intent of a protocol of neutrality is to enable patients to make informed decisions without feeling pressure from clinicians, some women want greater emotional engagement. We argue that professional neutrality can inhibit patient-clinician communication, hamper medical education, and ultimately detract from patients' ability to make informed medical choices. / El presente artículo explora el mundo emocional de Rocío, una inmigrante mexicana, quien se encuentra esperando los resultados de una amniocentesis que aceptó hacerse, a pesar de las dudas sobre la credibilidad y utilidad de la misma. Rocío, de 45 años, tenía ya otros hijos, dos con anormalidades severas y dos aparentemente sanos. Centramos nuestro análisis en los sentimientos y reacciones durante los nueve días que transcurren mientras espera el diagnóstico. En este trabajo mostramos cómo la forma de presentar la información médica puede llegar a entorpecer la toma de decisión de un paciente. El protocolo genético tiene por meta proveer información médica manteniendo una cierta distancia profesional y emocional. Estas condiciones hacen que, en nuestro estudio de caso, la paciente se sienta rechazada y sin deseos de acercarse al personal médico, ya sea en busca de apoyo emocional o información que aclararía sus dudas. Creemos que, mientras el objetivo de la neutralidad profesional es asegurar que el paciente decida con los conocimientos adecuados y, a la vez, sin sentirse presionado, algunas mujeres preferirían un mayor acercamiento emocional por parte del personal médico cuando deben decidir sobre pruebas o tratamientos. Creemos que la neutralidad profesional puede llegar a inhibir la comunicación médico-paciente, dificultar la comprensión de la información y, por último, obstaculizar la habilidad de tomar decisiones informadas por parte de los pacientes.


Author(s):  
Mary Kathryn Bohn ◽  
Siobhan Wilson ◽  
Alexandra Hall ◽  
Khosrow Adeli

Abstract Objectives The Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) has developed an extensive database of reference intervals (RIs) for several biomarkers on various analytical systems. In this study, pediatric RIs were verified for key immunoassays on the Abbott Alinity system based on the analysis of healthy children samples and comparison to comprehensive RIs previously established for Abbott ARCHITECT assays. Methods Analytical performance of Alinity immunoassays was first assessed. Subsequently, 100 serum samples from healthy children recruited with informed consent were analyzed for 16 Alinity immunoassays. The percentage of test results falling within published CALIPER ARCHITECT reference and confidence limits was determined. If ≥ 90% of test results fell within the confidence limits, they were considered verified based on CLSI guidelines. If <90% of test results fell within the confidence limits, additional samples were analyzed and new Alinity RIs were established. Results Of the 16 immunoassays assessed, 13 met the criteria for verification with test results from ≥ 90% of healthy serum samples falling within the published ARCHITECT confidence limits. New CALIPER RIs were established for free thyroxine and prolactin on the Alinity system. Estradiol required special considerations in early life. Conclusions Our data demonstrate excellent concordance between ARCHITECT and Alinity immunoassays, as well as the robustness of previously established CALIPER RIs for most immunoassays, eliminating the need for de novo RI studies for most parameters. Availability of pediatric RIs for immunoassays on the Alinity system will assist clinical laboratories using this new platform and contribute to improved clinical decision-making.


Author(s):  
Sameer Ahmed

Background: The initial evaluation of patient with multiple trauma is a challenging task. FAST (focussed assessment with sonography in trauma) provides a viable alternative to computed tomography in blunt abdominal trauma patient. The aim of this study was to find the accuracy and utility of FAST in clinical decision making, as well as limitations.Methods: A total of 100 patients with blunt abdominal trauma who underwent FAST examination were included. Positive scan was defined as the presence of free intraperitoneal fluid. The sonographic scoring for operating room triage in trauma (SSORTT Score) was calculated using cumulative sum of ultrasound score, systolic blood pressure, and pulse rate. FAST findings were compared with computed tomography findings and in operated cases compared with surgical findings & clinical outcome.Results: We determined SSORTT score in all 100 cases. In our study, the sensitivity, specificity, positive and negative predictive values for FAST in identifying intraabdominal injuries were 93.9%, 94.2%, 87.5%, and 97.2%. In our study we found out that patients with a SSORTT score of 2 and above had a high likelihood of requiring a therapeutic laparotomy.Conclusions: In our study we found that FAST is a rapid, reproducible, portable and non-invasive bedside test, and can be performed at the same time as resuscitation. Ultrasound is limited mainly by its low sensitivity in directly demonstrating solid organs injuries.


Author(s):  
Tokponnon F ◽  
◽  
Osse R ◽  
Houessou C ◽  
Akogbeto M ◽  
...  

Parasitological diagnosis is a fundamental element in the adequate management of the disease. In the last decade, there has been a resurgence of interest in the development of malaria Rapid Diagnostic Test (RDT) kits. This is the case with SD Bioline Malaria Ag Pf, which searches for HRP2 antigen by immunochromatography. The objective of this study is to compare the results of RDT SD Bioline Malaria Ag Pf in use with the results of Thick Gout (TG) in the biological diagnosis of malaria. This was a cross-sectional, descriptive and evaluative study carried out at the Hôpital d’Instruction des Armées-Center Hospitalier et Universitaire de Parakou and at the Boko zone hospital from April 20 to July 30, 2015. Patient identification, we used the non-probabilistic method and the convenience choice technique. The study involved 503 patients. The results of this study showed a good performance of the RDT SD Bioline Malaria Ag Pf. Among the 503 patients, 199 or 39.6% were positive for the RDT against 180 or 35.8% positive for the Thick Gout (TG). Sensitivity, specificity, positive and negative predictive values of the test compared to the thick film were respectively (91.7%, 89.5%, 82.9, 95) and the Kappa coefficient of 0.88 testifies a good match. False positive cases are noted in patients on treatment and even after recovery due to the persistence of the HRP2 antigen in the blood. However, it constitutes an interesting alternative to the management of malaria. At the end of this study, we suggest continuing the use of RDTs in health centers where microscopy is absent and/or reinforcing microscopy, and to strengthen staff training in the management of malaria cases.


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