Methodological issues in diagnostic studies

Sarkhy, Ahmed Al

doi:10.4103/1319-3767.77253

Cited by 5 publications

(6 citation statements)

References 5 publications

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“…Imaging studies often use surgery, pathological findings or the clinical follow-up as standard [21]. The example in reference [48] shows that the validity of the entire study is questioned if a reference standard is applied that does not conform to the usual standard [49]. Specifically, Dehdashti et al…”

Section: Gold Standard Versus Reference Standardmentioning

confidence: 99%

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Challenges in planning and conducting diagnostic studies with molecular biomarkers

Ziegler

König

Schulz‐Knappe

2013

Dtsch med Wochenschr

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Section: Gold Standard Versus Reference Standardmentioning

confidence: 99%

“…Instead, the current reference standard is monitoring the pH value in the esophagus. In combination with further methodological issues, the author of a letter to the editor [49] stated that "..., this study has several critical methodological flaws, …".…”

Section: Gold Standard Versus Reference Standardmentioning

confidence: 99%

Challenges in planning and conducting diagnostic studies with molecular biomarkers

Ziegler

König

Schulz‐Knappe

2013

Dtsch med Wochenschr

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“…In bildgebenden Studien werden häufig Operation, pathologische Befunde oder die klinische Nachbeobachtung als Standard gewählt [21]. Wird ein Referenzstandard verwendet, der nicht dem üblichen Standard entspricht, wird, wie das Beispiel [48] zeigt, die Validität der ganzen Studie in Frage gestellt [49]. In ihrer Arbeit haben Dehdashti und Kollegen [48] Bariumbrei als Referenzstandard zur Diagnose der Refluxerkrankung verwendet, obwohl die Nordamerikanische Gesellschaft für päd-iatrische Gastroenterologie, Hepatologie und Ernährung dieses nicht unterstützt.…”

Section: Goldstandard Versus Referenzstandardunclassified

“…Der gegenwärtige Referenzstandard ist hier das Monitorieren des pH-Werts in der Speiseröhre. Zusammen mit anderen methodischen Schwächen hat der Autor des Leserbriefs [49] geschrieben: "…, this study has several critical methodological flaws, …"…”

Section: Goldstandard Versus Referenzstandardunclassified

Herausforderungen an die Planung und Durchführung von Diagnosestudien mit molekularen Biomarkern

Ziegler

König

Schulz‐Knappe

2013

Dtsch med Wochenschr

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Biomarkers are of increasing importance for personalized medicine in many areas of application, such as diagnosis, prognosis, or the selection of targeted therapies. In many molecular biomarker studies, intensity values are obtained from large scale ‑omics experiments. These intensity values, such as protein concentrations, are often compared between at least two groups of subjects to determine the diagnostic ability of the molecular biomarker. Various prospective or retrospective study designs are available for molecular biomarker studies, and the biomarker used may be univariate or may even consist in a multimarker rule. In this work, several challenges are discussed for the planning and conduct of biomarker studies. The phases of diagnostic biomarker studies are closely related to levels of evidence in diagnosis, and they are therefore discussed upfront. Different study designs for molecular biomarker studies are discussed, and they primarily differ in the way subjects are selected. Using two systematic reviews from the literature, common sources of bias of molecular diagnostic studies are illustrated. The extreme selection of patients and controls and verification bias are specifically discussed. The pre-analytical and technical variability of biomarker measurements is usually expressed in terms of the coefficient of variation, and is of great importance for subsequent validation studies for molecular biomarkers. It is finally shown that the required sample size for biomarker validation quadratically increases with the coefficient of variation, and the effect is illustrated using real data from different laboratory technologies.

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“…Namely, some studies did not compare US findings to a gold standard test such as the pH metry/ impedance study -in fact some of these studies compare it to barium swallow which is neither sensitive nor specific for GER/GERD diagnosis. In some of these studies, the GER/GERD diagnosis had variable denominators for diagnosis which were therefore not comparable [13]. Others tried to measure an age-standardized abdominal esophagus length in children without taking into consideration the effect of the weight/ height of the children, which could be a potential confounding factor on these measurements and probably therefore would affect its clinical application [14].…”

mentioning

confidence: 99%

Assessment of GERD: Ultrasound

Sarkhy

2017

Esophageal and Gastric Disorders in Infancy and Childhood

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Ultrasound (US) or sonography has been utilized for many years in different fields of diagnostic imaging, including GERD diagnosis mainly due to pragmatic reasons: low cost, wide availability, and relative noninvasiveness [1][2][3][4].US study allows for direct, real-time visualization of the gastroesophageal junction (GEJ) and of the retrograde movement of reflux events. In addition, it can detect anatomical defects such as hiatus hernia and indirectly measure the lower esophageal sphincter (LES) length. Color Doppler ultrasound was also added to the standard US study which has been reported to increase its sensitivity in detecting GER events [5][6][7][8]. Furthermore, recent studies started to use endoscopic US in the measurement of the esophageal wall thickness to assess esophageal inflammation secondary to GERD; however, this is still an evolving technique [9,10]. Using specific criteria, Tomita et al. conducted a study to correlate the abdominal US findings with endoscopy findings in adult patients with erosive GERD (n = 37) and nonerosive GERD (n = 24) compared to a control group without GERD (n = 32). All of the participants had upper gastrointestinal endoscopy. The US operator was not aware of the endoscopy findings. GERD was diagnosed when two or more of these items were positive: (i) lower esophageal thickness (> or = 5 mm), (ii) abnormal architecture of the esophageal wall, and (iii) the presence of reflux. The thickness in erosive GERD was reported to be significantly greater than that in nonerosive reflux disease (NERD) patients and controls. Sensitivity, specificity, and accuracy of abdominal US diagnosis for erosive GERD and NERD (control participants worked as a reference group) were 84.6 %, 25 %, 91.1 % and 91.1 %, 89.4 %, and 63.8 %, respectively [11].Though US is a cheap and noninvasive diagnostic tool, it does have several limitations in GERD diagnosis. These include its inability to depict the intrathoracic esophagus which limits the study to a short segment of the distal esophagus; another limitation is that it provides only a snap shot picture of the fluid movement across a short period of time. However, the major limitation is that it does not provide any information about the nature of the refluxate (acidic or not) and it does not correlate well with the reflux index of acid reflux as measured by pH monitoring [8,12]. Jang et al. conducted a study where contrast color Doppler US (CDUS) and 24-h esophageal pH monitoring were performed in 54 children (2 months to 10 years). The authors demonstrated that CDUS had a high sensitivity (95.5 %) for diagnosing the presence of GER but a very low specificity (11.0 %), with a positive predictive value of 84.3 % and a negative A. Sarkhy, MBBS, MHSc, FAAP, FRCP

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Methodological issues in diagnostic studies

Cited by 5 publications

References 5 publications

Challenges in planning and conducting diagnostic studies with molecular biomarkers

Challenges in planning and conducting diagnostic studies with molecular biomarkers

Herausforderungen an die Planung und Durchführung von Diagnosestudien mit molekularen Biomarkern

Assessment of GERD: Ultrasound

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