China 
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Clinical Trials in NEC Research
Published in David J. Hackam, Necrotizing Enterocolitis, 2021
Cheryl Battersby, Chris Gale, Neena Modi
The lack of an agreed-upon evidence-based case definition or reliable diagnostic test introduces the risk of ascertainment bias, particularly in un-blinded trials. In around two-thirds of infants treated for presumed NEC, the diagnosis is based on clinical assessment without tissue confirmation. The presenting features of NEC are nonspecific, sharing clinical, radiological, and laboratory features with diagnoses such as septic ileus, feed intolerance, spontaneous intestinal perforation, and intestinal dysmotility syndromes (12). The radiological features of pneumatosis and portal venous gas, widely considered diagnostic of NEC, occur late in the disease and are subject to interobserver variability (13–15). Even when the bowel is visualized at surgery, the diagnosis can be controversial. Until a validated biomarker is available for clinical use, there is need for consistent application of a definition that discriminates well between infants with and without NEC. Unfortunately, most NEC case definitions have not been validated against a gold standard (16–21). The most widely used, Bell criteria, was devised by a surgeon in the 1970s to guide surgical management after the diagnosis was made and was not intended as a case definition (22, 23). We used a large population dataset to develop a gestational age–specific case definition (24), acknowledging that a continuing challenge is the absence of a reliable diagnostic biomarker to provide a “gold standard” (25).
Pregnant Trauma Patients
Published in Stephen M. Cohn, Matthew O. Dolich, Kenji Inaba, Acute Care Surgery and Trauma, 2016
Trauma is a leading cause of non-obstetrical maternal mortality. Knowledge of anatomic and physiologic alterations in pregnancy, correct evaluation of both mother and fetus, and careful considerations of conditions specific to pregnancy are essential to ensure the best outcome. Although the literature on trauma in pregnancy is quite extensive, it is characterized by several limitations. The majority of studies are retrospective, and even prospective works do not have a matching control group. Many studies relied on hospitalized patients rise a concern of ascertainment bias, as only severe trauma cases were identified (Table 27.2). Multi-institutional retrospective data collection following prospective phone follow-up may shed more light on the existing controversies.
Epidemiological Approaches to Studying Cancer I
Published in Peter G. Shields, Cancer Risk Assessment, 2005
Ascertainment bias: Error due to systematic failure to represent equally all classes of cases or persons supposed to be represented in a sample. Ascertainment bias may arise from the nature of the sources from which the persons come (63).
Update on Optic Neuritis: An International View
Published in Neuro-Ophthalmology, 2022
Simon J. Hickman, Axel Petzold
The presentations and visual outcomes from studies around the world for first episodes of different types of optic neuritis in predominantly adult populations are shown in Table 5–7. The reason for looking at outcomes from first episodes of optic neuritis was to try and make the results of each study more easily comparable. The studies varied, though in terms of age of patients, gender balance and treatment, but also how the data were presented. We tried to present comparable data between the studies, although we have not performed statistical comparisons due to the apparent variability in the data. This was particularly the case for presenting and outcome visual acuities. We presented the proportion of subjects, where recorded, with good and poor visual acuities, expressed as a Snellen decimal (for ease of comparison), at presentation and at last follow-up. In most cases, it was not clear how case ascertainment occurred and since these were hospital-based studies there may have been some case ascertainment bias with more severe cases being referred to the hospitals where the studies were reported from, potentially leading to apparently poor outcomes in some of the case series.
Lower urinary tract symptoms (LUTS) are not associated with an increased risk of prostate cancer in men 50–69 years with PSA ≥3 ng/ml
Published in Scandinavian Journal of Urology, 2020
Jan Chandra Engel, Thorgerdur Palsdottir, Markus Aly, Lars Egevad, Henrik Grönberg, Martin Eklund, Tobias Nordström
Ørsted et al. [5] on the other hand presented a very large observational study of more than 3 million men in Denmark showing that men with LUTS had an increased risk of prostate cancer [HR 2.2 (95% CI: 2.13–2.31)] over a follow-up period of 27 years. A Norwegian study of about 30,000 also showed increased risk of detecting prostate cancer in men with LUTS with HR of 4.6 (2.23–9.54) in men with severe LUTS [11]. One of the main limitations in these studies arguing for a positive association between LUTS and cancer is the ascertainment bias that inevitably occurs in observational studies. Given the association between PSA, prostate volume and urinary symptoms together with the increased testing among men with such symptoms, it is possible that more prostate cancer will be detected in men with urinary symptoms compared to the control groups. Stockholm3 employed a prospective screen-by-invitation design with a pre-defined PSA cutoff for biopsy referrals. Followingly, the problem with ascertainment bias is markedly mitigated.
The overlap between epilepsy and Alzheimer’s disease and the consequences for treatment
Published in Expert Review of Neurotherapeutics, 2019
Graham Powell, Besa Ziso, AJ Larner
It was initially thought that generalized seizures, presumably secondarily generalized from a partial seizure focus, predominated in AD [16], and that complex partial seizures may also occur but might be under-recognized in the context of progressive dementia [26]. These conclusions may simply have been a reflection of ascertainment bias. More subtle changes may easily be overlooked. Occasional cases of transient epileptic amnesia (TEA) have been described in the early stages of AD [27,28] and suggested as a contributory factor to wandering behavior exhibited by some AD patients [29]. At the other end of the epilepsy spectrum, status epilepticus, of complex partial [30] or non-convulsive [31] type, has been described on occasion in association with AD. A recent study using a proforma to elicit symptoms suggestive of epilepsy in patients with AD and mild cognitive impairment (MCI) identified a broad range of seizure-related phenomena, including altered responsiveness, automatisms (oral, pharyngeal), auras (olfactory, gustatory), arrest of speech or behaviour, focal motor seizures, sensory phenomena including hallucinations, and amnesia on waking (typical of TEA). Most seizures were subtle and non-convulsive and hence easily missed [32].