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What-Is-Case-Series.Pdf Asploro Journal of Biomedical and Clinical Case Reports Editorial What is case series? Abdel-Hady El-Gilany* *Corresponding author: Abdel-Hady El-Gilany Address: Professor of Public Health & Preventive Medicine, Faculty of Medicine, Mansoura University, Egypt. Received date: 19 August 2018; Accepted date: 29 August 2018; Published date: 2 September 2018 Citation: El-Gilany AH, ―What is case series?‖, Asp Biomed Clin Case Rep, vol.1, no.1: 10-15, 2018. Copyright © 2018 El-Gilany AH. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract This is the second part of a series on case reports and case series studies. It will help junior researchers to comprehend what is the case series/exposure series as a type of research. It highlights the definition, types, importance, limitations, and differences between case series and exposure series. Examples of important historical case series that were instrumental in the early identification of health problems will be mentioned. A special editorial will be devoted to consecutive controlled case series (CCCS)/ self-controlled case series (SCCS) as an important research method. Keywords: Case series, exposure series, definition, types, importance, limitations. Introduction describing the potential effectiveness of new Case series (also known as clinical series) interventions, for describing the effectiveness of represents one of the most basic types of study interventions on unusual diagnoses, and for designs, in which researchers describe the describing unusual responses (either good or experience of a small group of people. It bad) to interventions. Case series can be presents a detailed account of the clinical conducted retrospectively or prospectively. The experience of individual study subjects and can primary distinction between case reports/series evaluate large numbers of individuals and and the single-subject experiment is that the summarize the data using descriptive statistical researcher does not manipulate the intervention measures [1]. A case series is a variation of a in a case report/series but merely single case report in which the author describes describes/documents what happened during the several cases and their relation to one another normal course of the intervention. Despite and to the existing body of literature. limitations, case series can often have a significant impact on the current practice of Definition medicine and they are often used to put together The Dictionary of Epidemiology defined a case definitions of new diseases and to define case series as ―a collection of patients with future areas of clinical study [3]. However, no common characteristics used to describe some causal inferences should be made from case clinical, pathophysiological or operational series regarding the efficacy of the investigated aspects of a disease, treatment or diagnostic treatment [4]. A case series samples patients with procedures‖[2]. Case series is an observational, both a specific outcome and a specific exposure, descriptive research design. It is most useful for or samples patients with a specific outcome and Manuscript no: ASJBCCR-1-10-15 Volume: 1 Issue: 1 10 Short name: ASJBCCR Citation: El-Gilany AH, “What is case series?”, Asp Biomed Clin Case Rep, vol.1, no.1: 10-15, 2018 Key Words: Case series, exposure series, definition, types, importance, limitations. Editorial includes patients regardless of whether they risk can be calculated. Selection is based only have specific exposures [5]. on a specific outcome, and data are collected on previous exposures. Types of case series There are many classifications for case *Clinical vs. population-based series: [10, series. 11, 12] -Clinical case series: usually a coherent and *Informal vs. formal case series: [6, 7] consecutive set of cases of a disease recruited -Informal case series: cases are selected for from one or more center by one or more specific reasons: best case, worse case, researcher. It is a clinic-based register of cases significant variations. The format of this kind of that are analyzed together to learn about the case series is: introduction; case 1, case 2, disease. They are of value in epidemiology for case 3, etc. (each case is presented like a short studying symptoms and signs, creating case case description); discussion (cases will be definitions as well as clinical education, audit, and compared to one another, related cases to the research. current literature, implications of the findings, teaching points and what changes in clinical -Population-based case series: when a clinical practice this might engender). case-series is limited and complete for a defined geographical area for which the population is -Formal case series: include all cases of a known, it is a population-based case-series specific type, or with specific selection criteria, consisting of a population register of cases. It is presented more like a cohort study than a single usually compiled for administrative and legal case report and its format is introduction reasons. methods, results, and discussion/conclusions. By knowing the past history of these patients, *Consecutive vs. non-consecutive case including examination of past medical records, series: [5, 8] and by continuing to observe them to death, -Consecutive case series: includes all eligible health professionals can build up a picture of the patients identified by the researchers during the natural history of a disease in clinical case series. study period. The patients are treated in the Population case-series is a systematic extension order in which they are identified. of this series but which includes additional cases, Consecutiveness increases the quality of e.g. those dying without being seen by the clinicians. It adds breadth to the understanding of the case series. the spectrum and natural history of the disease. Information on the population permits calculation -Non-consecutive case series: includes of rates, understanding the distribution of disease some, but not all, of the eligible patients in populations and to the study of variations over identified by the researchers during the study time, between places and by population period. characteristics. Epidemiologically the most important case-series are registers of serious *Exposure or outcome-based sampling: diseases or deaths, and of health service [5, 9] utilization, e.g. hospital admissions. -Exposure-based sampling: include all patients treated and have specific outcomes or Design of case series adverse events. Sampling is based on both a Case series research is a descriptive study to specific outcome and presence of a specific present patients in their natural clinical setting. exposure. The case series can be retrospective or prospective and may be consecutive or non- -Outcome-based sampling: includes patients consecutive depending on whether all cases with the specific outcome regardless of presenting to the reporting authors over a period exposure. Thus neither absolute risk nor relative were included, or only a selection [13]. Manuscript no: ASJBCCR-1-10-15 Volume: 1 Issue: 1 11 Short name: ASJBCCR Citation: El-Gilany AH, “What is case series?”, Asp Biomed Clin Case Rep, vol.1, no.1: 10-15, 2018 Key Words: Case series, exposure series, definition, types, importance, limitations. Editorial • Who: The characteristics of the population The study question should be focused (person). and appropriate. The question should not be Noting the socio-demographic characteristics whether the investigated treatment is more of a series of cases, as well as the temporal and effective or safer than another treatment. It spatial distributions can sometimes provide a should list the study population, the intervention clue to risk factors and hence help generate a and the primary outcome [4]. hypothesis. This can be tested subsequently with more elaborate analytic studies. The setting: Select a suitable observation • The opportunity to collect additional data from period and identify cases with events in this medical records (possibly by electronic Data period. It may be tempting to include patients linkage) or the person directly. seen over a large period of time to increase sample size. However, the use of a short A detailed description of the intervention inclusion period minimizes known and unknown and the co-intervention should be stated. This changes over time in co-interventions, prognosis, will ensure repeatability of the study by other and even in the intervention under study [4, 14]. investigators. It is very important to thoroughly describe co-interventions. Additionally, Number of cases: there is no thumb rule or a indications for the studied treatment should be magic number. The general number of cases explained. This will primarily determine the reported in a case series range from 20 to 50, but consistency of the patient group [4]. may vary from as few as 2 or 3 to as many as more than 100 [10] or even thousands [6]. The blinding of outcome assessors is ideal in every kind of research design and can be N.B. Case-only analyses are sometimes implemented quite usefully in case-series performed in genetic epidemiology to investigate studies (e.g., by having some investigators the association between an exposure and a collect data only on an outcome and others genotype [15]. collect data only on patient characteristics). This prevents the investigators’
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