Study design: what's in a name?

The name of the study should properly reflect the actual conduct and analysis of the study. This short paper provides guidance on how to properly name the study design. The first distinction is between a trial (intervention given to patients to study its effect) and an observational study. For observational studies, it should further be decided whether it is cross-sectional or whether follow-up time is taken into account (cohort or case-control study). The distinction prospective-retrospective has two disadvantages: prospective is often seen as marker of higher quality, which is not necessarily true; there is no unifying definition that makes a proper distinction between retrospective and prospective possible.

Observational studies and the difficult quest for causality: lessons from vaccine effectiveness and impact studies.

Although randomized placebo-controlled trials (RCT) are critical to establish efficacy of vaccines at the time of licensure, important remaining questions about vaccine effectiveness (VE)-used here to include individual-level measures and population-wide impact of vaccine programmes-can only be answered once the vaccine is in use, from observational studies. However, such studies are inherently at risk for bias. Using a causal framework and illustrating with examples, we review newer approaches to detecting and avoiding confounding and selection bias in three major classes of observational study design: cohort, case-control and ecological studies. Studies of influenza VE, especially in seniors, are an excellent demonstration of the challenges of detecting and reducing such bias, and so we use influenza VE as a running example. We take a fresh look at the time-trend studies often dismissed as 'ecological'. Such designs are the only observational study design that can measure the overall effect of a vaccination programme [indirect (herd) as well as direct effects], and are in fact already an important part of the evidence base for several vaccines currently in use. Despite the great strides towards more robust observational study designs, challenges lie ahead for evaluating best practices for achieving robust unbiased results from observational studies. This is critical for evaluation of national and global vaccine programme effectiveness.

[Observational studies in the era of evidence based medicine: short review on their relevance, taxonomy and designs]. / Estudos Observacionais na Era da Medicina Baseada na Evidência: Breve Revisão Sobre a Sua Relevância, Taxonomia e Desenhos.

In this review of the literature, we distinguish between experimental and observational studies, highlighting the importance that the later have gained in the era of evidence-based medicine. We further analyze the value of observational studies in light of experimental studies. We present a taxonomy for observational studies based on units of observation and measurement (cross-sectional or longitudinal). We distinguish between descriptive studies and analytical studies. Then, and given its specificity, we define and present a classification for ecological studies. We define and consider the advantages and disadvantages of cross-sectional, case control and cohort studies. We analyze the strength of the evidence given by each study design. We finished by examining what should guide the choice of a study design.

Nesta revisão narrativa da literatura, distinguimos entre estudos experimentais e estudos observacionais, realçando a importância que estes últimos têm vindo a ganhar na era da medicina baseada na evidência cujo gold standard são os estudos experimentais. Apresentamos uma taxonomia para os estudos observacionais que se baseia nas unidades de observação e na medição (transversal ou longitudinal). Distinguimos entre estudos descritivos e estudos analíticos. Em seguida, e dada a sua especificidade, definimos e apresentamos uma classificação própria para os estudos ecológicos. Definimos e tecemos considerações sobre as vantagens e desvantagens dos estudos transversais, de caso controlo e de coorte. Analisamos a força da evidência de cada desenho de estudo. Terminamos concluindo sobre o que deve orientar a escolha do desenho de estudo.

Reporting observational studies of the use of information technology in the clinical consultation. A position statement from the IMIA Primary Health Care Informatics Working Group (IMIA PCI WG).

OBJECTIVES: To develop a classification system to improve the reporting of observational studies of the use of information technology (IT) in clinical consultations. METHODS: Literature review, workshops, and development of a position statement. We grouped the important aspects for consistent reporting into a "faceted classification"; the components relevant to a particular study to be used independently. RESULTS: The eight facets of our classification are: (1) Theoretical and methodological approach: e.g. dramaturgical, cognitive; (2) DATA COLLECTION: Type and method of observation; (3) Room layout and environment: How this affects interaction between clinician, patient and computer. (4) Initiation and Interaction: Who starts the consultation, and how the participants interact; (5) Information and knowledge utilisation: What sources of information or decision support are used or provided; (6) Timing and type of consultation variables: Standard descriptors that can be used to allow comparison of duration and description of continuous activities (e.g. speech, eye contact) and episodic ones, such as prescribing; (7) Post-consultation impact measures: Satisfaction surveys and health economic assessment based on the perceived quality of the clinician-patient interaction; and (8) Data capture, storage, and export formats: How to archive and curate data to facilitate further analysis. CONCLUSIONS: Adoption of this classification should make it easier to interpret research findings and facilitate the synthesis of evidence across studies. Those engaged in IT-consultation research shouldconsider adopting this reporting guide.

Aproximación a una taxonomía de los diseños observacionales / A Taxonomy for observational designs

El trabajo plantea identificar los criterios que permiten diferenciar y definir los distintos diseños observacionales. Se proponen cuatro criterios básicos: 1) criterio Temporal, relativo al momento en el que son recogidos los indicadores de conducta, dimensión que fluctúa entre dos polos: a) Diacrónico cuando se relacionan indicadores recogidos en distintos momentos temporales, corresponde a la perspectiva de seguimiento y b) Sincrónico, si estos indicadores corresponden a la misma sesión de observación, sería una perspectiva puntual. 2) criterio del Número de Sujetos observados, dimensión que varía entre a) la perspectiva idiográfica centrada en un solo sujeto, y b) la perspectiva nomotética cuando es observada una pluralidad de individuos. 3) criterio de Relaciones entre las Unidades, con tres dimensiones: a) relaciones de Independencia, asociaciones entre las unidades, b) relaciones de Dependencia, establecimiento de causalidad entre las unidades, y c) relaciones de Interdependencia. 4) criterio de Nivel de Respuesta, vinculado a la existencia en la investigación de una o más modalidades de conducta diferenciadas según su contenido y producción. Estos criterios básicos deben de ser complementados con una serie de criterios secundarios relacionados con: 1) los instrumentos de observación empleados: codificación binaria, sistemas de categorías, formatos de campo, escalas de apreciación, etc. 2) las técnicas de muestreo: a) Intersesional, selección de momentos de comienzo y fin de las sesiones, b) Intrasesional, selección de sujetos que centran la atención del observador. 3) las técnicas de registro que especifiquen las propiedades de las categorías a registrar y el momento en que se realiza: a) registro continuo, b) en puntos de tiempo y c) de intervalos. La segunda vertiente consiste en la ubicación en este marco de una relación lo más exhaustiva posible de las investigaciones observacionales dirigidas, o en las que se ha colaborado, desde el ámbito universitario. Se presenta un resumen global del objeto de estudio, las problemáticas abordadas, el contexto de aplicación, etc (AU)

Four basic criteria are proposed in order to classify the observational designs. 1) Time criterion, relative to the moment in which the behavior is registered. This criterion would oscillate between two poles: synchronous and diachronic. 2) Number of subjects observed, varying from one to several subjects. 3) Relationships between the units, with three dimensions: Independence, dependence, and interdependence. 4) Level of the answer, related to the existence of one or more behavior modalities. These basic criteria most be complemented with other secondary criteria, such as: a) instruments used in the observation, b) sample techniques, and c) behavior register techniques, such as continuous or interval registers. Finally, the use of these criteria are discussed, and the applicability problems analyzed (AU)