F
Filomena Pereira-Maxwell in Medical Statistics, 2018
A clinical trial or epidemiological study in which information is collected by following study participants over a period of time, thus allowing temporal relationships to be investigated. The terms prospective and longitudinal are sometimes used as synonymous with follow-up study, but the former simply indicates that a study is conducted looking forward in terms of data collection and occurrence of events, even when there is no follow-up in the usual sense of the expression (e.g. prospective nested case-control study). On the other hand, a retrospective cohort study is a longitudinal study, although study participants are not actually followed up as all exposures and events of interest have already taken place. Follow-up studies are often concerned with estimating the incidence over time of some occurrence or disease, or the average ‘time to event’ and/or probability of survival.
Cancer Epidemiology
Trevor F. Cox in Medical Statistics for Cancer Studies, 2022
Cohort studies are forward looking, where individuals are selected to be members of one or more cohorts, the selection being based on risk exposure and demographic variables. The cohort(s) are followed up for a certain period of time, with data collected on cancer outcomes and other variables. Data is often collected at various timepoints during the course of the study. This is a prospective cohort study which may take years to complete. Another type of cohort study is an historical cohort study or sometimes called a retrospective cohort study, where the data are obtained from historical records, appropriate individuals being selected for the cohort(s), again based on risk and demographic variables. Their records are then traced forward to see how the cancer outcome variables performed up to a particular time point. It is as if the researcher travels back in time and then conducts a prospective cohort study, eventually arriving back to the present.
Understanding Studies of Resistant Organisms: Focus on Epidemiologic Methods
Robert C. Owens, Lautenbach Ebbing in Antimicrobial Resistance, 2007
In a cohort design, patients are entered into the study based on the presence or absence of an exposure (or risk factor) of interest (Fig. 1). These two groups (i.e., those with the exposure and those without the exposure) are then compared to determine if they differ with regard to development of the outcome of interest. Whether a cohort study is prospective or retrospective depends on when it is conducted with regard to when the outcome of interest occurs. If patients are identified as exposed or unexposed and then followed forward in time to determine whether they develop the outcome, it is a prospective cohort study. If the study is conducted after all outcomes have already occurred, it is a retrospective cohort study. As an example, one might identify all patients who receive a FQ in the hospital (i.e., the exposed) and compare them to patients who do not receive a FQ (i.e., the unexposed). These groups could then be followed forward to determine what proportion of patients in each group develops the outcome of interest (i.e., FQREC infection).
The cost-effectiveness of biologic versus non-biologic treatments and the health-related quality of life among a sample of patients with inflammatory bowel disease in a tertiary care center in Saudi Arabia
Published in Journal of Medical Economics, 2020
Yazed AlRuthia, Majid Almadi, Abdulrahman Aljebreen, Nahla Azzam, Wejdan Alsharif, Hala Alrasheed, Ghadah Almuaythir, Maria Saeed, Baraa HajkhderMullaissa, Othman Alharbi
This investigation was designed as a retrospective cohort study. Patients 18 years of age or older, with a diagnosis of UC or CD and without a diagnosis of cancer, were identified using the electronic health records of King Khalid University hospital in Riyadh, Saudi Arabia. King Khalid University Hospital is a 1200-bed teaching hospital affiliated with King Saud University, which has the oldest school of medicine in the kingdom. The hospital provides tertiary care services to all Saudi citizens and legal residents on a referral basis, and has the largest IBD registry in Saudi Arabia. Two groups of patients who received treatment from January 2013 to December 2015 were compared; the groups consisted of patients treated with biologics alongside non-biologic therapies, and patients treated with non-biologic therapies only. The hospital’s IBD registry was used to retrieve data on the patients’ socio-demographic characteristics, resource utilization, disease behavior, and severity of the disease. HRQoL was assessed at the initiation of treatment and six months later using the Arabic version of the standardized EuroQol 5 Dimensional 3 Level (EQ-5D-3L) questionnaire with a visual analog scale (VAS)23,24. This was performed among a sample of newly referred patients to assess the impact of the treatments on patients’ HRQoL, and inform decisions related to the effectiveness of the prescribed treatment regimens. The study was approved by the Institutional Review Board of King Saud University College of Medicine (project no. E-11-538).
Efficacy of 0.1% tacrolimus in long-term management of erosive lichen planus
Published in Journal of Dermatological Treatment, 2021
Amber Kiyani, Kanwal Sohail, Muhammad Humza bin Saeed
This study was approved by the ethical review committee of Riphah International University (Ref No. IIDC/IRC/2019/05/001). It was designed as a retrospective cohort study. Retrospective data on 12 patients that were treated with 0.1% tacrolimus during the past 3-year period at Islamic International Dental Hospital, Islamabad, Pakistan, was collected. It was ensured that the selected patients met with clinico-pathological parameters of erosive OLP like erythema, erosions, pain, difficulty in food consumption, and biopsy-proven diagnosis. It was also ensured that these patients were non-responsive to conventional treatment with topical corticosteroids, and had at least a 12-month follow-up available with 3–6 months follow up interval usually coinciding with disease flare ups. The patients with other morphological type of OLP and those who were not biopsy proven were excluded from the study.
Use of indwelling pleural catheters for patients with hematological malignancies and malignant pleural effusions
Published in Canadian Journal of Respiratory, Critical Care, and Sleep Medicine, 2022
Ali Malik, Michael A. Mitchell, Inderdeep Dhaliwal, Kayvan Amjadi
This study has limitations that should be addressed. Our study reports hematological malignancies broadly as lymphoma, leukemia, or multiple myeloma. However, there are various subtypes of each that may have different treatment options and prognosis. We did not analyze each subtype separately given the low numbers in some subgroups would have precluded any meaningful interpretation. Next, use of chemotherapy and other treatments options was not accounted for in the analysis given the heterogeneity and complexity of treatment durations and regimes for these patients. As discussed, the effectiveness of chemotherapy in reducing time to pleural effusion resolution remains an important topic for future research. Lastly, an important limitation of using a retrospective cohort study design is the potential for complications being missed if they were not identified in the health records. Patients may have sought care at alternative health care facilities which would not have been captured in our electronic medical records and, therefore, would lead to an underestimated incidence of complications.
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- Cohort Study
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- Cohort
- Risk Factor
- Treatment & Control Groups
- Incidence