Acknowledgement Firstly

Acknowledgement
Firstly, we would like to show our appreciation for having the opportunity to accomplish this assignment. This assignment was completed by all of the group members putting our efforts, giving credit to our lecturer who led us along the assignment. Besides, we would also like to thank to our family members as well as friends for giving us moral supports and advices throughout the whole assignment. Moreover, we would like to thank in particular our lecturer Assistant Professor Dr. Fatokun who encouraged us in completing this assignment. His enthusiasm to teach and guide us had motivated us exceedingly in completing our assignment.

Introduction
Case control is an observational studies which compares the patients who have disease otherwise outcome of interest with patients who are in healthy controls. It also interpreted as a study which used to determine the frequency of the factors that different from case and control.1 The frequency of exposure to risk factor is compared retrospectively that exists in each group in order to determine the relationship between risk factor and the outcome.2 First step of case control is to categorize between the case group which is the group with disease and control group where the patients in that particular group has no disease then determine if the groups differ with respect to suspected exposure factors.
Case-control study has several advantages. This study design permits the study of rare diseases, and also allows the study of diseases with long latency between exposure and manifestation. Besides, case-control study has also the advantage of studying multiple causes of disease. However, the major limitation of case-control study is that it may be subjected to recall bias as information obtained primarily based on interview. Moreover, data and information collected after disease had occurred can also induce recall bias due to false correspondence in the result reported between risk factor as well as outcome.3
In this assignment, the critical appraisal of evidence on the article titled “Tamoxifen and risk of contralateral breast cancer in BRCA1 and BRCA2 mutation carriers: a case-control study” is discussed by using the reference Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Statement checklist. There are total 22 items which act as a guideline in facilitating the process of critical appraisal of research studies.

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Critical appraisal of evidence derived from case-control study
Title and abstract
(a) Indicate the study’s design with a commonly used term in the title or the abstract
In this article, the author had indicated the study’s design with commonly used term at the top of the page with the title mentioned it was a case-control study.
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(b) Provide in the abstract an informative and balanced summary of what was done and what was found
The abstract had also provided relatively informative and balanced summary including the background, methods, findings and interpretation on what have they done and found in the study.
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Introduction
Backgound / rationale
Explain the scientific background and rationale for the investigation being reported
18002251805940The background of a study is vital as it allow the authors to report the significant history to the current study, describe the focus and gives an overview of what is known on a topic. It helps to summarize earlier findings as well as limitations that may be addressed by from the reported study. This may assist the readers to understand the rationale of the conducted study and to evaluate the study. In this study, the authors had summarizing data of previous findings.
Objective
State specific objectives, including any prespecified hypotheses
Objectives are the aims of a study, where sometimes include specified hypotheses. In this study, the author stated the objective of the study which was to investigate the potential benefit of tamoxifen in the reduction of risk of contralateral breast cancer among BRCA1 or BRCA2 mutation carriers. However, the hypotheses of this study were not stated by the authors. This may due to insufficient evidence from previous studies.
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Methods
Study Design
Present key elements of study design early in the paper
The author did not clearly presented the key elements of the study design and this will cause the readers unable to understand the basics of the study early in the paper. Thus author should stated clearly in order for reader to get informed.

Setting
Describe the setting, location, and relevant dates, including periods of recruitment, exposure, follow-up, and data collection.

In this article the study location, year in which the study was conducted and periods of recruitment are not described. Yet the follow up period are not specific in method part and it can be found in results part which clearly defined it.

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Result
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15621008505825History of tamoxifen use for first breast cancer was obtained by interview or by self administered questionnaire which were collected between 1980 and 2000.

However this study consist of weakness as setting and relevant dates of study conducted were not mentioned yet follow up period and exposure were given but it were not specific in method part.

Participants
(a) Give the eligibility criteria, and the sources and methods of case ascertainment and control selection. Give the rationale for the choice of cases and controls
Eligibility criteria is the guidelines for who can or cannot participate in the study . This is important as it help researcher to get accurate and meaningful results as well as make sure that people who could be made worse by participating in the study are not exposed to the risk .Besides that sources and methods of case ascertainment and control selection were clearly stated
in the study. In addition the rationale for the choice of cases and controls were welly discussed under method section.

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(b) For matched studies, give matching criteria and the number of controls per case.

Matching can help to increase a study’s efficiency by ensuring similarity in the distribution of variables between cases and controls in particular of the distribution of potential confounding variables.

In this study , age matched control with unilateral hereditary breast cancer and residence matched at time of diagnosis were studied . The ratio of control to cases was 1 to 34 bilateral disease cases .
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Variables
Clearly define all outcomes, exposures, predictors, potential confounders, and effect modifiers. Give diagnostic criteria, if applicable.

Characteristics of cases with bilateral disease and of controls can be found in Table 1 while factors associated with treatment of first breast cancer was described in Table 2.

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Diagnostic criteria that reflect the different features of a disease (heterogeneity), with a view to accurately identify as many people with the condition as possible was discussed under mutation analysis.

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Cofounder is a variable that associate with the exposure and influence the outcome. It is clearly described in this passage where besides tamoxifen use the intervention of chemotherapy , oophorectomy and radiotherapy affect the risk of contralateral breast cancer in women with pathogenic mutation in BRCA1 OR BRCA2 gene.
Data sources/measurement
For each variable of interest, give sources of data and details of methods assessment (measurement). Describe comparability of assessment methods if there is more than one group.

The source of data was clearly mentioned under study protocol. In this article it used primary data collection technique in which data were collected by interview or self –administered questionnaire.

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Bias5-6
Describe any efforts to address potential sources of bias.

Bias causes systematic deviations of study results from the truth. It is significant for viewers to understand the methods used to minimize the possible bias throughout the study. It is ideal that the examiners review the possible causes of bias before conducting their studies, and is advised that the contributors habitually appraise and describe the probability of bias while reporting the study, particularly the direction and magnitude.
In the study being appraised, the bias was stated under the method section, but not the ways to reduce it. Besides, the direction and magnitude of bias was not discussed.

To reduce the bias caused by the potential cofounding, the cofounders were included in the multivariate analysis.

In the discussion section, the authors did mention that they minimized the effect of survivor bias but again, the method of doing so was not described.

Study Size4-5
Explain how the study size was arrived at.

This study did not explain how the study size was arrived at. It did mention that the 209 eligible patients were selected from 1243 cases, but the calculation of sample size was not displayed and explained.

In order to get a point estimate with small confidence to significantly respond to the research questions, the study must be sufficiently big. Although small studies frequently yield valuable data, the broad confidence interval may imply lesser contribution to the current understanding. Investigators are recommended to outline applicable sample size calculation and specify the determinant of study size. Viewers should be notified if the study was terminated in advance when statistical significance was attained.6
For the viewers, confidence interval shows the precise statistic gained at the end of the study. In the article, the study size validity was mentioned to be 95% confidence level and p value less than 0.05.