CHAPTER 2 LITERATURE REVIEW
The preceding chapter provided an overview of the study focusing on the background of the research problem, hypothesises, objectives, key concepts, theoretical framework and research methodology. This chapter presents the process applied for the development of the literature search protocol and literature reviewed to capture the existing scientific knowledge in relation to the proposed research topic, which is food-based interventions as a strategy to address iron-deficiency and anaemia during pregnancy.
A literature review can be defined as a synthetic review and summary of what is known and what is unknown regarding the topic of a scholarly body of work, including the current work within the existing knowledge (Maggio, Sewell & Artino 2016:297). A systematic review is research undertaken to identify, evaluate, and synthesize the results of individual studies on a particular topic, making reliable data available in a usable form (Stern, Jordan & McArthur 2014:53). The literature review helps the researcher to ‘‘join the conversation’’ by providing context, informing methodology, identifying innovation, minimizing duplicative research, and ensuring that professional standards are met. Literature review helps the researcher to articulate clear goals, show evidence of adequate preparation, select appropriate methods, communicate relevant results, and to engage in reflective critique (Maggio et al 2016:297).
In order to achieve this, the review process must be well developed and pre-planned to reduce researcher bias and eliminate irrelevant or low-quality studies. Typically, a systematic review is planned by developing a protocol, which forms the foundation of the entire process (Butler, Hall & Copnell 2016:1). Therefore, the search protocol applied for this review and detailed discussion of the appraised themes is presented here below.
SEARCH PROTOCOL AND STRATEGY
Developing a search strategy protocol is an iterative process which involves continual assessment and refinement and provides the foundation for search strategy (Aromataris & Riitano 2014:49). The review protocol provides a predetermined plan to ensure scientific rigour and minimize potential bias. It also serves as a guide throughout the process and helps maintain focus on the chosen topic (Joanna Briggs Institute [JBI] 2015:6).
In this review, the researcher employed the Joanna Briggs Institute (JBI) approach for study selection and appraisal of quantitative (which measures the effectiveness of an intervention) and qualitative (which examines individual meaning and experience) evidence to develop the strategy as discussed by Porritt, Gomersall and Lockwood (2014:47). According to Porritt et al (2014:47) and JBI (2015:6), reviewers should take the following steps for a rigorous literature review and the protocol needs in order to contain their details:
Formulate a review objective and question. Identifying keywords for search.
Define inclusion and exclusion criteria to select literature. Identify databases to be searched.
Perform a comprehensive search of the literature. Select studies for critical appraisal.
Appraise the quality of the selected studies using one or more standardized tools. Extract data according to a template.
Analyse, synthesize, and summarize data.
Write up findings and draw conclusions (and in some cases make recommendations for practice, policy, or research).
The review question and aim
Determining the question is one of the first steps in planning a systematic review because it largely establishes the conduct of the review. A clear question will not only guide researchers in conducting a review, but it will also help readers to discern whether or not they should read it (Stern et al 2014:53). Before embarking on the search, the reviewer will need to understand the review question and what information is needed to address it (Aromataris & Riitano 2014:50). The review question is also used to design the overall study aim. The study aim should be a clear statement of the intention of the review and is typically phrased as a statement (Butler et al 2016:2).
According to Stern et al (2014:53), the good question should incorporate the four elements included in the PICO mnemonic: Population, Intervention, Comparison intervention and Outcome Measures. While a variety of mnemonics exists to help reviewers structure the review question, PICO is the preferred choice for question development in quantitative reviews. Its variants PICOS and PICOT, where S stands for study designs (indicating which study designs, such as randomized controlled trial or diagnostic study, are eligible to answer the review question) and T stands for time frame (a period over which outcomes are assessed) can also be used (Stern et al 2014:54).
In this review, the researcher employed PICO and developed the following focused question to design the search strategy: What is the effectiveness of food-based interventions as a strategy in improving the iron status and thus decreasing anaemia level of pregnant women? Based on this focused review question, the aim of the review contended on the global and national perspectives of the magnitude and consequence of maternal iron-deficiency anaemia, as well as experiences, challenges and opportunities of food-based strategies and interventions as effective and sustainable approaches to improve iron status and thus addressing iron-deficiency anaemia among pregnant women.
Keywords and search terms
Aromataris and Riitano (2014:50) state that, once the review question and aim are developed, the researcher needs to identify the terms or synonyms, often referred to as keywords or free-text words, articulated in the question and create a logic grid or concept map. In a logic grid for a review of the effectiveness of an intervention, each column represents a discrete concept that is generally aligned with each element of the PICO mnemonic. These lists of keywords then form the basis of the search strategy. As recommended in Butler et al (2016:2), the researcher conducted a brief search of literature before planning the review, to identify search keywords, appropriate databases and the inclusion and exclusion criteria prior to the final review.
In this review, the researcher thus applied the PICO mnemonic framework (Aromataris & Riitano 2014:50) and identified the following search keywords and terms: iron deficiency, iron-deficiency anaemia, anaemia, anaemia during pregnancy, consequence of anaemia, prevention of anaemia, iron-folic acid supplementation, pregnant women, maternal nutrition, food-based strategies, food-based interventions, dietary intervention, dietary guideline, dietary diversity, dietary practice, dietary knowledge, nutrition education, nutrition counselling, dietary intervention, dietary iron, iron bioavailability, dietary randomized control trials, iron intervention, iron absorption, iron intake, dietary iron, ascorbic acid, vitamin C, iron-rich vegetables and fruits and dietary efficacy intervention, east Ethiopia.
Regardless of whether the review involves quantitative or qualitative research (or both), criteria exist that must be addressed in the protocol such as inclusion criteria and methods. Inclusion criteria determine which research articles will be selected. In order for a reader to understand the focus of the review (and its limitations), the reviewers thus need to be precise in outlining the inclusion criteria (Stern et al 2014:56).
As stated in Stern et al (2014:56) and Porritt et al (2014:48), the researcher considered the following points while developing the inclusion criteria: the types of studies to be included (such as randomised control trials or qualitative studies); the intervention under investigation (such as dietary interventions); the outcome (the effectiveness of dietary interventions); the population (such as pregnant women); publication language and the time period.
In order to limit irrelevant sources, the researcher used the inclusion criteria listed below to identify literature sources relevant to the study:
Literature with randomized controlled trial and qualitative designs.
Literature on the dietary and nutrition interventions on iron and anaemia.
Literature assessing the public health significance of iron-deficiency anaemia.
Literature assessing the effectiveness of the food-based intervention in improving iron status in pregnant women.
Once the focused question and inclusion criteria are developed, the researcher designed the search strategy. The search strategy is one of the most important parts of the systematic review protocol because it outlines a priori strategies that reviewers will use to find, select, appraise and utilize the data (Butler et al 2016:2). Identifying and understanding relevant studies increase the likelihood of designing a relevant, adaptable, generalizable, and novel study that is based on educational or learning theory and can maximize impact (Maggio et al 2016:298).
The researcher applied the three approaches as stated in Aromataris and Riitano (2014:54) and Butler et al (2016:3) for the search strategy namely: identifying and search of relevant databases, examination of reference lists, or hand searching key journals in the area of interest and the grey literature sources. Gray literature often appears in the form of government or institution reports and newsletters and even in blogs, conference proceedings, census reports, or non-independent research papers (Aromataris and Riitano 2014:55).
Accordingly, for this review, the researcher searched various sources are including Google Scholar, Myunisa library, BMC Health Services Research, Pubmed/ MEDLINE, JBI Database, ResearchGate, International and National Organizations’ and Universities’ Databases. The researcher applied both alternative and the combination of keywords to search literature from the databases. In order to help with the keyword combinations, the three ‘Boolean Operators’ commands; “AND”, or “OR”, and “NOT” were used as stated in Aromataris and Riitano (2014:52).
Appraisal and synthesis of literature
According to Porritt et al (2014:48), the purpose of the critical appraisal is twofold. First, reviewer excludes studies which are of low quality and whose results may, therefore, compromise the validity of the recommendations of the review. Second, the reviewer identifies the strengths and limitations of the included studies. The latter is important: an interpretation of the studies’ results must be sensitive to the characteristics of the studied populations, as well as to how weaknesses in the study designs have affected those results.
Data synthesis is the final stage of writing a systematic review protocol (Butler et al 2016:6). According to Munn, Tufanaru and Aromataris (2014:49), while synthesized data in a systematic review are the results (or outcomes) extracted from individual research studies relevant to the systematic review question, the synthesis makes up the results section of the review.
After the researcher gathered the appropriate literature that met inclusion criteria; including articles, global and national dietary guidelines, recommendations, protocols, survey reports and books relevant to the proposed study topic, the studies were appraised based on the JBI Checklist for critical appraisal of quantitative studies and randomized control trials as stated in Porritt et al (2014:48-49). Quantitative studies are appraised to identify sources of bias (selection, performance and attrition). While examining the effectiveness of an intervention, randomized control trials are evaluated in terms of their internal validity and external validity. High internal validity means that the differences observed between groups are related to the intervention tested in the trial (Melnyk & Overholt 2011:433; Spieth, Kubasch, Penzlin, Illigens, Barlinn & Siepmann 2016:1343). External validity, on the other hand, refers to the extent to which the results of the study can be generalized to groups, populations, and contexts that did not participate in the study (Porritt et al 2014:48-49)
Once the researcher critically appraised the studies, the researcher then synthesised the data in two stages: an initial overview and the final critical review of their content using the PQRS (Preview, Question, Read, Summarise) system method, as stated in Cronin, Ryan and Coughlan (2008:41). Cronin et al (2008:41) describe that the method not only keeps the reviewer focussed and consistent but also ultimately facilitates easy identification and retrieval of material particularly if a large number of publications are reviewed. The researcher also used indexing and summary form to assist the process keeping records of the sources and full references for further tracing.
From the initial review, the researcher constructed the major themes and subthemes based on the summary of the review and made the synthesis in a direction to the study question and aim. Since the study question emphasizes the effectiveness of dietary interventions in relation to improvements in maternal iron status, the researcher gave particular attention to review dietary theoretical frameworks, research designs, data collection methods, intervention tools and analysis methods; and relate their strengths and limitation with respect to the desired effect size of the interventions; while focussing on nutrition education, dietary vitamin C and iron absorption. This further assisted the researcher to update the data collection and nutrition education tools with respect to their comprehensiveness, relevance and validity. All literature reviewed are sourced and referenced.
The researcher synthesised the literature review based on the systematized major themes and subthemes that emerged from the appraisal. Table 2.1 depicts the summary of the systematized themes.
CHAPTER 1: ORIENTATION TO THE STUDY
1.2. BACKGROUND TO THE RESEARCH PROBLEM
1.3. STATEMENT OF THE RESEARCH PROBLEM
1.4. AIM AND OBJECTIVES OF THE STUDY
1.5. SIGNIFICANCE OF THE STUDY
1.6. DEFINITIONS OF KEY CONCEPTS
1.7. OPERATIONAL DEFINITIONS
1.8. THEORETICAL FRAMEWORK
1.9. RESEARCH METHODOLOGY
1.10. ETHICAL CONSIDERATIONS
1.11. SCOPE OF THE STUDY
1.12. STRUCTURE OF THE THESIS
CHAPTER 2: LITERATURE REVIEW
2.2. SEARCH PROTOCOL AND STRATEGY
2.3. SYSTEMATIZED THEMES
2.4. LIMITATION OF LITERATURE REVIEW
CHAPTER 3: RESEARCH DESIGN AND METHOD
3.2. RESEARCH DESIGN
3.3. RESEARCH METHODS
3.4. INTERNAL AND EXTERNAL VALIDITY OF THE STUDY
CHAPTER 4: ANALYSIS, PRESENTATION AND DESCRIPTION OF THE RESEARCH FINDINGS
4.2. RESEARCH RESULTS
CHAPTER 5: DEVELOPMENT OF FRAMEWORK FOR INTEGRATED FOOD-BASED STRATEGY
5.2. OVERVIEW OF RESEARCH FINDINGS
5.3. DEVELOPMENT OF FRAMEWORK FOR INTEGRATED FOOD-BASED STRATEGY
CHAPTER 6: CONCLUSIONS AND RECOMMENDATIONS
6.2. RESEARCH DESIGN AND METHOD
6.3. SUMMARY OF THE RESEARCH FINDINGS
6.6. CONTRIBUTIONS OF THE STUDY
6.7. LIMITATIONS OF THE STUDY
6.8. CONCLUDING REMARKS
LIST OF REFERENCES
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