3.3 Introduction to qualitative systematic reviews

There is no hierarchy of evidence among methodologies for qualitative studies. A meta aggregative systematic review does not require any distinction between critical or interpretive studies. The units of analysis sought from qualitative papers are the findings, presented as themes, metaphors or concepts as identified by the researchers (not the reviewer). Accordingly, meta aggregative reviews include a range of methodological studies in order to capture the whole of a phenomenon of interest, rather than merely a one dimensional aspect. The rationale for this is that the traditions of the methodology employed in a study are considered to be embedded within the findings, rather than distinct to the findings. This implies that when a finding is extracted, the perspective or context that the study author intended for the finding is not lost, but is embedded in the extraction.

The synthesis of qualitative data

The perspectives of primary qualitative researchers has had a significant impact on development of methods for qualitative synthesis. It has been proposed that this may in part due to the fact that primary qualitative researchers conceive of paradigms as emblematic of their ability to situate not only themselves but also their work in relation to knowledge generation. As Chin and Jacobs (1987) assert, knowledge as subjective truth requires a researcher or author to explicitly state their chosen paradigm as it has implications for how a reader will understand the written word and how the methodology and methods will be read and understood.

This is no less appropriate in qualitative synthesis. Indeed, Sandelowski and Barroso (2007), although reluctant to create or promulgate rules for qualitative synthesis, posit that the first rule (if any should exist) is that the methods of synthesis should not violate the philosophic foundations (i.e. paradigm) of the approach used. It is evident then that while synthesis is a different process to primary research, the principles and processes of qualitative synthesis must be sensitive to the core assumptions of the critical and interpretive paradigms. The synthesis of qualitative data is also contested among qualitative researchers themselves, based on philosophical and methodological differences between the different qualitative research approaches (Sandelowski et al. 1997, Thorne et al. 2004).

Of the views that characterize the ongoing debate surrounding the meta-synthesis of qualitative evidence, one area of focus is the perceived degree of ‘interpretiveness” of the approach to data analysis. There has been extensive debate in the literature as to what constitutes an’interpretive’ review, and whether some qualitative synthesis approaches are more or less interpretive than others. These debates tend to focus on the synthesis component of the systematic review, and attempt to classify the whole of a review methodology on the basis of whether the synthesis component can be labelled as either ’inductive’ or ’deductive’. A further issue is whether qualitative synthesis methodologies should fit within the accepted conventions for systematic review or whether qualitative synthesis methodologies should be more reflective of primary qualitative methodologies. Approaches to qualitative synthesis that are more aligned with primary qualitative methodologies may not require reviewers to undertake comprehensive searching, appraisal to establish quality is not considered important, and data extraction and synthesis may be iterative and based upon the re-interpretation of published data.