Table 2

Possible qualitative evidence synthesis methods to address aspects of complexity in systematic reviews and guidelines

MethodExplanationAspects of complexity that QES may be suitable to address4 7
Thematic synthesis
(Thomas and Harden)24
Pros: Most accessible form of synthesis. Clear approach, can be used with data that are quite ‘thin’ to produce descriptive themes and where data are ‘thicker’ to develop descriptive themes into more in-depth analytic themes. These themes then need to be completely integrated within any quantitative synthesis.
Cons: May be limited in interpretive ‘power’ and risks being used over simplistically and thus not truly informative for guideline development.
System adaptivity: Why does the system change
Emergent properties
Balance of health benefits and harms
Sociocultural acceptability of an intervention
Framework synthesis
(Oliver et al)49
Best fit framework synthesis
(Carroll et al)50
Pros: Works well within reviews of complex interventions due to the extent of the complexity that any framework can accommodate, including representation of theory. The framework allows a clear mechanism for integration of qualitative and quantitative evidence in an aggregative way—see Noyes et al.8
Works well where there is broad agreement about the nature of interventions and their desired impacts.
Cons: Requires work on how to identify, select and justify choice of framework.
A framework may only be revealed as inappropriate once extraction/synthesis is under way.
Risk of simplistically forcing data into a framework for expedience.
Interactions between components of complex interventions
Interactions of interventions with context
Multiple (health and non-health) outcomes
Balance of health benefits and harms
Sociocultural acceptability of an intervention
Feasibility and health system considerations
Meta-ethnography (Noblit and Hare)36Pros: Primarily interpretive synthesis method leading to creation of descriptive as well as new high-order constructs. Descriptive and theoretical findings can help inform guideline development. Requires primary studies to predominantly have data that are ‘thick’/rich.
Cons: Complex methodology and synthesis process that requires a highly experienced team. Can take more time and resources than other methodologies. Theoretical findings may be a combination of empirical evidence, expert opinion and conjecture to form hypotheses. May not satisfy requirements for an audit trail (although new reporting guidelines will help overcome this).45 More work is needed to determine how CERQual51 can be applied to theoretical findings. May be unclear how higher level findings translate into actionable points.
What ‘is’ the system. How can it be described?
Interactions between components of complex interventions
System adaptivity: Why does the system change
Balance of health benefits and harms
Sociocultural acceptability of an intervention
  • CERQual, Confidence in the Evidence from Qualitative Reviews; QES, qualitative evidence synthesis.