Table 1 Typology of synthesis designs suggested in the literature

Frantzen and Fetters [40]

1. Convergent meta-integration: quantitative, qualitative, and mixed methods studies are synthesized without data transformation.

2. Convergent qualitative meta-integration: quantitative data are transformed into qualitative format.

3. Convergent quantitative meta-integration: qualitative data are transformed into quantitative format.

Each design can be of basic type (when a review includes quantitative and qualitative studies) or advanced type (when a review includes qualitative, quantitative, and mixed methods studies).

Heyvaert et al. [22]

An 18-design framework based on the emphasis of approaches (equal or dominant status of qualitative or quantitative approach), the temporal orientation (sequential or convergent), and the level of integration (partial or full integration).

Pluye and Hong [10]

1. Sequential exploratory: results of the qualitative synthesis inform the quantitative synthesis.

2. Sequential explanatory: results of the quantitative synthesis inform the qualitative synthesis.

3. Convergent: results of qualitative and quantitative studies are integrated using data transformation techniques.

Sandelowski et al. [8]

1. Segregated: qualitative and quantitative findings are treated separately.

2. Integrated: qualitative findings are transformed into quantitative data (quantitizing) or quantitative finding are transformed into qualitative data (qualitizing).

3. Contingent: cycle of research synthesis studies conducted to answer questions raised by previous synthesis.