Letters to the Editor
We sincerely welcome the constructive critical comments by Hannes and Aertgeerts. To date, there is little consensus on how to assess the quality of qualitative research.1 Despite the scarcity of empirical evidence to guide the selection of methodological criteria for including qualitative studies in systematic investigations, we believe that it is important to assess the quality of qualitative research to be able to protect against biased and diluted information. Still, we do acknowledge that our choices about methodological criteria may have affected the precision of our findings to some extent. Hence, below we explain the rationale for our selection criteria in response to the three points raised by Hannes and Aertgeerts.
First, with regard to methodological triangulation, we believe that using various research methods to study the same object is different from and more rigorous than studying the same object by means of replicating one research method with multiple observers or data collectors.
Second, we excluded primary studies for not being transparent about their approach to deriving themes from the data. In line with Hannes and Aertgeerts, we believe that reporting on theme derivation is still too diverse to allow an unambiguous methodological evaluation on data analysis.
Third, we selected studies that used theoretical or purposive sampling to ensure conceptual saturation. We believe that when saturation has not been achieved there may be an increased risk for primary studies to report spurious findings.
In conclusion, although some of the studies we excluded may provide information worth noting, we believe that we included those studies for which the presented data are neither ambiguous nor disputed. We hope that our review and the accompanying discussions on selection of studies will contribute to the consensus on which criteria to use for an assessment of methodological quality in qualitative research.
Maartje Swennen, MD, MSc
PhD fellow, Department of Clinical Epidemiology, Division Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, the Netherlands; firstname.lastname@example.org.
Geert van der Heijden, PhD
Professor, Department of Social Dentistry, Academic Centre for Dentistry (ACTA), University of Amsterdam and VU University Amsterdam, Amsterdam, the Netherlands.
1. Thomas J, Harden A. Methods for the thematic synthesis of qualitative research in systematic reviews. BMC Med Res Methodol. 2008;8:45