Much of the research in quality of life (QoL), and the majority of publications in Quality of Life Research, have employed quantitative methods. Although these methods have value in facilitating rigor and reproducibility in clinical research studies, they have a concomitant risk of losing the subtlety and distinctions experienced by patients living with health problems. The field of QoL research would benefit from an increased awareness of the value of combining qualitative and quantitative approaches and from a renewed appraisal of best practices in the use of such mixed methods.

Qualitative frameworks and techniques for data collection offer a wide array of options for studying the lived experience of a disease and its treatment. Frequently used qualitative approaches to collect and analyze data and interpret results include phenomenology, grounded theory, and ethnography [1]. These approaches differ with regard to their essence. Phenomenology aims to understand the meaning of persons’ experiences. Grounded theory builds new theory and concepts from the ground up. Ethnography focuses on understanding “insider points of view” within a specific cultural or social group context. Qualitative data can be collected in a variety of ways, such as by in-depth interviews, focus groups, observation, and document evaluation. Important aspects to consider for enhancing the rigor of qualitative research are the criteria for selecting participants, determining sample size, establishing validity, controlling biases, and conducting the qualitative analyses. These aspects have all been described in texts, but guidance and oversight by an experienced qualitative researcher may be an optimal way to learn these skills and to choose the appropriate framework and methods [2]. Full reporting of how the work was done is also essential, and building on existing qualitative-specific criteria can be helpful [3–5].

Qualitative research has long been accepted in anthropology and sociology. In contrast, the emergence of qualitative research within the health field has triggered controversy. In a chapter on qualitative methods in health technology assessment, Murphy and Dingwall recount the key issues and positions that comprised this controversy [6]. Using quotes from thought leaders, they illustrate the views of opposing sides in the debate that pitted holistic social constructivism against hypothesis-driven empiricism during the 1980s and 1990s. Hypothesis-driven empiricism, the orderly system also known as “the scientific method,” was challenged as being only one viewpoint—“post-positivism”. Alternative viewpoints, such as social constructivism, were argued to provide a better framework for understanding complex issues, such as health [6, 7]. Some asserted that qualitative and quantitative methods arose from “radically incompatible” worldviews with such pervasive differences that a “separatist” viewpoint was the only option. It was common for faculty and students in graduate programs to take sides and be labeled (willingly or unwillingly) as either qualitative or quantitative people. Individual battles were fueled by language—a vocabulary filled with unfamiliar words (e.g., etic, emic, Hermeneutics), and familiar words given unfamiliar meanings (e.g., sampling, rich).

Fortunately, it appears that in recent years the paradigm wars have lost much of their heat. Newer editions of methodology texts have first added, and then expanded content on qualitative approaches, and it is now the norm for graduate students to be encouraged to acknowledge the literature, if not to gain hands-on skills and experience, in both qualitative and quantitative approaches [8, 9]. The post-positivist’s randomized clinical trial could determine which medication was superior for the average patient, and the social constructionist could interview individual patients and their caregivers in order to understand what it means to live with the disease and its treatment. The complementary nature of these endeavors is increasingly recognized in the literature [10, 11]. There are excellent examples of interdisciplinary teams bringing both qualitative and quantitative approaches to bear on complex health problems [12, 13], and overall, the number of articles containing qualitative research in MEDLINE has increased more than fourfold between 1980–1984 and 2006–2010 (see Fig. 1).

Fig. 1
figure 1

Qualitative research in MEDLINE, 1980 to present. The number of articles containing qualitative research published in the biomedical literature in each 5-year epoch from 1980 to the present was estimated using the number of articles retrieved by the following search strategy: (qualitative* or phenomenolog* or grounded theor* or ethnograph*).mp. [mp = title, original title, abstract, name of substance word, subject heading word, unique identifier] (120904). MEDLINE search conducted March 2, 2010

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Mixed methods are founded in pragmatism, using whatever rigorous approach works to gain useful insights [14]. Mixed methods enable us to place research efforts on a continuum from purely qualitative to purely quantitative, with intermediate points reflecting studies that have a blend of both. At the purely qualitative end of the spectrum, many studies demonstrate the use of constructivist grounded theory and involve in-depth interviews with a small number of people with a particular condition [15]. This approach allows for an in-depth exploration of the patient’s perspective of factors influencing their QoL. The disadvantage of this approach is that its external validity or generalizability is likely quite limited.

Other researchers employ both quantitative and qualitative methods, in varying proportions, either in parallel or in sequence. The expectations of regulatory authorities such as the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) regarding the establishment of evidence of content validity for patient-reported outcomes have served to both drive and legitimize mixed-method interdisciplinary efforts [16, 17]. Content validity needs to be established from patients’ own perceptions and hence qualitative methods are the preferred approach to generating item content for new patient-reported outcome measures in the target population. Examples of this approach utilize focus groups and cognitive interviews (qualitative) in developing and refining a new measure prior to applying classic or modern psychometric methods to establish validity and reliability (quantitative) [18]. This mixed-method approach has been adapted by the PROMIS investigators in their model of item-pool development [19].

Recently, in QLR, Robertson et al. [20] used in-depth interviews to explore the frames of reference used by a subsample of respondents to QoL measures in a large randomized controlled trial while Wolfe and Sirois [21] performed content analysis on the responses to the open-ended question “How has inflammatory bowel disease affected your daily activities?”, embedded within a structured cross-sectional survey of the well-being of people with inflammatory bowel disease (quantitative then qualitative).

Scientific rigor is required in the application and reporting of any methods, whether qualitative or quantitative [11]. As researchers in the field of QoL research grow to embrace the use of mixed methods, the need for qualified reviewers becomes more pressing. It would thus be important to expand the continuing-education opportunities at ISOQOL meetings to teach, discuss and disseminate current best practices in mixed methods [22]. Further, this would enable the QLR journal to have a cadre of reviewers who are qualified to judge and provide useful constructive feedback on the hopefully growing stream of mixed-method manuscripts.