Systematic reviews have always been a cornerstone of Evidence Based Practice. "Is A better than B at treating C" was the initial formula, with randomized controlled trials providing the numbers to tally the evidence. Qualitative research was an awkward fit, sometimes granted a minor supporting role but most often excluded. As systematic reviews became more widely used and began to infiltrate the social sciences there began to emerge more questions that quantitative studies could not answer.
Qualitative researchers use interviews, focus groups, documents even multimedia files to gather their data. NVivo is designed to handle all of these data sources and is effective in all qualitative methodologies. See a good explanation of using NVivo for qualitative research, from the creators: QSR International.