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. 2016 Apr 4;175:599–612. doi: 10.1007/s00431-016-2715-9

Table 2.

Level of evidence of qualitative studies

Level of evidence a Characteristics
++ Credible meta-synthesis of qualitative studies
+ Credible study
+/- Study of which credibility is dubious
- Study of which credibility is minimal

a levels according to those set by the Dutch Institute for Healthcare Improvement (CBO)