| Level I | Good quality evidence |
Systematic review of RCTs with consistent findings High quality individual RCT |
| Level II |
Limited quality patient orientated evidence |
Systematic review of lower quality studies or studies with inconsistent findings Low quality clinical trial Cohort studies Case-control studies |
| Level III | Other |
Consensus guidelines, extrapolations from bench research, usual practice, opinion, disease-oriented evidence (intermediate or physiologic outcomes only), or case series |
[25] Prednisone: Leuppi JD., Schuetz P., Bingisser R., Bodmer M., Briel M., Drescher T., Duerring U., Henzen C., Leibbrandt Y., Maier S., Miedinger D., Muller B., Scherr A., Schindler C., Stoeckli R., Viatte S., von Garnier C., Tamm J. 2013. Short-term vs Conventional Glucocorticoid Therapy in Acute Exacerbations of Chronic Obstructive Pulmonary Disease. The REDUCE Randomized Clinical Trial. JAMA. Vol 309(21): 2223-2231 http://www.ncbi.nlm.nih.gov/pubmed/23695200