| 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 |
[35] Chest x-ray diagnosis (diagnosis of community acquired pneumonia): Boyles TH, Brink A, Calligaro GL, Cohen C, Dheda K, Maartens G, et al; South African Thoracic Society; Federation of Infectious Diseases Societies of Southern Africa. South African guideline for the management of community-acquired pneumonia in adults. J Thorac Dis. 2017 Jun;9(6):1469-1502. https://www.ncbi.nlm.nih.gov/pubmed/28740661