| 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 |
[2] Capparelli EV, and Pediatric AIDS Clinical Trials Group 331 Investigators. Pharmacokinetic and tolerance of zidovudine in preterm infants. Journal of Pediatrics. 2003, January; 142 (1):47-52.