| 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 |
[11] Metronidazole, oral Bignell C, Fitzgerald M; Guideline Development Group; British Association for Sexual Health and HIV UK. UK national guideline for the management of gonorrhoea in adults, 2011.Int J STD AIDS. 2011 Oct;22(10):541-7. http://www.ncbi.nlm.nih.gov/pubmed/21998172
Metronidazole, oral: Workowski KA, Berman S; Centers for Disease Control and Prevention (CDC). Sexually transmitted diseases treatment guidelines, 2010.MMWRRecomm Rep. 2010 Dec 17;59(RR-12):1-110. Erratum in: MMWRRecomm Rep. 2011 Jan 14;60(1):18. Dosage error in article text. http://www.cdc.gov/std/treatment/2010/