Certainty of evidence and intervention's benefits and harms are key determinants of guidelines' recommendations

Many factors are postulated to affect guidelines developments. We set out to identify the key determinants.

a) Web-based survey of 12 panels of 153 "voting" members who issued 2941 recommendations; b) qualitative analysis of 13 panels of 311 attendees (panel members, systematic review teams and observers).

Compared with "no recommendations", when intervention's benefit outweigh harms (BH-balance), probability of issuing strong recommendations in favor of intervention was 0.22 (95%CI: 0.08 to 0.36) when certainty of evidence (CoE) was very low; 0.5 (95%CI:0.36 to 0.63) when low; 0.74 (95%CI 0.61 to 0.87) when moderate and 0.85 (95%CI:0.71 to 1.00) when high. No other postulated factor significantly affected recommendations. The findings are consistent with a J- curve model when recommendations are issued in favor but not against an intervention. Panelists often changed their judgments as a result of the meeting discussion (67% for CoE to 92% for balance between benefits and harms). The panels spent over 50% of their time debating CoE; the chairs and co-chairs dominated discussion.

CoE and BH-balance are key determinants of recommendations in favor of an intervention. Chairs and co-chairs dominate discussion. Panelists often change their judgments as a result of panel deliberation.