Comparison 1. Intranasal corticosteroids versus placebo.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Disease severity ‐ measured as change from baseline using the Chronic Sinusitis Survey at 20 weeks	1	134	Mean Difference (IV, Fixed, 95% CI)	2.84 [‐5.02, 10.70]
2 Disease severity ‐ global symptom score, measured as proportion of patients who improved	1	109	Risk Ratio (M‐H, Fixed, 95% CI)	2.78 [1.76, 4.40]
3 Disease severity ‐ combination of individual symptom scores, measured on a 0 to 3 scale as change from baseline at 12 to 20 weeks	6		Mean Difference (IV, Fixed, 95% CI)	Subtotals only
3.1 Average symptom score (4 EPOS domains)	2	243	Mean Difference (IV, Fixed, 95% CI)	‐0.26 [‐0.37, ‐0.15]
3.2 Average symptom score (3 EPOS domains ‐ nasal blockage, rhinorrhoea, loss of sense of smell)	4	1345	Mean Difference (IV, Fixed, 95% CI)	‐0.31 [‐0.38, ‐0.23]
3.3 Average symptom score (2 EPOS domains ‐ nasal blockage and rhinorrhoea)	6	1702	Mean Difference (IV, Fixed, 95% CI)	‐0.31 [‐0.38, ‐0.24]
4 Disease severity ‐ individual symptoms, measured as average change from baseline at 12 to 20 weeks (range 0 to 3 points)	6		Mean Difference (IV, Random, 95% CI)	Subtotals only
4.1 Nasal blockage	6	1702	Mean Difference (IV, Random, 95% CI)	‐0.40 [‐0.52, ‐0.29]
4.2 Rhinorrhoea	6	1702	Mean Difference (IV, Random, 95% CI)	‐0.25 [‐0.33, ‐0.17]
4.3 Loss of sense of smell	4	1345	Mean Difference (IV, Random, 95% CI)	‐0.19 [‐0.28, ‐0.11]
4.4 Facial pain/pressure	2	243	Mean Difference (IV, Random, 95% CI)	‐0.27 [‐0.56, 0.02]
5 Adverse events ‐ epistaxis	13	2508	Risk Ratio (M‐H, Fixed, 95% CI)	2.74 [1.88, 4.00]
5.1 With nasal polyps	10	2262	Risk Ratio (M‐H, Fixed, 95% CI)	3.03 [2.00, 4.59]
5.2 Without nasal polyps	3	246	Risk Ratio (M‐H, Fixed, 95% CI)	1.49 [0.59, 3.78]
6 Adverse events ‐ local irritation	11	2124	Risk Ratio (M‐H, Fixed, 95% CI)	0.94 [0.53, 1.64]
6.1 With nasal polyps	9	2045	Risk Ratio (M‐H, Fixed, 95% CI)	0.93 [0.52, 1.67]
6.2 Without nasal polyps	2	79	Risk Ratio (M‐H, Fixed, 95% CI)	1.02 [0.15, 6.84]
7 Endoscopy score (bilateral polyps score) measured change from baseline (range 0 to 6 points)	4	1417	Mean Difference (IV, Random, 95% CI)	‐0.58 [‐0.90, ‐0.26]
7.1 With nasal polyps	4	1417	Mean Difference (IV, Random, 95% CI)	‐0.58 [‐0.90, ‐0.26]
8 Endoscopy score (polyps size) ‐ measured as numbers with improvement at longest available follow‐up	5	676	Risk Ratio (M‐H, Random, 95% CI)	1.77 [1.06, 2.95]
8.1 With nasal polyps	5	676	Risk Ratio (M‐H, Random, 95% CI)	1.77 [1.06, 2.95]
9 Endoscopy score (polyp size) ‐ measured as numbers with improvement at longest available follow‐up	8	1984	Odds Ratio (Random, 95% CI)	2.07 [1.48, 2.91]
9.1 With nasal polyps	4	1417	Odds Ratio (Random, 95% CI)	2.43 [1.46, 4.06]
9.2 With nasal polyps from dichotomous data	4	567	Odds Ratio (Random, 95% CI)	1.73 [1.19, 2.51]
10 CT score (overall) ‐ measured using Lund‐Mackay score (max 24 points) at 3 months	1	47	Mean Difference (IV, Fixed, 95% CI)	‐4.82 [‐7.27, ‐2.37]