Summary of findings 2. Selective COX‐2 inhibitors compared to non‐selective NSAIDs for acute low back pain.

Selective COX‐2 inhibitors compared to non‐selective NSAIDs for acute low back pain
Patient or population: adults (≥ 18 years of age) with acute low back pain (LBP) Setting: primary and secondary care settings, mainly general practice and outpatient clinics Intervention: selective COX‐2 inhibitors Comparison: non‐selective NSAIDs
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	№ of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with non‐selective NSAIDs	Risk with COX‐2 inhibitors
Change in pain intensity from baseline VAS (0 to 100; lower = better) Follow‐up ≤ 3 weeks (range 7 to 10 days)	The mean change in pain intensity from baseline in the non‐selective NSAID group ranged from 38 to 41	The mean change in pain intensity from baseline in the COX‐2 inhibitors group was 2.60 lower (9.23 lower to 4.03 higher)	‐	437 (2 RCTs)	⊕⊕⊝⊝ Lowa,b	MID is 10 points on a 0 to 100 scale
Disability ODI (0 to 50; lower = better) Follow‐up ≤ 3 weeks (range 7 to 10 days)	One trial reported a mean difference in disability score of ‐7.00 (95% CI ‐13.15 to ‐0.85) after 10 days, showing a statistically significant and clinically relevant difference in favour of the nimesulide arm. One trial reported a mean decrease in baseline disability of 32% in both the valdecoxib and diclofenac arm at 1 week follow‐up, showing no clear difference between study arms.		‐	437 (2 RCTs)	⊕⊕⊕⊝ Moderatea	MID is 5 points on a 0 to 50 scale
Proportion of participants experiencing global improvement % of dichotomized Likert scale Follow‐up ≤ 3 weeks (7 days)	One trial reported the percentage of participants who reported their pain relief as 'a lot better' or 'completely better' at 1 week follow‐up, which was similar in both the valdecoxib (80%) and diclofenac (81%) arm, showing no clear difference between study arms.			333 (1 RCT)	⊕⊕⊝⊝ Lowa,c
Proportion of participants experiencing adverse events Follow‐up range 10 to 37 days	Study population		RR 0.97 (0.63 to 1.50)	444 (2 RCTs)	⊕⊝⊝⊝ Very lowa,d
	248 per 1000	240 per 1000 (156 to 372)
Return to work (%) Follow‐up: N/A	Not reported		‐	‐	N/A
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; VAS: visual analogue scale; ODI: Oswestry Disability Index; RR: risk ratio; RCT: randomised controlled trial; N/A: not available; MID: minimal important difference
GRADE Working Group grades of evidence High certainty. We are very confident that the true effect lies close to that of the estimate of the effect Moderate certainty. We are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different Low certainty. Our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect Very low certainty. We have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect

^aDowngraded one level due to risk of bias. More than 25% of the included participants were from a study with high risk of bias.
 ^bDowngraded one level due to inconsistency. There is moderate to substantial heterogeneity with an I² of 57%, and a wide variance in point estimates.
 ^cDowngraded one level due to imprecision. The total number of events was far less than 300, leading to a wide confidence interval. 
 ^dDowngraded two levels due to imprecision. The total number of events was far less than 300, leading to a wide confidence interval. The 95% confidence interval includes both no effect and the threshold of appreciable benefit or harm.