Procalcitonin guided antibiotic therapy and hospitalization in patients with lower respiratory tract infections: a prospective, multicenter, randomized controlled trial

Table 2 Required total sample size

True assumed failure rate in both arms	Required total sample size
	Δ = 5% Power 90% (80%)	Δ = 7.5% Power 90% (80%)	Δ = 10% Power 90% (80%)
10%	1278 (932)	578 (426)	330 (244)
15%	1792 (1302)	806 (588)	458 (334)
20%	2232 (1624)	1002 (730)	570 (418)

Sample size calculation for the primary endpoint, i.e. required sample size to conclude at the one-sided 5%-level that the disease-specific failure rate in PCT-guided arm is at most Δ higher compared to management with enforced guidelines with a power of 80–90%.