Effectiveness of the national German quitline for smoking cessation: study protocol of a randomized controlled trial

Table 1 Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) diagram

	STUDY PERIOD
	Recruitment	Enrolment	Allocation	Post-allocation
TIMEPOINT	-t₂	-t₁	0	t₁	t₂	t₃	t₄
TIMEPOINT	Screening	Baseline assessment	Randomization	Intervention	Post assessment	Follow-up assessment	Biochemical verification
ENROLMENT:
Eligibility screen	X
Informed consent	X	X			X	X	X
Randomization			X
INTERVENTIONS:
Telephone counselling				X
Self-help brochure				X
ASSESSMENTS:
Socio-demographic characteristics	X	X
Smoking-related variables		X			X	X
Health status		X			X
Received social support					X
7-day point prevalence abstinence					X	X
Prolonged abstinence						X
Number of cigarettes smoked per day	X	X			X	X
Nicotine dependence		X			X	X
Number and duration of quit attempts					X	X
Occurrence of abstinence of at least 24 hours					X	X
Motivation to quit	X	X			X	X
Implementation of smoking restrictions at home		X			X	X
Smoking-related cognitions		X			X
Coping strategies		X			X
Use and acceptability of the received intervention					X
Breath carbon monoxide (CO)							X

Note: -t2: recruitment of participants by a market research company using a screening questionnaire; −t1: baseline assessment; 0: randomization of participants to either the intervention or control condition; t1: intervention (telephone counselling or self-help broschure); t2: post assessment 3 months after baseline assessment; t3: follow-up assessment 12 months after baseline assessment; t4: biochemical verification: 20% random sample of participants who reported 7-day point prevalence abstinence at 12-month assessment