Table 2. Multivariable logistic regression analyses of predictors of non-response at the three follow-up data collection moments for participants who visited the STI clinic in Amsterdam.

	Baseline		3-week follow-up non-response			6-month follow-up non-response			1-year follow-up non-response
	N	%	N	%	aOR	N	%	aOR	N	%	aOR
					(95%CI)			(95%CI)			(95%CI)
Total	647		292	45		303	47		365	56
Number of partners in past six months
0–2 partners	222	34	94	32	-	93	31	1	117	32	-
3–4 partners	261	40	123	42	-	114	38	0.99 (0.68–1.43)	143	39	-
≥ 5 partners	164	25	75	26	-	96	32	1.73 (1.14–2.64)	105	29	-
Condom use at last sex act
No	504	78	235	81	-	239	79	-	300	82	1
Yes	143	22	57	20	-	64	21	-	65	18	0.70 (0.47–1.03)
Age at sexual debut
< 16 years	205	32	102	35	-	100	33	-	123	34	-
≥ 16 years	442	68	190	65	-	203	67	-	242	66	-
Health goals
Low/med (score < 4.00)	314	49	159	55	1	168	55	1	200	55	1
High (score ≥ 4.00)	333	52	133	46	0.77 (0.55–1.07)	135	45	0.65 (0.47–0.90)	165	45	0.65 (0.47–0.90)
Attitudes*
Low/med (score < 4.25)	265	41	136	47	1	140	46	-	167	46	-
High (score ≥ 4.25)	382	59	156	53	0.76 (0.54–1.06)	163	54	-	198	54	-
Social norms and support
Low/med (score < 3.20)	229	35	122	42	1	119	39	-	140	38	-
High (score ≥ 3.20)	418	65	170	58	0.65 (0.47–0.91)	184	61	-	225	62	-
Risk perception for CT (own risk)
Low/med (score < 27.50)	311	48	134	46	-	126	42	1	151	41	1
High (score ≥ 27.50)	336	52	158	54	-	177	58	1.51 (1.09–2.08)	214	59	1.70 (1.23–2.33)

* Attitudes regarding prevention of chlamydia

Footnote: Categories do not all add up to 100%, as missing values are not shown. Statistical associations are shown in in italic when the p-value is equal to or smaller than 0.1, and in bold when the p-value is equal to or smaller than 0.05. Only variables that were pre-selected in the univariable analyses are shown here.

Abbreviations: aOR = adjusted odds ratio, CI = Confidence Interval; Low/med = Low/medium, CT = Chlamydia; STI = Sexually Transmitted Infection.