Table 1. Proportion of test requests, returns, overall testing and Chlamydia trachomatis (CT) positivity and associated factors in1072 young people invited by SMS for a retest.

	Proportion of tests requested		Proportion of those who requested a test		Testing		Positivity
	(1072 invitees)		(n = 369) who also returned the test		among 1072 invitees		among 206 tested invitees
	% (n)	aOR (95% CI)	% (n)	aOR (95% CI)	% (n)	aOR (95% CI)	% (n)	aOR (95% CI)
Overall	34.4 (369)		55.8 (206)		19.2 (206)		10.2 (21)
Number of days	Test request-invitation SMS:		Test return-request:		Testing-invitation SMS:
(median, IQR)	0 days (0–13)		19 days (7–36)		27 days (12–51)
Initial screening
Negative	29.3 (157)	1	54.8 (86)	1	16.0 (86)	1	7.0 (6)	1
Positive	39.6 (212)	1.5 (1.2–2.0)*	56.6 (120)	1.1 (0.7–1.7)	22.4 (120)	1.5 (1.1–2.0)*	12.5 (15)	2.0 (0.7–5.6)
Nationality^
Dutch	34.5 (357)		56.0 (200)		19.3 (200)		10.5 (21)
Non-Dutch	31.6 (12)		50.0 (6)		15.8 (6)		0 (0)
Years of age
16–22	32.8 (219)	1	53.4 (117)	1	17.5 (117)	1	10.3 (12)	1
23–30	37.0 (150)	1.3 (1.0–1.7)*	59.3 (89)	1.5 (0.9–2.2)	22.0 (89)	1.6 (1.2–2.2)*	10.0 (9)	1.0 (0.4–2.8)
Sex
Male	31.1 (142)	1	43.7 (62)	1	13.6 (62)	1	8.1 (5)	1
Female	36.9 (227)	1.3 (1.0–1.7)*	63.4 (144)	2.3 (1.5–3.5)*	23.4 (144)	2.1 (1.5–2.9)*	11.1 (16)	1.5 (0.5–4.5)
Screening test
3–12 months ago	37.2 (249)	1.3 (0.9–1.7)#	57.8 (144)	1.1 (0.7–1.8)	21.5 (144)	1.4 (0.9–1.9)#	9.7 (6)	0.9 (0.3–2.5)
13–20 months ago	29.8 (120)	1	51.7 (62)	1	15.4 (62)	1	10.4 (15)	1

*p<0.05,

^# p<0.10

CI: Confidence Interval; aOR: adjusted Odds Ratio, meaning that risk estimates were adjusted when applicable for initial screening result of the index, age of the index, sex of the index, timing of the screening test of the index

^{^}nationality was not included as a factor as nearly all participants had Dutch nationality