Table 3.

Factors associated with a positive test result for Chlamydia trachomatis in Basel-Stadt residents (crude and adjusted odds ratios)

	N*	OR (95% CI)	P value†	aOR‡ (95% CI)	P value†
Sex	20 370		<0·0001		<0·0001
Male	2832	1		1
Female	17 538	0·39 (0·34–0·45)		0·26 (0·18–0·38)
Age group, yr	20 370		<0·0001		<0·0001
0–14	199	0·19 (0·03–1·38)		—
15–19	1365	4·52 (3·50–5·83)		—
20–29	7828	3·24 (2·63–3·97)		—
30–39	6648	1·58 (1·27–1·98)		—
≥ 40	4330	1		—
Test year	20 370		0·018		0·050
2002	1392	0·96 (0·72–1·30)		0·93 (0·69–1·26)
2003	1526	1·17 (0·89–1·53)		1·12 (0·85–1·47)
2004	1941	1·27 (0·99–1·62)		1·21 (0·94–1·56)
2005	2193	1·23 (0·97–1·56)		1·21 (0·95–1·55)
2006	2272	1·32 (1·05–1·67)		1·30 (1·03–1·65)
2007	2420	0·97 (0·76–1·24)		0·96 (0·75–1·24)
2008	2639	1·37 (1·09–1·71)		1·33 (1·06–1·67)
2009	2828	1·05 (0·83–1·32)		1·08 (0·85–1·36)
2010	3159	1		1
Laboratory	20 370		0·009		0·038
A	1207	1·34 (1·07–1·69)		1·37 (1·08–1·74)
B	3230	1·04 (0·88–1·22)		1·12 (0·94–1·33)
C	4079	0·86 (0·73–1·01)		1·15 (0·97–1·36)
D	11854	1		1
Test method	20 370		0·035
Biostar OIA	46	0·39 (0·05–2·85)		—
LCR	53	0·69 (0·17–2·85)		—
PCR	1108	1·48 (1·17–1·88)		—
Versant kPCR	3230	1·08 (0·92–1·28)		—
Abbott PCR	4347	1·03 (0·88–1·20)		—
Cobas Amplicor PCR	11586	1		—
Males aged, yr	2832		—		<0·0001
0–14	79	—		—
15–19	85	—		1·96 (0·94–4·09)
20–29	661	—		4·54 (3·31–6·22)
30–39	826	—		2·58 (1·87–3·57)
≥ 40	1181	—		1
Females aged, yr	17 538		—		<0·0001
0–14	120	—		0·51 (0·07–3·76)
15–19	1280	—		7·99 (5·69–11·21)
20–29	7167	—		4·76 (3·51–6·44)
30–39	5822	—		1·87 (1·35–2·60)
≥ 40	3149	—		1

OR, Odds ratio; aOR, adjusted odds ratio; CI, confidence interval.

^*N, Number of observations (tests).

^†From likelihood ratio test.

^‡Adjusted odds ratio; adjusted for sex, age group, test year, laboratory and sex × age group interaction.