High rates of anorectal chlamydia in women: a cross-sectional study in general practice

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Figure 1. Distribution of cycle threshold (Ct) values of samples positive in the Chlamydia trachomatis polymerase chain reaction (PCR) test

Table 1. Population characteristics and Chlamydia trachomatis prevalence by indication for rectal testing

	Standard indicationN = 211^a% (n/N)		Experimental indicationN = 414^b% (n/N)		TotalN = 497% (n/N)
Age, years
≤21	15.6	(33/211)	20.0	(83/414)	21.7	(108/497)
22–28	44.1	(93/211)	46.4	(192/414)	45.1	(224/497)
>28	40.3	(85/211)	33.6	(139/414)	33.2	(165/497)
Chlamydia prevalence^c
Any site	12.0	(25/208)	16.7	(68/408)	17.8	(87/490)
Urogenital	10.1	(21/207)	14.5	(59/406)	15.4	(75/487)
Anorectal	11.1	(23/208)	14.8	(60/406)	15.4	(75/487)

^aOne missing indication owing to missing questionnaire data. ^bThree missing experimental indication owing to missing questionnaire data.^cDenominators were adjusted to the number of participants tested at each site (any, urogenital, or rectal). Both tests were missing for seven, of which three had a urogenital test only (all negative) and three had a rectal test only (one was positive).

Table 2. Results of the questions regarding anal sex, symptoms, and sexual behaviour in the past 6 months

Indications	%	n/N
History according to standard guidelines
Anal symptoms	20.0%	(99/495)
Anal sex	28.2%	(140/497)
Anal sex and anal symptoms	5.7%	(28/495)
Total indications for anorectal testing (anal sex or symptoms)	42.5%	(211/497)
Additional sexual history
Anal sex without penetration	47.7% (3.3% condom use)	(236/495)
Anal sex with penetration	21.1% (13.7% condom use)	(104/492)
Anal contact with fingers of partner	38.4%	(189/492)
Anal contact with toys	7.1%	(35/492)
Oral contact with genitals of the woman	72.6%	(358/493)
Oral contact with anus of the woman	18.5%	(91/493)
Resulting experimental indication for anorectal testing (positive answer on any anal contact)	83.3%	(414/497)

n is the total number positive answers for the variable, N is the total number of women who answered that question (excluding the missing answers).

Table 3. Anorectal chlamydia and association with different variables

Variables	n	Rectal CT(%)	Univariate analysisOR (95 %CI)	P value	Multivariate analysisOR (95% CI)	P value
Standard indication for rectal testing	208	(11.1)	0.54 (0.32 to 0.92)	0.023*
Experimental indication for rectal testing	406	(14.8)	0.76 (0.41 to 1.42)	0.40
Anal symptoms	98	(12.2)	0.72 (0.37 to 1.39)	0.35
Anal sex	138	(10.9)	0.59 (0.32 to 1.07)	0.10
Anal sex without penetration	230	(12.6)	0.67 (0.41 to 1.12)	0.13
Anal sex with penetration	103	(7.8)	0.40 (0.19 to 0.86)	0.020*	0.64 (0.28 to 1.47)	0.29
Anal contact with fingers	185	(9.2)	0.43 (0.24 to 0.76)	0.003*	0.58 (0.31 to 1.11)	0.10
Anal contact with toys	34	(5.9)	0.33 (0.08 to 1.42)	0.14
Oral contact with genitals	352	(15.6)	1.09 (0.62 to 1.92)	0.89
Oral contact with anus	91	(7.7)	0.40 (0.18 to 0.91)	0.024*	0.69 (0.29 to 1.66)	0.41
Age, years^a
≤21	104	(30.8)
22–28	220	(14.5)	0.38 (0.22 to 0.67)	0.001*	0.40 (0.23 to 0.71)	0.002*
>28	163	(6.7)	0.16 (0.08 to 0.34)	<0.001*	0.20 (0.09 to 0.41)	<0.001*

^aAge ≤21 years was the reference category. n is the total number positive for the variable, excluding 10 women without a rectal CT test. The rectal CT positive (%) was calculated by excluding women with a missing answer (0–5 per question). Women answering 'don’t know' were added to the 'no' category when calculating odds ratios and Fisher’s exact P values. Significant P values ≤0.05 are indicated by asterisk (*). Only possible risk-factor variables (below the double line) were analysed with logistic regression if significantly associated with rectal CT in the univariate analysis. CT = Chlamydia trachomatis

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