# Chlamydia trachomatis Serology in Women with and without Ovarian Cancer

Authors: Roberta B. Ness; Caixia Shen; Debra Bass; Carlynn Jackson; Kristen Moysich; Robert Edwards; Robert C. Brunham
Journal: Infectious Diseases in Obstetrics and Gynecology
 (2008)

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## Abstract

Pelvic inflammation has been implicated in the genesis of ovarian cancer. We conducted serologic measurements ofChlamydia trachomatis antibodies as a surrogate marker of chlamydial pelvic inflammatory disease.  Women with ovarian cancer (n=521) and population-based controls (n=766) were tested.  IgG antibodies to serovar D of chlamydia elementary bodies (EBs) were detected using an ELISA assay.  The odds of having ovarian cancer among women with the highest titers (≥0.40 OD units) were 0.6 (95% CI 0.4–0.9).  These data do not support our earlier finding of elevated titers for antibodies to C. trachomatis among women with ovarian cancer.


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## Body

## 1. Introduction

Ovarian cancer
is an often fatal disease with an uncertain etiology. We suggested that pelvic
inflammation may play a role in the development of ovarian cancer [1]. PID has been linked to ovarian cancer risk in
some [2, 3] but not all [4] studies. However, PID is poorly recalled in retrospective studies.One quarter to
three quarters of proven cases of PID are caused byNeisseria gonorrhoeae or Chlamydia
trachomatis ascending into the upper genital tract to inflame the
endometrium, tubes, and ovarian epithelium [5]. Of the two pathogens, C.
trachomatis is the most common in American women [6].Chlamydia serology is a relatively specific marker of past chlamydial PID,
particularly of more severe infections [7]. Its sensitivity is not complete; of women with chlamydial PID, about 60%
will have antibodies to C. trachomatis [8] and among women with tubal factor infertility, a similar proportion will
have IgG titers to chlamydia [9].We previously
reported pilot results from a population-based case-control study (117 cases and 170 controls)
of ovarian cancer showing that ovarian cancer was significantly associated with
high IgG antibody titers to chlamydia [10]. The purpose of the present study
was to attempt to replicate this finding in a larger population-based
case-control study of ovarian cancer.


## 2. Materials and Methods

Subjects for this serologic analysis were part of a population-based case-control study
conducted in a contiguous region comprising Western Pennsylvania, Eastern Ohio,
and Southwestern New York State. Cases were residents of this geographic
region with histologically confirmed, primary, epithelial ovarian, fallopian
tube, or peritoneal cancer diagnosed between February 2003 and July 2006. Both invasive and borderline tumors were
included. Women were referred from
hospital tumor registries, clinical practices, or pathology databases and
contacted with the permission of their gynecologists. Eligible
women were at least 25 years of age and within 9 months of initial diagnosis.Controls consisted of women at least age 25 who lived in
telephone exchanges wherein cases resided. Random digit dialing was used to identify age-eligible women, and these
were further screened by the study team to ensure that they had not had a
previous oophorectomy or diagnosis of ovarian cancer. Eligible women were then invited to
participate. Potential controls were frequency matched by 5-year
age group and telephone exchange to cases in an approximately 2:1 ratio.Women were interviewed in their homes by trained interviewers. The questionnaire included a reproductive and
gynecological history, a contraceptive history, a medical history, a family
history, and information on lifestyle practices.We were able to draw blood on 92.5% of the interviewed cases and 84.4% of the interviewed
controls. Blood samples were processed
within 2 hours of collection by a laboratory technician. For this analysis, we selected the first 521
cases and 766 controls with complete questionnaires, tumor registry (e.g.,
histology) information, and adequate serum samples.


### 2.1. Serologic Testing

Serologic testing for IgG antibodies to serovar D ofC. trachomatis elementary bodies (EBs), the extracellular form of the chlamydia
bacteria, was conducted in the reference laboratory of one of the authors (RB)
using an ELISA technique. Final readings are based on a mean of
duplicate runs. All assays were
conducted by personnel masked to case/control status. The intra-assay coefficient of variation for
chlamydia antibodies was 0.06, representing excellent intra-assay
replication. Among masked replicates admixed
into the test set, Pearson correlation coefficients were 0.90 for chlamydia, again
representing excellent interassay variability.


### 2.2. Statistical Analysis

Each of the antibody levels tested was measured in optical density (OD) units (range 0.0–0.4+). We log transformed all OD units to reduce
skewing when considering these as continuous measures and categorized OD units
into neat whole number categories when considering these as discrete
measures. These cut points corresponded
to those in our published pilot study [10]. Odds ratios, with corresponding 95 percent confidence intervals, were
calculated as the primary measure of effect size. Odd ratios were adjusted in unconditional
logistic regression models for any residual effect of age and for family
history of ovarian cancer in any first degree relative (yes/no), tubal ligation
(yes/no), nulliparity versus any parity, years of oral contraception
(continuous), and education (<high school/high school or equivalent/>high
school). In secondary analyses, we
divided serologic titers by quartiles; we also performed secondary analysis limiting our
evaluation to only women with invasive ovarian cancer. We also stratified by age to assess cohort
and age effects. Chlamydial infections typically occur in younger women. Older
women may have time-related diminished antibody titers.


## 2.1. Serologic Testing

Serologic testing for IgG antibodies to serovar D ofC. trachomatis elementary bodies (EBs), the extracellular form of the chlamydia
bacteria, was conducted in the reference laboratory of one of the authors (RB)
using an ELISA technique. Final readings are based on a mean of
duplicate runs. All assays were
conducted by personnel masked to case/control status. The intra-assay coefficient of variation for
chlamydia antibodies was 0.06, representing excellent intra-assay
replication. Among masked replicates admixed
into the test set, Pearson correlation coefficients were 0.90 for chlamydia, again
representing excellent interassay variability.


## 2.2. Statistical Analysis

Each of the antibody levels tested was measured in optical density (OD) units (range 0.0–0.4+). We log transformed all OD units to reduce
skewing when considering these as continuous measures and categorized OD units
into neat whole number categories when considering these as discrete
measures. These cut points corresponded
to those in our published pilot study [10]. Odds ratios, with corresponding 95 percent confidence intervals, were
calculated as the primary measure of effect size. Odd ratios were adjusted in unconditional
logistic regression models for any residual effect of age and for family
history of ovarian cancer in any first degree relative (yes/no), tubal ligation
(yes/no), nulliparity versus any parity, years of oral contraception
(continuous), and education (<high school/high school or equivalent/>high
school). In secondary analyses, we
divided serologic titers by quartiles; we also performed secondary analysis limiting our
evaluation to only women with invasive ovarian cancer. We also stratified by age to assess cohort
and age effects. Chlamydial infections typically occur in younger women. Older
women may have time-related diminished antibody titers.


## 3. Results

About one
quarter of women were younger
than the age of 50 and half
were age 50 to 65 (see Table1). Only about 1% of women reported having PID and 4%
reported having gonorrhea or chlamydia. The well-established protection against
ovarian cancer afforded by oral contraception, pregnancies, and tubal ligation,
and the risk from a family history of ovarian cancer were demonstrated here.Table 1
Frequencies of demographic and reproductive characteristics by case/control status.
VariableCase subjects no. (%)Control subjects no. (%)χ2 (P value)Age group, years24–49135 (25.9)204 (26.6)9.29 (.026)50–56111 (21.3)208 (27.2)57–66129 (24.8)187 (24.4)≥67146 (28.0)167 (21.8)Ethnic groupWhite495 (95.0)736 (96.1)1.14 (.57)Black19 (3.6)20 (2.6)Other7 (1.3)10 (1.3)EducationLess than high school46 (8.8)37 (4.8)13.56 (.001)High school180 (34.5)229 (29.9)Posthigh school295 (56.6)500 (65.3)Family history of ovarian cancerNo487 (95.3)731 (97.3)3.74 (.053)Yes24 (4.7)20 (2.7)Live birthsNone124 (23.8)104 (13.6)22.23 (.000)Any397 (76.2)662 (86.4)Tubal ligationNo389 (78.3)490 (65.0)25.3 (.000)Yes108 (21.7)264 (35.0)Oral Contraception, years0223 (42.8)214 (27.9)40.02 (.000)<1–4205 (39.3)321 (41.9)5–959 (11.3)134 (17.5)≥1034 (6.5)97 (12.7)Menopausal statusPremenopausal142 (30.4)194 (29.9).028 (.87)Postmenopausal325 (69.6)454 (70.1)Self-report PIDNo515 (98.8)759 (99.1).18 (.68)Yes6 (1.2)7 (0.9)Self-report gonococcal or chlamydial cervicitisNo502 (96.4)736 (96.1).062 (.80)Yes19 (3.6)30 (3.9)After adjustment
for possible confounding factors and based on our previous antibody titer cut points
[10], women with ovarian cancer were less likely than controls to have high
chlamydia EB OD unit titers (≥0.40 versus <0.10) (OR 0.6, 95% CI
0.4–0.9; test for trend P=.001) (see Table 2). We then recategorized chlamydia
EB OD units as quartiles based on the distribution of antibody values among
controls (see Table 3). After adjustment
for covariates, the highest quartile of chlamydia EB antibodies was inversely nonsignificantly
associated with ovarian cancer (OR 0.7, 95% confidence interval 0.5–1.1).Table 2
Frequencies and adjusted odds
ratios (ORs) and 95% confidence intervals (CIs) for chlamydial elementary
bodies optical density (OD) units, in cases and controls, categorized by
previously defined cut points. (ORs were adjusted for age, education,
family history of ovarian cancer, tubal ligation, nulliparity/any parity, and
years of oral-contraceptive use).
Chlamydia EBOD unitsCase subjectsControl subjectsOR (95% CI)<0.102483421.00.10–0.1991381731.1 (0.8–1.5)0.20–0.399731130.9 (0.6–1.2)≥0.40621380.6 (0.4–0.9)Table 3
Frequencies and adjusted odds ratios (ORs) and 95%
confidence intervals (CIs) for chlamydial elementary bodies, categorized by
quartiles, in case and control subjects. (ORs were adjusted for age, education, family
history of ovarian cancer, tubal ligation, nulliparity/any parity, and years of
oral-contraceptive use.)
Chlamydia EBEB quartilesCase subjectsControl subjectsOR (95% CI)<0.061331891.00.06–0.111331891.1 (0.8–1.5)0.11–0.241461761.2 (0.9–1.7)≥0.251092120.7 (0.5–1.1)In age-stratified analyses, we continued to find the chlamydia antibodies that reduced
ovarian cancer risk (see Table4). Results were also similar in
analyses limited to invasive ovarian cancer; the risk for ovarian cancer among
women in the highest quartile
of chlamydia EB antibodies versus the lowest was 0.6 (0.4–0.9, test for trend P=.021).Table 4
Frequencies and adjusted odds ratios (ORs) and 95%
confidence intervals (CIs) for chlamydial elementary bodies optical-density
(OD) units, in case and control subjects stratified by age.
OD unitsCase subjectsControl subjectsOR (95% CI)Age 24–49<0.1069821.00.10–0.19932420.9 (0.5–1.6)0.20–0.39918370.6 (0.3–1.1)≥0.4016430.4 (0.2–0.9)Trend = .007Age 50–56<0.10551031.00.10–0.19922470.9 (0.5–1.6)0.20–0.39915201.4 (0.7–3.0)≥0.4019380.9 (0.5–1.8)Trend = .908Age 57–66<0.1058881.00.10–0.19941381.6 (0.9–2.8)0.20–0.39919310.9 (0.5–1.8)≥0.4011300.6 (0.3–1.2)Trend = .227Age ≥67<0.1066691.00.10–0.19943461.0 (0.6 –1.7)0.20–0.39921250.9 (0.4 –1.7)≥0.4016270.6 (0.3 –1.3)Trend = .217


## 4. Discussion

We found that women with ovarian cancer were less likely to have high levels of IgG toC.
trachomatis serovar D EBs. Our data
are inconsistent with our previously published pilot results [10] which showed higher
serologic titers for C. trachomatis among ovarian cancer patients.Our current finding is the reverse of the link between chlamydia and ovarian cancer in our previous
analysis [10]. This is difficult to
explain. The same laboratory conducted
serologic analyses using similar methods for both studies. A population-based case-control method was
used to recruit women into both ovarian cancer case-control studies.Explanations for a lack of association include the long
period between exposure to chlamydia (in the reproductive period) and blood
collection (generally after the age of 50) in our population. If titers fall significantly over time, they
may have become undetectable in some women. Data from a Dutch study suggested that 18% of women had a decline of
twofold in chlamydia titers over four years [11]. However in our own data, over 5–7 years of
followup, women with the highest antibody titers rarely moved to the lowest
tertile over time [12].Another explanation is the lack of sensitivity of antichlamydial antibody serologic testing. Only about 60% of women with PID develop
detectable serology, and the test does not detect gonorrhea, another cause of
PID. This lack of sensitivity would have
resulted in erroneously missing some women with prior PID and would have
resulted in an odds ratio biased toward the null. Moreover, it is  possible that  ovarian cancer itself or
its treatment might acutely reduce chlamydia titers, and therefore mask  an association.Strengths of this study include the population-based ascertainment of cases and controls, the
standardized collection and storage of bloods, the measurement of chlamydia EB antibodies
at a reference, research laboratory, with laboratory personnel masked to
case-control status, and evidence of an independent effect after adjustment for
potentially confounding factors.In summary, our findings do not support previous evidence of a link between chronic persistent
chlamydia infection, the most common cause of PID, and risk for ovarian cancer.



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*Source: 219672-2008-12-18.xml*