Pelvic inflammatory disease (PID) is a clinical syndrome of the female reproductive
tract characterized by inflammation of the endometrium, fallopian tubes, or peritoneum
(
1
). PID occurs when microorganisms ascend from the vagina or cervix to the fallopian
tubes and other upper genital tract structures (
1
). PID can result from untreated bacterial infections, including chlamydia and gonorrhea,
and can lead to infertility, ectopic pregnancy, and chronic pelvic pain (
1
). Because there is no single diagnostic test for PID, clinicians rely on nonspecific
signs and symptoms for diagnosis. The purpose of these analyses was to assess the
burden of self-reported PID in a nationally representative sample using data from
the National Health and Nutrition Examination Survey (NHANES) 2013–2014 cycle. Starting
in 2013, NHANES female participants aged 18–44 years were asked about a lifetime history
of PID diagnosis. Based on these data, the estimated prevalence of self-reported lifetime
PID was 4.4% in sexually experienced women of reproductive age (18–44 years). The
prevalence of self-reported lifetime PID was highest in women at increased risk, such
as women reporting a previous sexually transmitted infection (STI) diagnosis. Stratified
by race/ethnicity and having a previous STI diagnosis, non-Hispanic black (black)
and non-Hispanic white (white) women reporting a previous STI diagnosis had nearly
equal self-reported lifetime PID prevalence (10.0% versus 10.3%). However, the lifetime
prevalence of PID among black women was 2.2 times that among white women if no previous
STI was diagnosed (6.0% versus 2.7%). These findings suggest that PID is prevalent
and associated with previous STI diagnoses; therefore, it is important for clinicians
to screen female patients for chlamydia and gonorrhea to reduce the incidence of PID.
NHANES is a cross-sectional, complex, multistage survey designed to be nationally
representative of the noninstitutionalized U.S. civilian population (https://www.cdc.gov/nchs/nhanes.htm
). Participants undergo a medical examination and are interviewed in person, during
which time questions regarding sexual and reproductive health are asked. In NHANES
2013–2014, a total of 1,444 women aged 18–44 years were interviewed and had a medical
exam; the response rate was 71.1%. The 1,171 (81%) reproductive-aged female participants
who responded “Yes” to the question, “Have you ever had vaginal, anal, or oral sex?”
were defined as sexually experienced and were the focus of these analyses. Participants
who responded “Yes” to the question, “Have you ever been treated for an infection
in your fallopian tubes, uterus or ovaries, also called a pelvic infection, pelvic
inflammatory disease, or PID?” met the case definition of a lifetime PID diagnosis.
Having received a diagnosis of a previous STI was defined as having had a chlamydia
or gonorrhea infection during the past 12 months or ever having had herpes, human
papillomavirus, or genital warts. The prevalence of self-reported lifetime PID, prevalence
ratios (PRs), and 95% confidence intervals (CIs) were estimated overall and by various
characteristics. Associations were measured by use of the Rao-Scott chi-square test.
All analyses were conducted using SAS statistical software (version 9.3) and accounted
for the complex survey design and sampling weights. As such, these results are nationally
representative. The mobile examination center exam sampling weights were used to weight
the data. Population counts were estimated by multiplying weighted prevalence estimates
by the average of the American Community Survey estimates during 2013–2014.
Among 1,171 sexually experienced reproductive-aged women in NHANES 2013–2014, the
prevalence of self-reported lifetime PID was 4.4% (Table), indicating that approximately
2.5 million women aged 18–44 nationwide have received a diagnosis of PID in their
lifetime (95% CI = 1.8–3.2 million). No significant differences existed in prevalence
of a lifetime PID diagnosis by age, race/ethnicity, or socioeconomic factors, such
as income-poverty ratio, current health insurance coverage, or having a current usual
place for health care.
TABLE
Prevalence of self-reported lifetime pelvic inflammatory disease* among sexually experienced
women† aged 18–44 years (n = 1,171), by selected characteristics — National Health
and Nutrition Examination Survey, United States, 2013–2014.
Characteristic
Sample size no.
Prevalence (%)§ (95% CI)
Prevalence ratio¶ (95% CI)
Total
1,171
4.4 (3.1–5.7)
— (—)
Age group (yrs) (p = 0.28)**
18–24
327
2.9†† (0.8–5.0)
Ref (—)
25–29
185
4.6†† (1.4–7.9)
1.6 (0.6–4.1)
30–34
212
5.0†† (1.8–8.2)
1.7 (0.7–4.3)
35–39
209
3.5 (1.5–5.4)
1.2 (0.5–2.7)
40–44
238
6.7 (2.6–10.8)
2.3 (0.8–6.6)
Race/Ethnicity (p = NC)**
White, non-Hispanic
436
4.4 (2.8–6.0)
Ref (—)
Black, non-Hispanic
245
6.8 (4.0–9.5)
1.5 (0.9–2.5)
Asian, non-Hispanic
130
0.0 (—)
— (—)
Mexican American
195
—§§ (—§§)
—§§ (—§§)
Education level (p = 0.21)**
Less than high school
212
4.3†† (1.0–7.6)
Ref (—)
High school graduate/GED
243
3.1†† (1.1–5.2)
0.7 (0.3–1.8)
Some college/Associates degree
430
6.2 (3.2–9.2)
1.5 (0.6–3.7)
College graduate or above
286
3.0¶¶ (0.4–5.7)
0.7 (0.2–2.9)
Marital status (p = 0.56)**
Married/Living with partner
618
5.0 (2.5–7.6)
Ref (—)
Divorced/Separated/Widowed
120
5.3¶¶ (0.6–9.9)
1.0 (0.4–3.0)
Never married
309
3.5 (1.3–5.8)
0.7 (0.3–1.9)
Income-poverty ratio*** (p = 0.50)**
<150% FPL
500
5.1 (2.9–7.3)
Ref (—)
150%–299% FPL
244
4.7†† (1.0–8.4)
0.9 (0.3–2.5)
≥300% FPL
357
3.2†† (0.9–5.4)
0.6 (0.3–1.5)
Health insurance coverage (p = 0.20)**
Covered
860
4.0 (2.5–5.5)
Ref (—)
Not covered
303
6.1 (2.6–9.6)
1.5 (0.7–3.2)
Has a usual place for health care (p = 0.87)**
Yes
952
4.4 (2.6–6.1)
Ref (—)
No
219
4.7†† (1.2–8.3)
1.1 (0.4–2.9)
Type of place for usual health care (p = NC)**
Doctor's office/HMO
655
3.8 (1.8–5.9)
Ref (—)
Clinic/health center
219
6.0†† (1.2–10.9)
1.6 (0.6–4.2)
Hospital outpatient department/ED
63
—§§ (—§§)
—§§ (—§§)
Age at sexual debut, in years (p = 0.0002)**
≥18
475
2.7 (1.2–4.2)
Ref (—)
16–17
371
4.6 (1.7–7.5)
1.7 (0.7–4.3)
14–15
228
4.9 (2.5–7.4)
1.8 (0.9–3.6)
12–13
79
8.9 (3.3–14.5)
3.4 (1.4–8.5)
<12
18
23.6¶¶ (0.9–46.2)
8.6 (2.7–27.9)
Sexual orientation (p = NC)**
Heterosexual
1,042
4.1 (2.8–5.4)
Ref (—)
Lesbian/Bisexual
102
8.7†† (2.3–15.1)
2.1 (0.9–4.8)
No. male lifetime vaginal sex partners (p = 0.0005)**
1
292
2.5¶¶ (0.1–4.8)
Ref (—)
2–3
230
2.0†† (0.3–3.7)
0.8 (0.3–2.4)
4–9
400
4.1 (2.1–6.0)
1.7 (0.7–4.2)
≥10
249
8.7 (5.0–12.4)
3.6 (1.2–10.7)
Previous STI diagnosis††† (p<0.0001)**
No
978
3.1 (1.9–4.2)
Ref (—)
Yes
193
10.2 (6.0–14.3)
3.3 (1.9–5.7)
Abbreviations: CI = confidence interval; ED = emergency department; FPL = Federal
Poverty Level; GED = General Educational Development certification; HMO = health maintenance
organization; NC = not calculated; STI = sexually transmitted infection.
* Prevalence estimates based on response to the question “Have you ever been treated
for an infection in your fallopian tubes, uterus or ovaries, also called a pelvic
infection, pelvic inflammatory disease, or PID?”
† Based on a response of “Yes” to the question “Have you ever had vaginal, anal, or
oral sex?”
§ Estimates were weighted to be nationally representative of the U.S. population,
accounting for unequal probabilities of selection and nonresponse.
¶ Respondents with missing or unknown values were excluded from prevalence ratio calculations.
** Calculated via use of the Rao-Scott chi-square test. The overall p-values could
not be calculated (p = NC) for some characteristics with zero prevalence in categories
not shown (e.g., “other” category for sexual orientation).
†† Relative standard error >30% but <40%.
§§ Relative standard error >50%; estimates are suppressed.
¶¶ Relative standard error >40% but <50%.
*** Ratio of family income to poverty level as defined by the U.S. Census Bureau.
††† Participants who were told by a doctor or other health care professional in the
last 12 months that they had chlamydia or gonorrhea or were ever told they have herpes,
human papilloma virus, or genital warts.
Significant differences in the prevalence of lifetime PID were observed by the sexual
behaviors and sexual health histories of respondents. The prevalence of self-reported
lifetime PID among women whose age of sexual debut was <12 years was approximately
eight times that of women whose age of sexual debut was ≥18 years (PR = 8.6). Similarly,
the lifetime PID prevalence among women with ≥10 lifetime male vaginal sex partners
was approximately three times that of women with a single partner (PR = 3.6). The
prevalence of lifetime PID was approximately double in women reporting lesbian/bisexual
versus heterosexual orientation (PR = 2.1), and the prevalence among women reporting
a previous STI diagnosis was approximately three times that of women without a previous
STI diagnosis (PR = 3.3).
In stratified analyses (Figure), the prevalence of self-reported lifetime PID among
women reporting a previous STI diagnosis was similar in whites and blacks (10.0% [95%
CI = 4.4–15.6] versus 10.3% [95% CI = 1.3–19.4], p = 0.97). However, among women with
no previous STI diagnosis, the prevalence of self-reported lifetime PID in black women
was 2.2 times the prevalence in white women (black: 6.0% [95% CI: 3.4–8.6] versus
white: 2.7% [95% CI: 1.1–4.4], p = 0.01).
FIGURE
Prevalence of self-reported lifetime pelvic inflammatory disease* among sexually experienced
women† aged 18–44 years (n = 1,171), by race/ethnicity and previous STI diagnosis§,¶
— National Health and Nutrition Examination Survey, United States, 2013–2014
Abbreviation: STI = sexually transmitted infection.
* Prevalence estimates based on response to the question, “Have you ever been treated
for an infection in your fallopian tubes, uterus or ovaries, also called a pelvic
infection, pelvic inflammatory disease, or PID?” Estimates were weighted to be nationally
representative of the U.S. population, accounting for unequal probabilities of selection
and nonresponse.
† Based on a response of “Yes” to the question, “Have you ever had vaginal, anal,
or oral sex?”
§ Participants who were told by a doctor or other health care professional in the
last 12 months that they had chlamydia or gonorrhea or were ever told they have herpes,
human papilloma virus, or genital warts.
¶ Bars indicate 95% confidence interval. Prevalence estimates among non- Hispanic
black women with a previous STI diagnosis have a relative standard error >40% but
<50%.
The figure above is a bar chart showing the prevalence of self-reported lifetime pelvic
inflammatory disease among sexually experienced women aged 18–44 years (n = 1,171),
by race/ethnicity and previous sexually transmitted infection diagnosis, in the United
States during 2013–2014.
Discussion
Based on NHANES 2013–2014 data, an estimated 2.5 million women aged 18–44 years in
the United States reported a lifetime history of PID diagnosis. The increased prevalence
among women reporting a previous STI diagnosis and other behaviors that increase risk
for acquiring an STI underscores the need for STI prevention and control activities.
The higher prevalence among black versus white women without a previous STI diagnosis
suggests that black women might be more likely to have had an undiagnosed, asymptomatic
STI or less likely to have received or reported a diagnosis for a symptomatic infection,
possibly because of decreased access to care (
2
).
PID is not nationally notifiable but is reportable in some states. Few studies have
assessed the incidence of PID using nationally representative data. Estimates from
the National Survey of Family Growth found a similar prevalence of self-reported lifetime
PID treatment among reproductive-aged women (5.7% during 2006–2010) and variations
in self-reported lifetime PID treatment by sexual behaviors (
3
); women with a younger age of sexual debut and a higher number of lifetime vaginal
sex partners were more likely to have received treatment for PID. The results of that
study indicated that black race, having less than a high school education, and an
income <150% of the federal poverty level were associated with receipt of PID treatment.
The findings in this study are subject to at least four limitations. First, small
sample sizes led to unstable estimates and wide CIs. Hence, these results should be
interpreted cautiously. Second, NHANES PID data are based on self-report, an inherent
problem of which is social-desirability bias. Third, given that PID is often asymptomatic
and difficult to diagnose because of the lack of a diagnostic test and the low sensitivity
and specificity associated with the use of a clinical case definition, estimates in
this report might underestimate the actual prevalence of PID. Finally, temporality
could not be established for all factors, and as such, there is no way to know whether
the occurrence of certain factors (i.e., health insurance, access to health care,
previous STI diagnoses) occurred before the PID diagnosis.
PID can result from untreated bacterial infections, including chlamydia and gonorrhea,
both of which are treatable and preventable. Each case of PID results in an estimated
average cost of $3,202 (
4
). Chlamydia and gonorrhea are the most commonly reported STIs in the United States,
with approximately 1.5 million chlamydia and approximately 400,000 gonorrhea infections
reported in 2015 (
5
). Most chlamydia and gonorrhea infections are asymptomatic in women and many go undiagnosed
and untreated (
6
). Results from randomized controlled trials suggest that chlamydia screening is associated
with a decreased incidence of PID (
7
,
8
). The U.S. Preventive Services Task Force recommends that all sexually active women
aged <25 years and older women at increased risk for infection be screened for chlamydia
and gonorrhea (
9
).
Using nationally representative data, this study found a substantial prevalence of
PID in the United States. Lifetime prevalence of PID was highest in women with sexual
behaviors and a sexual health history putting them at increased risk for STIs, including
having had a prior STI diagnosis, and differed by race/ethnicity in those without
a prior STI diagnosis. Given the potential for asymptomatic infections to lead to
PID and the costs associated with treatment, it is important for clinicians to adhere
to U.S. Preventive Services Task Force guidelines for chlamydia and gonorrhea screening
in an effort to decrease the PID burden in sexually experienced women of reproductive
age nationwide (
9
).
Summary
What is already known about this topic?
Pelvic inflammatory disease (PID) has various etiologies, including untreated chlamydia
and gonorrhea infections, and is a potential sequela of these infections, with serious
and costly outcomes. Chlamydia and gonorrhea infections are largely asymptomatic among
women, and as such, most infections are undiagnosed and untreated.
What is added by this report?
In the National Health and Nutrition Examination Survey 2013–2014 cycle, the prevalence
of a self-reported lifetime PID diagnosis was 4.4% among sexually experienced reproductive-aged
women, equating to 2.5 million prevalent PID cases in women aged 18–44 years nationwide.
Prevalence of a self-reported lifetime PID diagnosis varied by sexual behaviors and
sexual health history and differed by race/ethnicity in women without a prior STI
diagnosis.
What are the implications for public health practice?
These findings highlight differences in reproductive health by sexual behaviors and
sexual health history. Given the potential of asymptomatic infection to lead to PID
and the substantial costs associated with treatment, it is important that clinicians
follow chlamydia and gonorrhea screening recommendations for women to decrease the
incidence of PID.