Hepatitis C Virus Antibody Screening in a Cohort of Pregnant Women: Identifying Seroprevalence and Risk Factors

Abstract

Objectives:

To describe the prevalence of hepatitis C virus (HCV) antibody, evaluate current risk factors associated with HCV antibody positivity, and identify novel composite risk factors for identification of groups most likely to demonstrate HCV antibody seropositivity in an obstetric population from 2012 to 2015.

Methods:

The Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Maternal–Fetal Medicine Units (MFMU) Network initiated an observational study of mother-to-child transmission of HCV in 2012 that included offering HCV antibody screening to their entire obstetric population. Women presenting for prenatal care prior to 23 weeks gestation without a known multifetal gestation were eligible. For each HCV antibody–positive woman, two HCV antibody–negative women of similar gestational age were identified and included for comparison. Risk factors were evaluated by patient interview and chart review. Cases were identified to have a signal to cutoff ≥ 5 on the Abbott ARCHITECT platform. Ribonucleic acid (RNA) status was evaluated for cases.

Results:

Of 106,842 women screened for HCV antibody, 254 were positive for HCV antibody. Hepatitis C virus antibody seroprevalence rate was 2.4 cases per 1000 women (95% confidence interval (CI): 2.1-2.7). One-hundred thirty-one cases and 251 controls were included in the case-control analysis. Factors associated with HCV antibody positivity included: injection drug use (adjusted odds ratio (aOR), 95% CI: 22.9, 8.2-64.0), blood transfusion (aOR, 95% CI: 3.7, 1.3-10.4), partner with HCV (aOR, 95% CI: 6.3, 1.8-22.6), >3 lifetime sexual partners (aOR, 95% CI: 5.3, 1.4-19.8), and smoking (aOR, 95% CI: 2.4, 1.2-4.6). A composite of any of these potential risk factors provided the highest sensitivity for detecting HCV antibody (75/82 cases or 91%).

Conclusion:

In this cohort, the seroprevalence of HCV antibody was low, and the current risk factors for HCV screening were not identified. These findings may be useful in defining new strategies for identifying mothers with the HCV antibody and the babies susceptible to maternal transmission of HCV.

Clinical Trial Registration:

ClinicalTrials.gov, NCT01959321.

Precis

Screening an unselected obstetric population for hepatitis C virus did not identify a significant population upon which to target intervention.

Introduction

Hepatitis C virus (HCV) infection, with a global prevalence of 2.5%¹,is a chronic disease affecting 2.4 million Americans in 2016.² It has been called a silent epidemic because once infected, many individuals are unrecognized and untreated until years later. Advanced HCV leads to significant morbidities such as cirrhosis, hepatocellular carcinoma, and the need for liver transplant.³

Reported cases of acute HCV infection increased 3.5-fold from 2010 through 2016 (from 850 to 2,967 reported cases, respectively), rising annually.⁴ The increase in acute HCV case reports reflects new infections associated with rising rates of injection-drug use, and, to a lesser extent, improved case detection.^5,6 Several early investigations of newly acquired HCV infections reveal that most occur among young, white persons who inject drugs and live in non-urban areas (particularly in states within the Appalachian, Midwestern, and New England regions of the country)^6,7 . Trends in these states suggest an overall increase in HCV incidence throughout the country.^5,8 The increase in acute HCV infection was a greater increase among young women than among men.⁹ This has led to an increase in the number of infants born to HCV-positive mothers.¹⁰ In the United States, mother-to-child transmission (MTCT) is the primary cause of HCV infection in children, with a MTCT rate in HCV-monoinfected women of 2-8%.^11-14 At least 40,000 children are exposed annually to HCV during pregnancy, resulting in an estimated 2,700 to 4,000 new cases of pediatric HCV infection each year.^15,16,17

The World Health Organization has called for efforts to combat HCV in order to eliminate the disease by 2030¹⁸. Identification of HCV cases is essential to achieving that goal, and special populations such as pregnant women and their infants are of significant interest. At the time of this work, CDC recommendations for screening for HCV were , limited to those deemed to be at risk for HCV regardless of pregnancy status:, outlined in Box 1. Distinct from these risk factors were those for whom HCV screening was of uncertain need, outlined in Box 2¹⁹ (Appendix 2, 2 [http://links.lww.com/xxx])

Box 1: Persons for Whom HCV Testing is Recommended.

• Adults born from 1945 through 1965

• HCV testing is recommended for those who:

  • Currently injecting drugs
  • Ever injected drugs, including those who injected once or a few times many years ago
  • Have certain medical conditions:

    • who received clotting factor concentrates produced before 1987
    • who were ever on long-term hemodialysis
    • with persistently abnormal alanine aminotransferase levels (ALT)
    • who have HIV infection
  • Were prior recipients of transfusions or organ transplants:

    • were notified that they received blood from a donor who later tested positive for HCV infection
    • received a transfusion of blood, blood components, or an organ transplant before July 1992

• Healthcare, emergency medical, and public safety workers after needle sticks, sharps, or mucosal exposures to HCV-positive blood

• Children born to HCV-positive women

Box 2: Persons for whom Routine HCV Testing is of Uncertain Need.

• Recipients of transplanted tissue (e.g. corneal, musculoskeletal, skin, ova, sperm)

• Intranasal cocaine and other non-injecting illegal drugs users

• Persons with a history of tattooing or body piercing

• Persons with a history of multiple sex partners or sexually transmitted diseases

• Long-term steady sex partners of HCV-positive persons

These risk factors are not contemporary (having been in place since 1998²⁰) and there are inherent limitations of risk-factor-based testing. Using well-publicized Centers for Disease Control and Prevention (CDC) and National Institutes of Health (NIH) recommendations for risk-based screening, approximately 50% of patients infected with HCV are detected by risk-factor-based testing and are aware of their disease status.²¹ As risk factor screening has obvious limitations, universal screening in pregnancy has been suggested to allow for linkage to postpartum care and identification of children for future testing and treatment. ^22-25 Universal screening additionally has the advantage of identifying women who may not have contact with health care or health insurance were it not for their pregnancy state.

The American College of Obstetricians and Gynecologists (ACOG) and The Society for Maternal Fetal Medicine (SMFM) have not advocated universal screening for pregnant women for several reasons: this strategy invites the possibility and sequelae of false-positive testing²⁶, mother to child transmission of HCV occurs at a relatively low rate, and there are no effective interventions during pregnancy that would modify mother-to-child transmission of HCV. Additionally, there are no current antiviral treatments approved for use in pregnant women.^27,28 With current systems of care and absence of safety evidence of antivirals during pregnancy, identification of a pregnant woman with HCV does not necessarily expedite treatment. She is not eligible for treatment until she is postpartum, which may be weeks to months, and her baby would not definitively be identified as infected until at least 18 months of life.

As part of an ongoing observational study of mother-to-child transmission of HCV, screening for hepatitis C virus was offered to all pregnant women in the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Maternal–Fetal Medicine Units (MFMU) Network. Our objectives were 1) to describe the prevalence of HCV antibody, regardless of HCV ribonucleic acid (RNA) status; 2) to evaluate current risk factors associated with HCV antibody positivity; and 3) identify composite risk factors for identification of groups most likely to demonstrate HCV antibody seropositivity in an obstetric population screened between 2012 and 2015.

Methods

In 2012, The Eunice Kennedy Shriver NICHD MFMU network initiated an observational study of hepatitis C in pregnancy. A total of 32 hospitals (28 academic, 4 non-academic) located in 14 states participated. Prior to initiation of the observational study, approval by the Institutional Review Boards (IRB) was obtained at all participating hospitals. All women presenting for prenatal care between 2012 through the end of 2015 who were less than 23 weeks gestational age without a known multi-fetal gestation were eligible to be screened for HCV antibody. For all women consenting to the screening test, a blood sample was drawn and sent to a central screening laboratory at the Department of Microbiology at the University Health Network and Mount Sinai Hospital in Toronto, Canada. Women found to be HCV antibody positive, as determined by screening criteria (Appendix 3, available online at http://links.lww.com/xxx), were eligible for the observational study. Patient samples were initially tested by a Chemiluminescent Microparticle Assay on Abbott ARCHITECT platform. Re-testing of HCV antibody positive samples was performed using Ortho Evolis, an Enzyme Immunoassay (Appendix 3, http://links.lww.com/xxx). Cases were defined as those with a signal strength of HCV antibody of the sample compared to the signal strength of the internal cut-off ≥5 (signal to cutoff≥5). Hepatitis C virus antibody–positive women were informed if they qualified for enrollment into the observational study and that their results were for research purposes only.

For the risk-factor assessment, controls were randomly selected from those patients testing negative for HCV antibody based on results from the central screening laboratory. For each case identified, two controls of similar gestational age at the time of screening (± two weeks) at the same participating hospital were eligible. Case and control women who met study eligibility criteria were invited to participate in the observational study. For those who consented for participation into the observational study, socio-demographic, medical and obstetric history, substance abuse, and exposure history were obtained at enrollment (baseline visit) based on patient interview and medical chart review. In addition, women who were enrolled as cases had blood samples collected and tested for HCV RNA at a central virology laboratory at the University of Washington in Seattle, WA. Serum samples collected from enrolled case women who were RNA negative at the baseline visit were further tested by supplemental HCV antibody confirmatory test, the INNO-LIA, a Line Immuno Assay (LIA R) (Fujirebio, Sweden) testing at the Division of Viral Hepatitis Laboratory, Centers for Disease Control and Prevention in Atlanta, GA. INNO-LIA is a recombinant immunoblot assay that is CE-marked with equivalent performance characteristics as the Recombinant Immunoblot Assay (RIBA), no longer available in the United States.

Overall seroprevalence rates were calculated based on the entire cohort of women screened between October 2012 and December 2015 (n=106,842). For descriptive purposes, seroprevalence rates were also calculated by geographic region (Northeast, Midwest, Southeast, Southwest, and West) defined by the location of the hospital where women were screened. Hepatitis C virus antibody seroprevalence rates over time were shown by graphical representation for the three-month moving average. The Cochran-Armitage test for trend was calculated for examination of the trend over time in yearly HCV antibody seroprevalence rates.

Enrolled cases and controls were compared for characteristics based on prior history or present at the baseline examination. The main comparison was between women with HCV antibody signal to cutoff ≥ 5 (n=131) compared with their respective controls. Further, we evaluated two separate subgroups: women who were identified as HCV RNA positive at enrollment (n=88), and women who were unaware of their diagnosis of HCV infection prior to screening (n=82). Each subgroup was compared to their respective controls.

Continuous variables were compared using the Wilcoxon rank-sum test and categorical variables using chi-square or Fisher’s exact test, as appropriate. Crude odds ratios (OR) and 95% confidence intervals (CI) were generated. Adjusted ORs (aOR) and 95% CI were derived using logistic regression analysis with case-control status as the dependent variable and potential risk factors that included any history of drug use (both injected and non-injected), receipt of any blood transfusions, sexual partner with known HCV infection, multiple sexual partners, acupuncture, tattoos, ear and body piercings, incarceration, sexual abuse, cutting or self-mutilation, prostitution, vaginal bleeding, maternal infections during pregnancy (including urinary tract infection or pyelonephritis, pneumonia, syphilis, gonorrhea, Chlamydia, trichomonas vaginalis, bacterial vaginosis, and herpes), and demographic factors that included maternal age, smoking and alcohol use during pregnancy, marital status, race-ethnicity, household income, home ownership status, education level, prior pregnancy, employment status, and type of health insurance modeled as independent variables. Covariates were examined for possible clustering among independent variables using factor analysis methods. Variables exhibiting high within-cluster correlation and low between-cluster correlations were combined and a composite variable comprising the set of variables in the cluster was modeled as an independent variable in the regression analysis. All other covariates were entered separately in the regression model. Potential risk factors and demographic characteristics were examined simultaneously using multivariable logistic regression analysis. A backward proceeding stepwise procedure was used with statistical significance initially set at 0.10. Variables identified from the backward proceeding model and all possible two-way interactions among these variables were further assessed in a reduced model. A final model was generated that included all variables found to be significant based on the intermediate model (P values less than 0.05). Sensitivity, specificity, and the area under the ROC curve (AUC) for HCV antibody seropositivity were calculated based on the significant risk factors both individually and in combination.

No imputation for missing values was performed. Nominal 2-sided P values are reported. Analyses were performed with SAS Version 9.4 (SAS Institute Inc, Cary, NC) and R (http://www.r-project.org/).

Results

A total of 106,842 women were screened for HCV antibody at 32 hospitals in the MFMU network. Two hundred fifty-four women were identified to haveHCV antibody with signal to cutoff ≥ 5 on the Abbott ARCHITECT platform. Among those with available results, the overall HCV antibody seroprevalence was 2.4 cases per 1000 women, (254/106,823; 95% CI: 2.1 - 2.7 cases per 1000 women) in this cohort of pregnant women (Figure 1).

Figure 1.

Hepatitis C virus antibody seroprevalence regardless of enrollment into the observational study, Maternal–Fetal Medicine Units Network, October 2012–December 2015. Hepatitis C virus antibody positive defined as signal to cut–off value at least 5. Number of hospitals: Northeast (n=8), West (n=8), Midwest (n=7), Southwest (n=4), Southeast (n=5).

The geographic distribution of HCV antibody seroprevalance in the screened cohort of women suggested variation by region with noticeably higher rates in the Midwest (0.32%) and Southeast (0.34%), (Appendix 4, available online at http://links.lww.com/xxx). Yearly HCV antibody seroprevalance rates were not found to be significantly different over time in the screened women (p=0.51) (Figure 2).

Figure 2.

Hepatitis C virus antibody seroprevalence over time regardless of enrollment into the observational study, Maternal–Fetal Medicine Units Network, October 2012–December 2015. Hepatitis C virus antibody positive defined as signal to cut–off value at least 5. Squares indicate percentage; bars indicate 95% CI. Includes 3–month interval data from October 2012 through December 2015.

A total of 131 out of 254 cases were eligible for and enrolled into the observational study. There were 51 cases that were not eligible for the observational study and the primary reasons for non-participation into the observational study were refusal of consent (n=31), lost contact (n=25), and unwilling to commit to follow-up (n=16). Women participating in the observational study were similar to the non-participants with respect to HCV antibody level, age, and insurance status.

HCV RNA samples collected at the baseline visit were available for 129 out of 131 enrolled cases. Among the 129 cases, 88 (68%) women were HCV RNA positive (viremic) and 41 (32%) women were HCV RNA negative. Of those identified to be RNA negative, INNO-LIA was indeterminate in 3/39 (8%) women, positive in 32/39 (82%), and negative in 4/39 (10%) women. These INNO-LIA results indicate a false positive rate of 3.1% (4/129) with HCV antibody screening (Figure 1). An extrapolation of the number of HCV RNA positive cases among all women screened would be 173 viremic cases (68% of 254 HCV antibody-positive cases). This would yield an estimated HCV RNA prevalence among all women screened of 1.6 cases per 1000 women (173/106,823).

A total of 131 enrolled women and their respective controls (n=251) were included in the risk factor analysis. Overall, 48% were non-Hispanic white, 25% were Hispanic, 21% were non-Hispanic black, and 5% were other races. Sixty-eight percent had government-assisted insurance or were uninsured, and 49% had an income less than $25,000. Hepatitis C virus antibody–positive women were more likely to be non-Hispanic white, living in a household with parents or other adults, of low socio-economic status (SES), unemployed, government insured, to not have exceeded education beyond 12 years, and to smoke compared with HCV antibody negative women. They were not more likely to have common medical comorbidities of diabetes, hypertension, renal disease, thyroid disorder, autoimmune disease, or seizure disorder (Table 1). In this cohort of HCV antibody positive women, 48 (37%) women were aware of their HCV infection status prior to screening.

Table 1.

Demographic, clinical characteristics, and risk factors of pregnant women screened positive for HCV antibody^* and their controls, MFMU Network, October 2012-December 2015

Characteristic	Controls n=251	Cases* n=131	p
Age (years) (mean ± SD)	28.0 ± 6.1	28.2 ± 5.4	0.58
Race-Ethnicity			0.001
Non-Hispanic white	107 (43.0)	77 (58.8)
Non-Hispanic black	67 (26.9)	14 (10.7)
Hispanic	64 (25.7)	32 (24.4)
Other	11 (4.4)	8 (6.1)
Missing	2	0
Education			0.001
≤ 12 years	96 (38.2)	73 (55.7)
> 12 years	155 (61.8)	58 (44.3)
Employment status			<0.001
Employed	163 (64.9)	55 (42.0)
Unemployed	88 (35.1)	76 (58.0)
Insurance type
Government-assisted	140 (55.8)	104 (79.4)	<0.001
Private	100 (39.8)	23 (17.6)
Self-pay/None	11 (4.4)	4 (3.1)
Annual income			0.02
<$10,000	60 (23.9)	50 (38.2)
$10,000-$24,999	50 (19.9)	28 (21.4)
$25,000-$49,999	40 (15.9)	19 (14.5)
≥$50,000	78 (31.1)	23 (17.6)
Not reported/missing	23 (9.2)	11 (8.4)
Marital Status
Married / living with a partner	163 (64.9)	80 (61.1)	0.46
Never married / other	88 (35.1)	51 (38.9)
Household Status			<0.001
Own	71 (28.4)	17 (13.1)
Rent	133 (53.2)	71 (54.6)
Live with parents/adults	46 (18.4)	42 (32.3)
Missing	1	1
Tobacco use in pregnancy	39 (15.5)	78 (59.5)	<0.001
Alcohol use in pregnancy	19 (7.6)	17 (13.0)	0.09
Maternal birth year			0.55
<1981	55 (21.9)	28 (21.4)
1981-1985	57 (22.7)	32 (24.4)
1986-1990	66 (26.3)	41 (31.3)
>1990	73 (29.1)	30 (22.9)
Current diagnosis of hepatitis B or D†	1 (0.4)	2 (1.5)	0.27
Previous diagnosis of HCV‡	0	49 (37.4)	<0.001
Born to a mother with HCV§	0	8 (6.1)	<0.001
Diabetes	7 (2.8)	4 (3.1)	1.00
Hypertension	14 (5.6)	7 (5.3)	0.92
Renal disease	1 (0.4)	0	1.00
Thyroid disease			0.93
None	237 (94.4)	124 (95.4)
Hypothyroidism	10 (4.0)	4 (3.1)
Hyperthyroidism	4 (1.6)	2 (1.5)
Missing	0	1
Autoimmune disease	5 (2.0)	3 (2.3)	1.00
Seizure	3 (1.2)	6 (4.6)	0.07

HCV, hepatitis C virus; MFMU, Maternal-Fetal Medicine Units; p, p-value; SD, standard deviation.

Data presented as number (percentage) of mothers unless otherwise indicated.

^*HCV antibody positive with signal to cut-off value ≥ 5.

^†Clinical diagnosis of hepatitis B or D in the current pregnancy.

^‡Previous diagnosis of HCV based on medical history (48 were self-identified).

^§Born to a mother with HCV based on medical history.

Of the current risk factors for which the CDC recommends screening for hepatitis C, as outlined in Box 1 (Appendix 2 [http://links.lww.com/xxx]¹⁹), the following risk factors were confirmed in our cohort, in an unadjusted analysis: injection drug use (53% of cases versus 2% of controls, p<0.001) and born to a mother with hepatitis C (6% of cases versus zero controls, p<0.001). No other currently accepted risk factors for hepatitis C were identified in our cohort (e.g., dialysis, HIV, and organ transplant).

When evaluating risk factors currently considered of uncertain need for HCV antibody screening (Box 2) (Appendix 2 [http://links.lww.com/xxx]¹⁹) in an unadjusted analysis, noninjecting illegal drug use, tattoos, multiple piercings, history of multiple sexual partners, a sexual partner with known HCV infection, a history of prostitution, incarceration, and history of sexual abuse or self-mutilation were more likely to be seen in women who were positive for HCV antibody (Table 2).

Table 2.

Comparison of potential HCV risk factors among pregnant women screened positive for HCV antibody^* and their controls, MFMU Network, October 2012-December 2015

Risk factor	Controls n=251	Cases* n=131	Unadjusted		Adjusted (full)†		Adjusted (final)‡
			OR (95% CI)	p	OR (95% CI)	p	OR (95% CI)	p
Injected any drugs	5 (2.0)	69 (52.7)	54.8 (21.2-142)	<0.001	28.4 (7.3-110)	<0.001	22.9 (8.2-64.0)	<0.001
Blood transfusion	10 (4.0)	13 (9.9)	2.7 (1.1-6.2)	0.03	3.3 (0.94-11.4)	0.06	3.7 (1.3-10.4)	0.01
Partners with HCV	4 (1.6)	27 (20.6)	16.0 (5.5-47.0)	<0.001	4.4 (0.98-19.5)	0.05	6.3 (1.8-22.6)	0.005
Sexual partners
1 sexual partner	52 (21.6)	3 (2.5)	1.0		1.0		1.0
2-3 sexual partners	53 (22.0)	14 (11.5)	4.6 (1.2-16.9)	0.02	6.1 (1.3-27.6)	0.02	5.0 (1.2-20.6)	0.03
>3 sexual partners	136 (56.4)	105 (86.1)	13.4 (4.1-44.0)	<0.001	6.3 (1.4-28.5)	0.02	5.3 (1.4-19.8)	0.01
Smoked during pregnancy	39 (15.5)	78 (59.5)	8.0 (4.9-13.0)	<0.001	2.6 (1.0-6.5)	0.04	2.4 (1.2-4.6)	0.009
Used non-injected drugs	91 (36.3)	98 (74.8)	5.2 (3.3-8.4)	<0.001	0.98 (0.45-2.1)	0.96
Acupuncture	14 (5.6)	11 (8.4)	1.6 (0.68-3.5)	0.29	1.3 (0.33-5.1)	0.70
Tattoo	122 (48.6)	103 (78.6)	3.9 (2.4-6.3)	<0.001	1.3 (0.58-3.1)	0.49
Piercings
No piercings	21 (8.4)	3 (2.3)	1.0		1.0
Earlobes piercings only	128 (51.0)	43 (32.8)	2.4 (0.67-8.3)	0.18	1.6 (0.34-7.8)	0.54
Other piercings	102 (40.6)	85 (64.9)	5.8 (1.7-20.2)	0.005	1.9 (0.38-9.3)	0.44
Incarcerated	22 (8.8)	66 (50.4)	10.6 (6.1-18.4)	<0.001	1.6 (0.65-4.1)	0.30
History of trauma/self-harm§	32 (12.7)	46 (35.4)	3.7 (2.2-6.3)	<0.001	0.47 (0.18-1.3)	0.14
Prostitution	3 (1.2)	8 (6.1)	5.4 (1.4-20.6)	0.01	0.11 (0.01-1.6)	0.10
Vaginal bleeding	22 (8.8)	19 (14.5)	1.8 (0.92-3.4)	0.09	1.5 (0.53-4.1)	0.46
Any infections	63 (25.1)	45 (34.4)	1.6 (0.99-2.5)	0.06	1.1 (0.54-2.3)	0.80
Any previous pregnancy	200 (79.7)	103 (78.6)	0.94 (0.56-1.6)	0.81	0.53 (0.23-1.2)	0.14

HCV, hepatitis C virus; MFMU, Maternal-Fetal Medicine Units; OR, odds ratio; CI, confidence interval; p, p-value.

Data presented as number (percentage) of mothers unless otherwise indicated.

^*HCV antibody positive with signal to cut-off value ≥5.

^†Full model included the following covariates: History of injected and non-injected drug use, blood transfusions, sexual partner with HCV, multiple sexual partners, acupuncture, tattoos, ear/body piercings, incarceration, history of trauma/self-harm, prostitution, vaginal bleeding, infections during the current pregnancy, maternal age, smoking during current pregnancy, alcohol use during current pregnancy, marital status, race/ethnicity, prior pregnancy, home ownership, household income, education, employment status, and type of insurance.

^‡Final model included the following covariates: History of injected drug use, blood transfusions, sexual partner with HCV, multiple sexual partners, and smoking during current pregnancy.

^§History of trauma/self-harm includes history of sexual abuse and/or cutting/self-mutilation.

Number of missing values in full model: number of sexual partners (n=19), history of trauma/self-harm (n=1), home ownership (n=2).

In the cluster analysis, history of sexual abuse and self-mutilation were highly correlated (R² = 0.73) and were combined and entered into the model as a single variable denoted as history of trauma or self-harm. All other covariates were entered into the model as individual covariates. In the adjusted analysis, the risk factors that remained associated with HCV antibody seropositivity were: injection drug use, history of blood transfusion, having a heterosexual partner with known HCV infection, smoking during pregnancy, and multiple lifetime sexual partners (Table 2). There were no significant interactions among these variables.

In the subset of viremic women (n=88), injection drug use, history of blood transfusion, having heterosexual partner with known HCV infection, and smoking remained associated with HCV antibody seropositivity (Appendix 5, available online at http://links.lww.com/xxx). In those who were HCV antibody positive and unaware of their status prior to the study (n=82), injection drug use, history of blood transfusion, having a heterosexual partner with known HCV infection, and smoking during pregnancy remained associated with HCV antibody seropositivity (Appendix 6, available online at http://links.lww.com/xxx).

For the subset of women who were unaware of their diagnosis at the time of screening (as well as their associated controls), injection drug use, as an individual risk factor, was associated with a sensitivity of 45%, specificity of 97%, and AUC of 0.71 (95% CI: 0.65-0.77). More than three lifetime sexual partners, considered as an individual risk factor, was associated with a sensitivity of 87%, specificity of 39%, and AUC of 0.63 (95% CI: 0.58-0.68). The combination of risk factors including injection drug use, history of transfusion, known heterosexual partner with HCV infection, smoking in pregnancy, and greater than three lifetime sexual partners demonstrated the highest sensitivity for predicting HCV antibody seropositivity (75/82 cases or 91%), with an AUC of 0.65 (95% CI: 0.60-0.69), (Table 3).

Table 3.

Sensitivity, Specificity, and Area Under the ROC Curve (AUC) for risk factors reported among women screened positive for HCV antibody (excluding patients with known prior HCV diagnosis)^* and their controls, MFMU Network, October 2012-December 2015

Risk Factor(s)	Sensitivity [95% CI]	Specificity [95% CI]	AUC (95% CI)
Individual risk factor:
Injected drugs	37 / 82 (45.1) [34.1 - 56.5]	154 / 159 (96.9) [92.8 - 99.0]	0.71 (0.65 - 0.77)
Blood transfusion	11 / 82 (13.4) [6.9 - 22.7]	153 / 159 (96.2) [92.0 - 98.6]	0.55 (0.51 - 0.59)
Partner with HCV	12 / 82 (14.6) [7.8 - 24.2]	156 / 159 (98.1) [94.6 - 99.6]	0.56 (0.52 - 0.60)
Smoking during pregnancy	50 / 82 (61.0) [49.6 - 71.6]	128 / 159 (80.5) [73.5 - 86.4]	0.71 (0.65 - 0.77)
>3 sexual partners	69 / 79 (87.3) [78.0 - 93.8]	58 / 150 (38.7) [30.8 - 47.0]	0.63 (0.58 - 0.68)
Composite risk factor:
Known risk factors: injected drugs or received blood transfusion	45 / 82 (54.9) [43.5 - 65.9]	148 / 159 (93.1) [88.0 - 96.5]	0.74 (0.68 - 0.80)
Known risk factors or partner with HCV	49 / 82 (59.8) [48.3 - 70.4]	146 / 159 (91.8) [86.4 - 95.6]	0.76 (0.70 - 0.82)
Known risk factors or smoking during pregnancy	58 / 82 (70.7) [59.7 - 80.3]	121 / 159 (76.1) [68.7 - 82.5]	0.73 (0.67 - 0.79)
Known risk factors or >3 sexual partners	74 / 82 (90.2) [81.7 - 95.7]	66 / 159 (41.5) [33.8 - 49.6]	0.66 (0.61 - 0.71)
Known risk factors, partner with HCV, smoking during pregnancy, or >3 sexual partners	75 / 82 (91.5) [83.2 - 96.5]	60 / 159 (37.7) [30.2 - 45.8]	0.65 (0.60 - 0.69)
Known risk factors, partner with HCV, or smoking during pregnancy	60 / 82 (73.2) [62.2 - 82.4]	119 / 159 (74.8) [67.4 - 81.4]	0.74 (0.68 - 0.80)

HCV, hepatitis C virus; MFMU, Maternal-Fetal Medicine Units; AUC, area under the ROC curve; CI, confidence interval.

Numbers within parentheses represent the percentage unless otherwise specified.

^*HCV antibody positive with signal to cut-off value ≥5, excluding forty-nine women with known prior HCV diagnosis.

Number of missing values: number of sexual partners (n=12).

Discussion

In this analysis of pregnant women, the seroprevalence rate of HCV antibody was 2.4 cases per 1000 women (95% CI: 2.1-2.7). Based on data extrapolated from those enrolled, RNA prevalence in this population is suggested to be 1.6 cases per 1000 women. Hepatitis C virus antibody seroprevalence rates remained stable over time for most of the screening period (2012 through 2015). There was evidence of geographic variability with higher rates in the Midwest and Southeast.

We used a standard signal to cutoff ≥ 5 for the HCV antibody case definition in our analysis. Use of this cutoff predicts a true antibody-positive result at least 95% of the time, regardless of the HCV antibody prevalence or characteristics of the population being tested.^{29, 30} In our analysis, this cut-off yielded an RNA positivity rate of 68% (88 out of 129). Furthermore, use of the INNO-LIA recombinant immunoblot assay (supplemental confirmatory testing) among cases with signal to cutoff ≥ 5 on the Abbott ARCHITECT platform with an RNA negative result revealed a low false-positive rate of 3.1% (95% CI: 0.85-7.8), when negative is defined as both RNA and INNO-LIA negative (4 out of 129 samples).

Of the risk factors currently recommended by the CDC as indication for screening of pregnant women for hepatitis C, we confirmed two: injection drug use (current or ever) in 53% of cases versus 2% of controls (p<0.001), and born to a mother with hepatitis C in 6% of cases versus zero controls (p<0.001). This analysis also suggests that screening in concert for, any history of transfusion, known heterosexual partner with HCV infection, smoking in pregnancy, and greater than three sexual partners would identify the greatest number of HCV antibody positive cases (sensitivity, 91%) in this obstetric cohort.

Our results demonstrate that current risk factors could be contemporized, as current risk factor based screening has been in place since 1998²⁰. For the pregnant population, we have demonstrated that the currently accepted risk factors such as exposure to clotting factors, dialysis, and organ transplants are unlikely to be found. A thorough assessment of injection drug use history, smoking, transfusions, number of sexual partners, and partners with HCV infection is more sensitive in an obstetric population. Positive responses for these risk factors are highly predictive of HCV antibody seropositivity in pregnant women, suggesting an alternative to the risk factors currently employed.

We have reported data from the largest cohort of pregnant women to be screened for past or present HCV infection. One could question the generalizability of the MFMU population, but because the MFMU Network now includes both academic and non-academic hospitals throughout the United States, and the study enrolled an ethnically, racially, and socio-economically diverse population, we believe the results to be generalizable. The absence of screening data from 2016 to present may also be considered a limitation given the attention to the opioid epidemic in more recent years. The opioid epidemic is clearly linked to the diagnosis of HCV infection, and in our analysis, there were few risk factors other than injection drug use that were consistently identified to be associated with hepatitis C.⁵ Interestingly, the HCV antibody seroprevalence identified in this study is less than prior studies of pregnant women in the United States (0.75% reported in 1993-1996),³¹ in spite of the current perception of HCV seroprevalence in the midst of the opioid epidemic.

Other limitations include possible selection bias due to our inability to ascertain the number of women who refused screening, as well as, our enrollment of only 65% of HCV antibody positive women eligible for the study (131 out of 203). This participation rate among eligible women reflects the difficulties encountered while engaging HCV antibody positive women for prenatal care. These barriers are likely to be enhanced when engaging this population outside a research setting. Although the participation rate was lower than desired, the HCV antibody positive women who did enroll were similar to those who did not enroll with respect to their antibody level, age, and insurance status.

There is significant interest in updating recommendations for HCV testing in pregnancy, and some have advocated recently for universal screening in pregnancy.^22-25 Improving the identification of women positive for HCV RNA is particularly provocative since available treatments (though not currently approved for use in pregnancy) may cure more than 90% of those with HCV infection.^4,18,32Additionally, the true burden of HCV infection in the pediatric population is limited without identifying all pregnant women with HCV viremia and strategies for improved surveillance in the pediatric population. We acknowledge these benefits, and seek to appropriately include pregnant women in systems of care organized toward eradicating HCV. Our findings suggest that universal screening may not identify a significant HCV antibody positive population upon which to act. And while SMFM and ACOG do not currently recommend universal screening for HCV, both recommend universal screening for substance use disorder³³. Should we become facile in the pursuit of universal screening for substance use disorder, the discussions regarding injection drug use will become more familiar and expected, thus, potentially improving risk-factor-based testing for HCV infection and providing a comprehensive approach to treatment of the pregnant population with HCV. Our analysis suggests that appropriate identification of HCV positive pregnant women may require attention to coexisting substance use disorder. Addressing one without the other may result in suboptimal management of both.

Our results regarding prevalence rates and risk factors of HCV antibody among pregnant women in the United States will be valuable to policymakers as they weigh the costs and benefits of universal screening. At present, cost-effectiveness models suggest the benefit of universal screening. In one study, the strategy is cost effective even at a prevalence rate of 0.07%.³⁴ In another study, models suggest that the strategy is cost-effective unless the prevalence falls below 0.16%.³⁵ If the population studied herein is generalizable, and the population eligible for intervention is 0.16%, it is at least safe to say that controversy remains over the ideal strategy for HCV screening in pregnancy. We acknowledge the landscape and evolution of treatment are changing, and our results may be limited in impact over time. However, in the absence of available treatment for pregnant women, and a small population of pregnant women eligible for treatment, the rationale is weaker for unique, universal hepatitis C screening recommendations for pregnant women.

At present, hepatitis C diagnosis alone in pregnancy does not move toward a cure for HCV; rather, it identifies the need for further maternal and infant evaluation and linkage to care postpartum in a population of women who are difficult to follow. As we seek to appropriately include pregnant women in the efforts to reduce the prevalence of HCV, our analysis does not suggest universal screening to be an optimal strategy at this time. We are called to continue to work collaboratively across such disciplines as obstetrics, pediatrics, infectious disease, gastroenterology, and addiction to appropriately include the unique populations of pregnant women and children into eradication efforts for HCV.