Results

ANTI-HCV SEROPREVALENCE

A total of 4729 samples (98%) were tested for anti-HCV; 96 women declined the offer of testing. Forty eight samples (1.0%; 95% confidence interval (CI) 0.723–1.27%) were HCV IgG seropositive by EIA (fig 1). All women were informed of their result and retested. Ten samples (0.2%) tested negative with the RIBA-3 assay and were considered false positive results. The true prevalence of HCV exposure (antibody positive) was therefore 0.8% (95% CI 0.55–0.1%). Twenty seven patients (0.6%; 95% CI 0.386–0.814%) were viraemic—that is, HCV RNA PCR positive.

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Figure 1

Outcome of testing for hepatitis C virus (HCV) in women with positive antibodies at screening.

Twenty two women (69% of the infected women) were newly identified as HCV infected during their current pregnancy and they were all viraemic.

Discussion

The prevalence of anti-HCV among our multiethnic antenatal population was 0.8%. Our population was derived from an inner city area and it is possible that lower rates of infection may be found in other areas. HCV infection was more common in women of white Caucasian origin, and a history of intravenous drug use was the most predictive risk factor for anti-HCV. However, in 50% of our antenatal patients the history taken by the booking midwife did not identify risk factors for infection. Thus any policy of selective testing of high risk women will fail to identify over half of infected patients. We believe that targeted screening is not appropriate in this setting. The universal offer of HCV testing was acceptable to the local population and the majority of infected women attended for further follow up after delivery. This is in marked contrast with findings in patients referred from sexual health clinics where the majority of patients do not attend for further investigation and treatment.15

Antenatal HCV testing provides an opportunity to identify asymptomatic women with a chronic disease who are likely to benefit from modern therapy with interferon and ribavirin which cures nearly 40% of patients with chronic HCV.16 It is noteworthy that a high proportion of our infected mothers attended for further follow up and treatment, whereas patients with HCV identified in other settings have a high prevalence of subsequent non-attendance. Antenatal screening may therefore identify infected women at a time when they are most receptive to medical intervention. The National Screening Committee Handbook of Population Screening Programmes (National Screening Committee at http://www.open.gov.uk/doh/nsc/nsch.htm) contains detailed criteria that should be met before screening for a condition is initiated. In essence they recommend that a disease should be well characterised and an important health problem for which there is a robust diagnostic assay. Hepatitis C clearly fulfils these criteria. The committee further recommends that there should be an effective therapy for the disease that is more effective in early rather than advanced disease. For infected mothers interferon and ribavirin therapy appears to satisfy these conditions in that there is evidence of reduced efficacy in patients with advanced liver disease (cirrhosis).16 The national committee also recommend that the screening programme should be rigorously assessed in randomised controlled trials to show that screening is effective in reducing mortality and the benefits outweigh the psychological harm caused by the screening procedure. Our study does not address these important issues but data from our questionnaires indicate that the psychological harm from screening is likely to be very small and we believe that large scale randomised controlled trials of screening for HCV in pregnancy should now be considered.

The relatively high false positive rate in our patients (10/48 EIA positive samples were not confirmed on subsequent assays) is a source of some concern and may indicate that pregnant women are more likely to give rise to a false positive test than those who are not pregnant. In general, patients who are RIBA indeterminate are not infected with HCV and are PCR negative. It was therefore surprising to find that one of our patients whose RIBA test was indeterminate was RNA positive by PCR testing. Again, this may indicate that the antibody response in pregnant women may be qualitatively and quantitatively different from those who are not pregnant. Further work is required to clarify this issue but it is important to ensure that all those involved in the screening service are aware of the local false positive rate so that appropriate information can be given to patients.

It is not yet clear if our policy will lead to a reduction in vertical transmission of HCV. Transmission of HCV from mothers to infants is estimated to be 5–10% in mothers who are not coinfected with HIV, and transmission may be enhanced by high viral loads prior to delivery, invasive fetal monitoring, and prolonged labour.17 We speculate that identification of infected mothers will allow their obstetric care to be performed in a way that reduces transmission. Further studies involving large numbers of infected women are required before this is formally proved.

The optimum monitoring and assessment of infants born to HCV infected mothers is not yet clear. Our current policy is to test the children, by PCR, six weeks and three months after delivery. We perform a further PCR test when the child is 14–15 months old and on this occasion we also perform an EIA assay to detect antibodies against HCV. We believe that this “active monitoring” will allow us to identify infected infants at an early age and by establishing links with the hospital will facilitate compliance. This testing policy is under regular audit and review. As infants born to mothers who have one blood borne virus may be at higher risk of contracting hepatitis B, we discuss vaccination against hepatitis B with the parents and we recommend vaccinating the child against this preventable infection. To date, we have identified three infants with perinatal infection and these children are currently undergoing assessment prior to therapy. We do not yet know if early treatment of infected infants will prevent the complications of chronic HCV (chiefly cirrhosis and HCC) but as these complications develop after 25–30 years of infection we believe that early identification and management of infected children will reduce the risk of death in the second and third decades.

Our study shows that pregnant women are willing to be screened for chronic HCV infection and that infected women want to comply with treatment. We believe that our current policy will benefit infected women and we speculate that early diagnosis and intervention for infected children will reduce long term complications although we accept that this has not yet been formally proved.