Aim: Our aim was to assess changes in the prevalence of infection with hepatitis C virus (HCV) during the 15-years period with the methodology of repeated cross sectional studies with unlinked anonymous testing of residual sera, obtained from pregnant women in the largest sample of pregnant women ever. To infer about the prevalence of HCV infection and changing of the prevalence among women of reproductive age, the results were compared with the prevalence among female blood donors of the same age.
Objectives and hypotheses: Our objective was to assess the prevalence of HCV infection among Slovenian pregnant women and to describe the changes of this prevalence with repeated cross-sectional studies during the period 1999-2013 and compare the results with the prevalence among Slovenian female blood donors. We tested the following hypotheses: (a) the prevalence of HCV infection among Slovenian pregnant women gradually decreased from 1999 to 2013; (b) the prevalence of HCV infection among Slovenian pregnant women aged 20-29 years in 1999, 2003, 2009 and 2013 was higher than the prevalence among Slovenian blood donors aged 20-29 years.
Justification: There were no data about the prevalence of HCV infection and its change through time in the general population of Slovenia. In many countries, the prevalence of HCV infection was assessed in convenience samples of pregnant women. According to available data, no one has ever assessed the changes of the prevalence among pregnant women.
Methods: We introduced the method of repeated cross-sectional studies to monitor the change in the prevalence of HCV infection with unlinked anonymous testing of residual sera collected for the purpose of screening pregnant women for syphilis. We used sera from the sera bank of the National Institute of Public Health, which were collected in 1999, 2003, 2009 and 2013 within the network of laboratories performing syphilis testing, for the purpose of epidemiological monitoring of the change in the prevalence of HIV infection with unlinked anonymous testing. Samples were tested for anti-HCV. All anti-HCV reactive samples were tested for HCV RNA and genotypes were determined. Descriptive statistical methods were used to describe the prevalence of HCV infection in pregnant women of different ages in those years and results for 20-29 years old pregnant women were compared with prevalence estimates for female blood donors of the same age.
Results: Among the 31,849 tested samples, 41 were anti-HCV positive (0.13 %; 95 % confidence interval (CI): 0.09 % - 0.17 %) and 29 HCV RNA positive (0.09 %; 95% CI: 0.06 % - 0.13 %). The estimates of the annual prevalence of HCV infection (prevalence of HCV RNA) ranged between 0.06 % (95 % CI: 0.02 % - 0.14 %) and 0.14 % (95 % CI: 0.07 % - 0.25 %) (p>0.05). Thus, I did not confirm the hypothesis that the prevalence of HCV infection among Slovenian pregnant women gradually decreased from 1999 to 2013. Also, among the age groups (less than 20 years, 20-29 years and 30 years or more) there were no differences in these years (p>0.05). In 2003, 2009 and 2013, the prevalence of HCV infection among Slovenian blood donors in the age group 20-29 years was 0% (one-sided, 97.5 % CI: 0.00 % - 0.06 %). For these same years, prevalence of HCV infection among Slovenian pregnant women aged 20-29 years was 0.11 % (95% CI: 0.06 % - 0.18 %). I confirmed the hypothesis that the prevalence of HCV infection among Slovenian pregnant women aged 20-29 years in 2003, 2009 and 2013 was higher than the prevalence of HCV infection among female Slovenian blood donors aged 20-29 years.
Discussion and conclusion: Within the largest sample of pregnant women in the world and for the longest monitoring period (15 years), we obtained for the first time ever information about the prevalence of HCV infection among Slovenian pregnant women with the introduction of a new and cost-effective method for epidemiological monitoring with repeated cross-sectional studies with unlinked anonymous testing for HCV infection in easily accessible convenience samples of pregnant women. The estimated prevalence was lower than any previously published estimate of the prevalence of HCV infection among pregnant women in European countries and did not change significantly during this period observed. In Slovenia, oportunistic screening of pregnant women for HCV can not be recommended. Pregnant women constitute a more appropriate group of women of childbearing age to infer about the prevalence of HCV infection and its change among women in the general population than female blood donors of the same age. On the basis of these results, we can conclude that prevalence of HCV infections in the general population of childbearing age is relatively low. I conclude that it would be appropriate to include repeated cross-sectional surveys performed every five years to assess the prevalence of HCV infection in convenience samples of sera collected in convenience samples of pregnant women screened for syphilis into the surveillance of hepatitis C in Slovenia.
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