1 Department of Medical Informatics, University of Szeged, 2 Department of Obstetrics and Gynaecology, Semmelweis University, Budapest, Hungary, 3 Institute for International Health, University of Sydney, Australia, 4 National Institute of Oncology, Budapest, 5 Department of Clinical Microbiology and 6 Department of Obstetrics and Gynaecology, University of Szeged, Hungary
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Abstract |
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Key words: cross-sectional study/epidemiology/HPV/prevention/risk factor
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Introduction |
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There is no nationwide registration of HPV in Hungary. In some research centres HPV diagnostic methods have been carried out, but the results are poorly documented.
In order to determine the prevalence and some of the risk factors for persistent cervical HPV infection in asymptomatic women in Hungary a two-centre epidemiological survey was carried out.
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Materials and methods |
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A questionnaire interview was performed during the clinical examination. Questions pertained to the age, occupation, lifestyle, sexual practice, health status, etc. of the patients. Participants had a cervical specimen taken for Papanicolau (Pap) cytology and HPV testing.
HPV hybrid capture assay
Sampling, sample transport and HPV DNA determination were performed according to the assay kit instructions (HPV-HCA, Teva-Biogal RT, Vaci ut, Budapest, Hungary). In each case, sampling for cytological purposes preceded sampling for molecular diagnostics. The sensitivity and specificity of this method are estimated to be 60 and 88% respectively (Deák et al., 2000). Since these are not perfect, Bayes' theorem was applied to estimate the prevalence of the infection. According to Bayes, the probability of disease (P[D+]) can be expressed as follows (Rogan and Gladen, 1978
):
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where P(T+) is the probability of a positive test frequency, P(T+|D+) is the probability of disease given a positive test result (sensitivity), and P(T|D) is the probability of lack of disease given a negative test result (specificity). Bayes' theorem allows a sample-based estimate of prevalence to be corrected for imperfect sensitivity and specificity.
Statistical analysis
The envisaged sample size was calculated using Hsieh's formula (Hsieh, 1989). Assuming a 5% level of significance, a power of 90% and a 10% prevalence of the infection in the population, this resulted in a sample size of 627 women.
Data management was carried out with self-developed software and statistical analyses with the Statistics Package for Social Sciences software package (version 9.0). Statistical methods used were the 2 test including Yates' correction and Student's t-test. To obtain an overview of the risk, the data were cross-tabulated in several ways and multiple logistic regression analysis with dichotomous responses (according to HPV negative or positive results) was performed to differentiate between subgroups with various degrees of high risk. A probability level of P < 0.05 was considered statistically significant.
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Results |
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The difference between the mean ages of the HPV-infected patients (27.8, 95% confidence interval [CI]: 26.529.1 years) and the non-infected women (32.1, 95 CI: 31.332.9 years) was statistically significant (P < 0.001). The results of the univariate unadjusted analysis of risk factors for HPV infection are shown in Table I. The strongest demographic predictors were young age (
24 years) and unmarried family status, which are related to each other. Nevertheless, living in a region where unemployment rate is higher, smoking, having a condyloma, pathological Pap smear and previous gynaecological (cervix, endometrium carcinoma) cancer in the family were all significantly associated with infection.
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Discussion |
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It is necessary to estimate the true prevalence of HPV infection because detection and treatment of asymptomatic cases have a major impact on the incidence of HPV infection, these asymptomatic individuals being an active source of new infections (Kadish et al., 1997; Lacey et al., 1999
). In epidemiology, several methods have been suggested to correct for measurement error. In our analyses, a Bayesian approach was employed for such correction.
This cross-sectional study investigated the associated factors relating to genital HPV. The overall prevalence of positive test HPV cases among 728 women was 20.1%, which corresponds to a corrected estimated infection rate of 16.9%. There were significant differences in the proportions of HPV infection in the different regions. A significantly higher HPV infection rate was identified in the Eastern region of Hungary (27.7%), where an increased rate of unemployment has been observed over the last few years. Additionally, in our survey, women 24 years of age exhibited a particularly high risk of infection. Similar to others, we found that the risk of an abnormal Pap smear increased with persistent HPV infection (Brisson et al., 1994
; Ho et al., 1998
).
The follow-up of HPV-positive cases of our study (unpublished data), in accordance with literature, confirm that the risk of HPV infection can be reduced and the subsequent risk of cervical cancer lowered by a later start of sexual life, a monogamous marriage or permanent relationship and a non-smoking lifestyle (Moscicki et al., 1998).
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Acknowledgements |
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Notes |
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References |
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Submitted on February 1, 2001; accepted on July 9, 2001.