Our aim was to determine the prevalence and age distribution of low-risk (LR) and high-risk (HR) HPV infection (as well as co-infection with both types) in female population primarily from the Zagreb region (Croatia), as well as to evaluate association of HPV positivity with abnormal cervical cytological findings.
The study involved a total of 422 women (aged 18-67) who approached our outpatient clinic in Zagreb during a 5-year period. Cervical scrapings for the detection of HPV DNA and for cytological evaluation were collected. Digene HC2 HPV DNA test (Qiagen Corporation, USA) was employed in screening specimens for LR and HR HPV types. The cytology was reported using Bethesda system and in accordance to Uniform Classification of Uterine Cervix Cytological Findings in Croatia "Zagreb 2002".
Total HPV prevalence in our study population was 48.10%. Among HPV-positive women, 18.22% were positive for only LR HPV, 62.07% were positive for only HR HPV, whereas 19.70% were positive for both LR and HR HPV. From 2009 to 2013 a continuous rise in HPV prevalence was observed (42.75% in 2009 to 57.14% in 2013); similar (but less linear) trend was seen for HR HPV infection and co-infection with LR and HR HPV, while LR HPV infection has shown pronounced yearly variations. HPV positivity was significantly more prevalent in younger female examinees (18-30 age group) when compared to HPV-negative women (p=0.0122).
Correlation with cervical cytology revealed no statistically significant differences in the frequency of inflammatory changes (p=0.7587), parakeratosis/hyperkeratosis (p=0.5959) and ASC-US (p=0.0997) between HPV-positive and HPV-negative women. Cytologic changes associated with HPV, CIN I (or LSIL) and CIN II/III (or HSIL) were more frequently observed in HPV positive than in HPV negative women (p<0.0001, p<0.0001 and p=0.0001, respectively).
Statistically significant differences within HPV positive groups were found for the category of cytological changes associated with HPV (p=0.0021) and CIN I (p=0.0184); more specifically, both of these cytological classifications were more commonly observed in women co-infected with both LR and HR HPV types than in those solely infected with either LR or HR HPV.
Co-infection with both LR and HR HPV can have a compounding effect in the occurrence of changes associated with HPV and CIN I in Pap smears, as our results have shown that those abnormal cytological findings were more than twice as common in co-infection than in cases of infection with only LR or HR HPV. Hence LR HPV can act as a significant co-factor in the development cytological abnormalities.