This is the first study to our knowledge that examines specific hygienic factors associated with HPV concordance in heterosexual couples. Our study is also unique in that it looked at concordance when the female partner had a recent history of incident HPV infection and normal cytology. Although the number of couples was small, we were able to assess detailed histories of specific sexual and hygiene-related behaviors. We believe several of our findings are worth discussion.
To our surprise, we found several relationships between hygienic habits and discordance. Specifically, women who reported sharing a razor or towel with their partners had an increased chance that they would be discordant. This finding appears contradictory to assumptions about HPV transmission; however, very little is actually known about factors that influence HPV detection patterns in couples. We hypothesize that in this case, shared razors and towels pass exfoliated cells infected with HPV DNA from one partner to the other. These exfoliated cells likely come from extra-genital sites (e.g. thighs, pubic hair, etc.) not sampled in the partner. Detection of HPV from the exfoliated cells likely reflects contamination (i.e., the viral DNA is detected because of the infected cellular debris), not an established infection. The detection of HPV from these sloughed cells versus established infections is likely to result in discordance. In this scenario the virus has not entered the subject’s basal cell layer and established active replication, rather the HPV-DNA PCR test detects the HPV DNA from the partner’s squamous cell. The possibility of contamination by HPV passed between partners was underscored by our finding that men who washed their genitals after sex were more likely to be discordant. Cleaning the genital area after sex may reduce the infectivity of men.
Other findings from our study support the notions that cellular debris with HPV infection or rapidly cleared infections have a role in determining concordance in cross-sectional sampling. The shorter time since a couple had sex, the more likely the same HPV type would be found in both partners. This finding is consistent with the trend toward association found by Baken, et al.
] in whose study a shorter number of days since last intercourse was weakly associated with increased chance of anogenital concordance between sexual couples. This suggests that either HPV detected in one partner may be simply a contaminant from the other partner that does not result in prolonged infection or that the natural history of HPV infection in men is different than in women with men clearing infections faster than women [12
The type of sexual activity also appeared to affect concordance. Finger-anal sex in women enhanced anogenital discordance. Our finding may indicate that this particular act results in a higher chance of contamination, and thus discordance, of one of the partners. On the other hand, anal HPV infections, in women particularly, have been shown to clear more rapidly than cervical infections [26
The notion that many HPV-DNA detections are not established infections is underscored by the finding that men who were partners to women with persistent HPV infection were more likely to have HPV detected. Whereas men whose partners did not have persistence of the incident HPV type were unlikely to have HPV detected.
The rate of almost 70% HPV type-specific concordance is higher than rates reported by others when using the same definition of concordance. In Italy, Benevolo et al.
showed a 30.9% concordance rate. In this study couples reported at least 12 months of monogamy and the women had either a current or past history of CIN or HPV [8
]. Baken et al.
found a concordance rate of 37.8% in couples from the United States who were recruited from STD clinic regardless of history of monogamy [1
]. In another study of Dutch couples in which the woman had prevalent CIN lesions and recruited without regard to monogamy 39.8% were concordant [3
]. We believe our higher rate of concordance was partly due to our selection of women with known, recent, incident infection and normal cytology. The higher rate of concordance suggests that HPV may be rapidly transmitted shortly after infection. In contrast, partners of women with CIN, who show lower rates of concordance, may have developed an immune response and cleared the HPV infection by the time the male partner was tested.
Our rate of 8% oral HPV in men and women is similar to pervious studies using oral rinse sampling that reported rates of 5% to 8% [27
] and lower than a study using cytobrushes to sample Finnish spouses which showed a prevalence of 16% in women and 18% in men [30
]. Little comparable data are available for HPV detection in the hand. It is interesting to note in this study, HPV was never found in a person’s palmar area if the anogenital area was negative. This suggests to us that HPV detected in the hand is primarily a contaminant and not an established infection. Future studies should include HPV testing of the hand in order to determine whether it is a meaningful mode of transmission [15
Limitations of this study include a small sample size. We attempted to narrow our search by using restrictive eligibility criteria in order to decrease baseline variability of the subjects and by using an a priori analysis plan using statistical methods appropriate for small sample sizes.
Regardless, reported associations should be considered suggestive and appropriate for consideration in future studies. Although monogamy was part of the eligibility criteria and reported by all participants, we acknowledge that self-reports may not reflect the true rates despite our efforts to ensure confidentiality and privacy to enhance truthfulness. Additionally, we required three months or longer of monogamy. Winer et al.
] found that exposure to a new partner up to eight months prior to HPV sampling was associated with an incident infection. Therefore, the incident infections in the women may have been from contact with other partners beyond the three months. Determination of associations between oral or palmar HPV detection and specific behaviors, such as deep kissing and hand holding, is limited by a lack of information collected.
This study included women with previous HPV exposure. Concordance rates in couples with HPV-naïve female partners may be different since HPV-naïve women will not have developed a cell-mediated immune response to the previously cleared HPV infections. This would result in a longer time of persistence before clearance, thus increasing the chance of concordance. Although we identified incident cervical HPV types in women occurring prior to the couple’s visit, the rate of prior anogenital HPV infections is unknown. A longitudinal study is necessary to examine the role of persistent and latent infections on transmission.
In summary, recent sexual behaviors and hygienic habits show a pattern of association with concordance between sexual partners that suggests HPV-DNA detection on cross-sectional sampling may be due to contamination. The transient nature of recent, incident HPV infections is underscored by the fact that incident HPV types were no longer detected in nearly one-third of the women after eight weeks. Longitudinal studies will be critical to elucidate the apparent importance of transient HPV infections. Our data underscore the importance in examining recent sexual and hygienic behaviors in studies of concordance.