This study shows that abnormal anal cytology is a common finding in a diverse population of HIV-infected women and repeated anal cytologic testing increases the likelihood of an abnormal anal cytology diagnosis, resultant referral for HRA, and thus, AIN2-3 diagnosis. Incident anal cytologic abnormalities were detected in 23% of women with a normal baseline anal cytology result. The high rate of incident anal cytologic abnormalities (13.1 per 100 person-years of follow-up) is comparable to the rate found in Durante et al (22 per 100 person-years, 95% C.I. 14–33), from the early HAART era.11
Similar to cervical cytology, the majority of AIN2-3 is diagnosed after a minimally abnormal anal cytology; however, the likelihood of finding AIN2-3 given minimally abnormal cytology is much higher in the anus than in the cervix.16–18
Of 32 participants with a minimally abnormal cytology prior to HRA, 11 (34%) had biopsy proven AIN2-3. Four women with AIN1 on HRA for minimally abnormal anal cytology were diagnosed with AIN2-3 on a second HRA done for a repeat minimally abnormal anal cytology: AIN2-3 diagnosis occurred within one year of initial HRA in three of those four cases. Possible explanations for this difference include rapid disease progression, missed lesion on HRA or discrepancy in pathologic interpretation. While any of these reasons are possible, we had an experienced anoscopist perform every HRA and an experienced pathologist read all pathology results. One limitation of this study is that we did not have an additional blinded pathologist review the results for confirmation. As one-third of the AIN2-3 cases were found after an AIN1 diagnosis and one-third had at least one normal cytology result prior, it appears that there is benefit for repeated screening in at least a subset of individuals. These results will need to be replicated in larger studies.
Several factors were associated with abnormal anal cytology in unadjusted and multivariate analyses. Cervical HR-HPV diagnosis was associated with anal HR-HPV positivity; and trended towards an association with history of STI other than cervical/anal HPV. While it appears that history of STI other than cervical/anal HPV is associated with abnormal anal cytology, the sample size was too small to look at other STIs separately. It would be important to tease out in future studies whether specific STIs are driving this association or whether history of other STI may simply be a marker for history of cervical and/or anal HPV infection. Low CD4 count has been associated with AIN or anal cytology abnormalities in HIV-infected women previously.9,11,13,14
Although only 11 subjects had a current CD4 count less than 200 cells/mm3
, low CD4 count was the strongest predictor of anal cytology abnormality in this population, which highlights the importance of immune reconstitution.
Our plan was for repeated anal cytology and HPV screening every six months over three visits. While a large majority did return for at least one follow-up visit, many subjects had delays in the planned follow-up. While 86% of women with AIN2-3 diagnosed after a second anal cytology result were diagnosed within one year of baseline cytology, we cannot tell from this study whether faster time to AIN2-3 diagnosis made a difference in outcome. In addition, 20% of women in this study diagnosed with abnormal anal cytology during follow-up had ≥one prior normal anal cytology result. While the optimal frequency of anal cancer screening in HIV-infected women remains unclear, it appears that women with risk factors including low CD4 count, and history of anal or cervical HPV or other STIs should undergo repeated cytology screenings regardless of initial normal anal cytology results.
Compliance for our screening visits was good: 87% of subjects in our study were followed for two visits and 71% were followed for three visits—however over 20% of women who were eligible for HRA based on anal cytologic or HPV criteria refused follow-up HRA. Poor compliance with HRA is not unique to our cohort as only 50% of the subjects in the WIHS cohort underwent the recommended HRA.9
It appears from our anecdotal experience that HIV-positive women are more likely to delay or avoid HRA compared to men with HIV and generally express more discomfort with undergoing anoscopy. The HRA visits did not take place in the HIV clinic at the time of this study and the separate HRA location may have been an additional barrier for women who were already uncomfortable about having the procedure. HIV-infected women from this population cited fear of pain or sexual assault flashbacks, embarrassment, and lack of social support as reasons for avoidance of HRA in a recent study (unpublished data). Our patient population is generally covered by Medicaid insurance, therefore cost for the visit was not likely to be a barrier, however additional barriers such as transportation, child care or missing work could all play a role. A better understanding of the reasons for non-adherence with recommended HRA evaluation will be necessary if anal cancer screening is to be adopted as standard of care in HIV-infected women.
While the prevalence of anal cytologic abnormalities at baseline was only 17%, overall, 33% of our subjects had at least one abnormal anal cytology over up to three years of cytologic follow-up. This is comparable to a prevalence
of abnormal anal cytology of 31–38% in other recently reported cohorts of HIV-infected women,9,12,19
and 67–81 % in HIV-infected men who have sex with men.18,20,21
The reasons for the lower rates of abnormal anal cytology in our cohort at baseline are unclear. The patient population at BMC is unusual in that the majority of the study population was born outside of the U.S., acquired HIV through heterosexual contact, and 37% were diagnosed with HIV within the past five years. Our patient population differed from that of the Women’s Interagency HIV Study (WIHS)9
and Study to Understand the Natural History of HIV and AIDS in the Era of Effective Therapy (SUN)12,19
cohorts in several respects: reported history of anal intercourse (WIHS 47%9
vs. SUN 40%19
vs. BMC 22%10
), current cigarette smoking (WIHS 56% vs. SUN 52% vs. BMC 23%), and history of injection drug use (WIHS 34% vs. SUN 3% (within the past six months) vs. BMC 15%). These factors are suggestive of differences in the composition of the patient populations.
In this study of HIV-infected women, anal HPV was detected with HC2 utilizing the residual liquid cervical cytology SurePath specimen. A much lower proportion of participants had detectable prevalent anal HR-HPV infection in our cohort compared with others (16% in BMC versus 44% in WIHS and 84% in SUN). The prevalent cervical HR-HPV infection rates were comparable between the WIHS (19%)9
and BMC (24%)10
cohorts; although much higher in the SUN Study (70%).12
In comparison, rates of anal HPV in HIV-infected men range from 60–95%.18,21–25
Both the WIHS and SUN studies collected the anal HPV specimens in 1cc standard transport media (STM) and used PCR testing whereas in our study, the specimens were the residual from the 10cc liquid cytology specimen (SurePath) (as is routine for detection of high-risk HPV from cervical specimens in the clinical setting). A recent study of anal cancer screening of HIV-positive and negative men utilizing HRA, anal cytology (with PreservCyt, Hologic Inc, Marlborough, MA) and HC2 testing from both STM and liquid residual from cytology found that HC2 had a sensitivity of 91% in detecting AIN2-3 with no difference whether STM versus liquid residual from cytology was used.26
It is unclear if our lower rates of anal HPV detection reflect differences in liquid cytology medium (SurePath vs. ThinPrep), differences in method of HPV detection (HC2 vs. PCR) or a truly lower prevalence of anal HPV in our patient population. In addition, multiple subjects with normal cytology throughout follow-up were transiently HPV positive (). It is unclear if these represent false negative results or if these women were transiently shedding or clearing their infections.
Despite our small sample size, prior abnormal cervical cytology result and history of non-cervical/anal HPV STI were the strongest predictors of AIN2-3 diagnosis in our population. While abnormal cervical cytology tests and STIs are common in HIV-positive women, either diagnosis should likely prompt increased surveillance for AIN2-3. Abnormal anal cytology result appears to be more common in HIV-infected women with AIN2-3 in this population compared to anal HPV positivity; the proportion with anal HPV diagnosis was lower than anticipated and the number of subjects who underwent HRA was too small to say this definitively. While we continue to perform anal HC2 HPV testing on anal cytology samples at our institution, the additive value of HC2 HPV testing in HIV-infected women is less clear from our findings. A large study on HIV-infected women including both HC2 and PCR testing with HRA for all subjects will be necessary to better understand the value of anal HPV testing with HC2 prior to making stronger recommendations for or against its use.
Prior to the adoption of universal screening for anal dysplasia in HIV-infected women, there are several questions that need to be answered. Whether anal cytology is an optimal screening tool for anal cancer and AIN2-3 is not known. Studies to evaluate sensitivity of anal cytology have been conducted in MSM; however, as the disease prevalence is likely much higher in HIV-infected MSM compared with women it is not clear that cytology would be the best screening tool for HIV-infected women. We also do not know the true prevalence of AIN2-3 in HIV-infected women as there have been no studies where all HIV-infected women underwent HRA regardless of cytology results. Lastly, the natural history of anal HPV infections and neoplasia and the efficacy of treatment of AIN2-3 to prevent the development of invasive anal cancer remain unknown.
As HIV-infected women live longer, they continue to be at risk for HPV associated diseases including intraepithelial neoplasia and cancer of the cervix, vulva and anus despite treatment with anti-retroviral therapy. Anal cytology may be a better screening test for AIN2-3 compared with anal HPV testing with HC2 in this population; however repeated anal cytology screening appears necessary for at least a subset of HIV-positive women including those with advanced immunosuppression, history of abnormal cervical cytology, anal and/or cervical HPV or other STIs.