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Keywords:

  • cervical cancer;
  • pap smear;
  • HPV testing;
  • visual inspection with acetic acid;
  • HIV;
  • specificity;
  • sensitivity;
  • Tanzania;
  • Africa

Abstract

  1. Top of page
  2. Abstract
  3. Material and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

The aim of this cross sectional study was to assess type distribution of human papillomavirus (HPV) among HIV positive and HIV negative women who underwent cervical cancer screening, and to examine the ability of visual inspection with acetic acid (VIA), the standard detection method in Tanzania, and HPV-testing to detect cytologically diagnosed high grade lesions or cancer (HSIL+). Women from different areas in Tanzania were invited by public announcement to cervical cancer screening organized by Ocean Road Cancer Institute (Dar-es-Salaam). A total of 3,767 women were enrolled. Women underwent gynecological examination with collection of cervical cells for conventional cytological examination, and swab for HPV-DNA detection (Hybrid-Capture2) and genotyping (LiPAv2 test). Subsequently VIA was performed. The participants were also tested for HIV. HPV16, HPV52 and HPV18 were the three most common HR HPV types among women with HSIL+ cytology with prevalences of 42.9, 35.7 and 28.6%, respectively, in HIV positive women which was higher than among HIV negative women (30.2, 21.9 and 16.7%). A total of 4.5% of the women were VIA positive, and VIA showed a low sensitivity compared to HPV-testing for detection of HSIL+. The sensitivity of VIA varied with staff VIA experience, HIV status and age. Vaccines including HPV16, HPV52 and HPV18 will likely reduce the number of HSIL+ cases independently of HIV status. The frequency of HSIL+ was high among HIV positive women, emphasizing the importance of establishing a screening program which also reaches HIV positive women. Our results highlight the importance of continuous training of staff performing VIA, and also point to the need for other screening methods such as HPV-testing at low cost.

Despite the fact that cervical cancer is potentially preventable through screening and recently through vaccination, an estimated 273,000 women die worldwide every year of this disease.[1] Cervical cancer accounts for 13% of all female cancer[1] and around 80% of cervical cancer related deaths are occurring in low resource countries.[2] In Sub-Saharan Africa, including Tanzania, cervical cancer is the leading cancer-related cause of mortality among women of all age groups.[3] A high prevalence of HPV infection[4] and scarce cervical cancer screening programs are among the main reasons for the high cervical cancer incidence. Moreover, high prevalence of HIV infection in sub Saharan Africa also contributes to a high HPV prevalence and high HPV transmission rate. We have previously reported an HIV prevalence rate among Tanzanian women of 9.3% and being HIV positive was the most important factor associated with genital HPV infection.[5] The HIV-HPV interaction is not entirely understood but a study from Mozambique concluded that the relative importance of HPV types in cervical cancer did not appear to be greatly modified by HIV infection[5] while another recent study conducted in Kenya has indicated that HIV status may alter the spectrum of HPV types in invasive cervical carcinomas.[6]

In high income countries, incidence and mortality due to cervical cancer have been reduced effectively in the past decades with the organized cytology-based screening programs.[7, 8] This decline in incidence is expected to become even more accentuated with the introduction of HPV vaccination among preadolescent girls. HPV-testing have also been implemented in some countries as an additional screening approach allowing to identify more efficiently women who will have an increased risk of high-grade precursor cancer lesions or cervical cancer.

Despite the efficiency of cytology-based techniques, the need for costly cytology laboratories with skilled and highly experienced personnel and the necessity of multiple visits at regular intervals have made pap smears a difficult technique to implement in many low and middle income countries.[9, 10] Therefore, cost effective methods such as visual inspection with acetic acid (VIA) have been adopted in several countries for early detection of precancerous lesions.[11] Also Tanzania has initiated a large cervical cancer awareness campaign in Dar-es-Salaam. Implemented in 2002 first at Ocean Road Cancer Institute, VIA-based and visual inspection with lugol's iodine (VILI)-based cancer detection campaign has subsequently been scaled up to different regions of Tanzania.

The aim of this study was to investigate the HPV type distribution according to cytology result among HIV positive and HIV negative women in Tanzania. Furthermore, it was the aim to assess the sensitivity and specificity of VIA and HPV-testing in relation to cytology—overall and in relation to age and HIV status.

Material and Methods

  1. Top of page
  2. Abstract
  3. Material and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

Enrolment and data collection

The study has been described previously.[5] Briefly, we conducted a cross-sectional study of women in Tanzania. The study was approved by the ethical committee of the Tanzanian National Institute of Medical Research, and all the women who participated in the study were informed orally about the goal of the study and gave informed consent. The study population consisted of two groups of women. The first group included women from an urban area (Dar-es-Salaam region) and a semi-urban region (in North-Eastern and South-Western region from Dar-es-Salaam). The second group was living in rural areas located in the North-Eastern part of Tanzania in Pwani and Mwanza regions, respectively.

In all locations, participants were informed by general public announcement that cervical screening was taking place and they were invited to meet at their nearest hospital or health center for interview and for gynecological examination. All the women were interviewed by qualified female nurses using a structured questionnaire to collect information on socioeconomic factors, lifestyle and reproductive history. The women also underwent a gynecological examination, including a conventional pap smear and collection of cervical cells in sample transport medium (Digene, Gaithersburg, MD) for later HPV-testing. Thereafter, a VIA was performed. The HPV samples were stored at −20°C and shipped at the end of the study to the Department of Experimental Virology (Tuebingen, Germany) for analysis. Finally, a blood sample was obtained for HIV testing if the participant gave consent. HIV testing was voluntary, and women could participate in the study without being HIV-tested. Our project was conducted in parallel with the WHO/IARC initiated demonstration project, where VIA staff training and supervision were an important part. The standard cervical cancer screening method in Tanzania is VIA. In this study, VIA was used as the primary method of detection for neoplasia. However, the results of the cytological examinations were also forwarded and used in the diagnostic follow-up of each individual woman.

Conventional pap smear

During the gynecological examination cervical cells were collected using an Aylesbury wooden spatula (CellPath, Wales, UK) and endocervical brush (CellPath, Wales, UK), smeared on a glass slide and fixed in ethanol. After fixation, slides were air dried and stored in glass slides plastic containers.[12] Cytological analyses were conducted at the Hvidovre University Hospital Pathology Department in Denmark. Laboratory personnel were unaware of any information concerning the study participants. Pap smears results were categorized according to Bethesda classification system 2001[13] and presented in four categories: normal, atypical squamous cells of undetermined significance (ASCUS), low grade squamous intraepithelial lesion (LSIL), and high grade squamous intraepithelial lesion or cancer (HSIL+).

Visual inspection with acetic acid

A World Health Organization (WHO/IARC) demonstration project “prevention of cervical cancer through screening using visual inspection with acetic acid (VIA)” was conducted in 2005–2009 involving seven six African countries, including Tanzania local training was conducted at each site participating in the project, by clinicians who were experienced in VIA and cryotherapy. Supportive supervision and refresher training was conducted at regular intervals by the country project coordinators.[14]

In our study, the cervical cancer screening program was first initiated in Dar-es-Salaam at Ocean Road Cancer Institute (ORCI) and subsequently extended to hospitals and health centers at districts level. In each new location, at least two health care personal had attended a cervical cancer training program organized by ORCI/IARC within the past 12 months.

VIA was performed after the collection of cervical cells for cytology and HPV DNA detection. A 5% acetic acid solution was applied on the cervix using a cotton-tipped swab. The VIA result was considered positive when well-defined distinct aceto-white areas appeared close to the squamocolumnar junction within 1 min after acetic acid solution application.[15, 16] Subsequently, following the standard procedures in Tanzania,[17] VIA positive women were either asked to come back for a follow up at the latest 3 months later or referred immediately to the nearest hospital for further diagnosis and treatment according to the extend of VIA positive lesions and their suspected severity.

HPV DNA analysis

The testing method for the presence of HR HPV DNA in cervical cell swabs has been described previously in detail.[18] Briefly, cervical cell swabs were collected using Hybrid Capture 2 (HC2; Digene, Gaithersburg, MD) kit brushes, and the tubes were frozen at −20°C in PreservCyt fixative and sent in Germany (Department of Experimental Virology, Universitaetsklinikum, Tuebingen) for analysis. Laboratory personnel were unaware of the cytology, the VIA results and the information collected by questionnaire. The specimens were tested for the presence of HPV using the HR HPV detecting probes. Samples which were positives were further analyzed in order to determine the HPV genotypes (LiPA; Innogenetics, Gent, Belgium).

The HC2 HR HPV probe enables the detection of at least 13 HR HPV types namely 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 68.[19] We used the United States Food and Drug Administration-approved threshold of 1.0 pg HPV DNA/ml, which corresponds to 1.0 relative light unit coefficient (RLU/CO).

Genotyping was performed on 200 µl of the remaining denatured product from the HC2 test. DNA was isolated using the MagnaPure device (Roche Systems, Indianapolis, IN). Subsequently, 5 µl of DNA solution was used for the LiPAV2 SPF-PCR assay in the final volume of 50 µl using AmpliTAq gold and submitted to PCR rounds. PCR products were then denatured and a 10 µl aliquot hybridized to a HPV genotype detection strip. The resulting strip reading was performed using a scanner the LiRAS prototype software (Innogenetics).

HIV testing

HIV testing was done locally in Tanzania. Blood specimens were tested according to an algorithm that included one rapid immunoassay SD Bioline HIV-1/2 3.0 rapid test (Standard Diagnostics, South Korea). When positive for anti-HIV antibodies, samples were assessed with immunological test Determine HIV-1/2 (Abbott Laboratories, South Africa) and subsequently with a third rapid test (UNIGold method/Recombigen®HIV; Trinity Biotech, USA) in case results obtained from the first two tests were conflicting with each other. Finally, the results were given to each woman individually and confidentially. When tested, women were provided pre- and post-HIV test counseling dispensed by a trained nurse. Women who were positive were referred to a care and treatment clinic (CTC) for HIV infection stage assessment, treatment and progression follow-up.

Statistical analysis

The prevalences of the different cytology results, overall and in relation to HIV status were estimated according to age ([<25, 25–29, 30–34, 35–39, 40–49, 50–59 and ≥60 years] or [<25, 25–29, 30–34, 35–39, 40–49 and ≥50 years], respectively). The overall HPV prevalence and type-specific HPV prevalence were estimated for all women, and were also estimated by HIV status (positive, negative) and cytology result (normal, ASCUS, LSIL, and HSIL+). HPV types were grouped in species based on the analysis of the genital HPV types.[20]

We also estimated the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of VIA and of HR HPV-testing for the detection of HSIL+ compared to cytology as gold standard. This was done for all women and according to HIV status, age (<29 and ≥29 years old) and according to site of residence (urban, rural) with 95% confidence interval. Statistical analyses were carried out using the SAS software, version 9.1.

Results

  1. Top of page
  2. Abstract
  3. Material and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

A total of 3,767 women were included in the prevention of cervical cancer in Tanzania (PROTECT) study. Thirty-seven women were excluded because clinical conditions prevented proper examination (e.g. hysterectomy, menstruation, pregnancy). Subsequently, we excluded 31 women because of incomplete data on HPV (empty tubes or too little cell material) leaving 3,699 women. For this study, an additional 96 women (2.6%) were excluded because their cervical sample was inadequate for cytological examination, leaving 3,603 women for analysis. The study population consisted of 1,828 women from urban areas and 1,775 women living in rural areas. A total of 884 (24.4%) were 29 years or younger, 1,263 (35.1%) 30–39 years, 907 (25.2%) were 40–49 years old and 549 women (15.3%) were 50 years or older. Finally, 334 women (9.3%) tested HIV positive, 3,005 (83.4%) were HIV negative and 264 (7.3%) were not tested for HIV.

Cytology according to age and HIV status

A total of 3,235 women (89.8%) had normal cytology, 169 women (4.7%) had ASCUS, 62 (1.7%) had LSIL, and 137 women (3.8%) had a cytological diagnosis of HSIL+. The mean age of women with ASCUS was 39.6 years (range 18–77 years), women with LSIL had a mean age of 33.7 years (range 22–51 years) while the mean age of women with HSIL+ was 43.4 years (range 22–80 years). In Figure 1a, prevalence of the different categories of abnormal cytology is presented according to age. The prevalence of ASCUS was stable around 4% until the age of 40 years and then increased in older women (Fig. 1a). In contrast, LSIL decreased with increasing age. The prevalence of a cytological diagnosis of HSIL+ increased with increasing age, the prevalence being 1.2% in women below 25 years old whereas this applied to 12.9% of women 60 years or older. This increase was seen both among HIV negative and HIV positive women (Fig. 1b). The prevalence of HSIL+ was higher among HIV positive women (8.4%) compared to HIV negative women (3.2%). In HIV positive women, the prevalence of HSIL+ was 4.2% in the youngest age group increasing to 15.4% among women 50 years or older. Among HIV negative women 50 years or older, 6.6% had HSIL+ cytology.

image

Figure 1. Age-specific prevalence of abnormal cytology results among all women (N=3603) (a) and age-specific prevalence of HSIL+cytology results (b) according to HIV status.

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HR HPV type distribution in relation to cytology and HIV status

Overall, women with ASCUS, LSIL and HSIL+ had a HR HPV prevalence of 41.4, 77.4 and 94.2%, respectively. In Table 1, the corresponding prevalences are shown according to HIV status. Among HIV positive women, 66.7, 100 and 100% of the women, respectively, with ASCUS, LSIL and HSIL+ were HR HPV positive. In comparison, this applied to 37.1, 67.5 and 92.7% of HIV negative women with ASCUS, LSIL and HSIL+, respectively. Also among women with normal cytology, we found a significantly higher HPV prevalence among HIV positive women (35.9%) compared to HIV negative women (12.8%) (Table 1).

Table 1. HR HPV type distribution among normal and abnormal Pap smears results of HIV positive women(N=334) and HIV negative (N=3005)
 HIV positiveHIV negative
Normal (N=265)ASCUS (N=24)LSIL (N=17)HSIL+ (N=28)Normal (N=2737)ASCUS (N=132)LSIL (N=40)HSIL+ (N=96)
N(%) All(%) among HPV+N(%) All(%) among HPV+N(%) All(%) among HPV+N(%) All(%) among HPV+N(%) All(%) among HPV+N(%) All(%) among HPV+N(%) All(%) among HPV+N(%) All(%) among HPV+
HRHPV95(35.9)(100)16(66.7)(100)17(100)(100)28(100)(100)351(12.8)(100)49(37.1)(100)27(6.75)(100)89(92.7)(100)
Alpha 9                        
HPV 1614(5.3)(14.7)4(16.7)(25.0)1(5.9)(5.9)12(42.9)(42.9)48(1.8)(13.7)10(7.6)(20.41)5(12.5)(18.51)29(30.2)(32,61)
HPV 317(2.6)(7.4)00 020(0.7)(5.7)6(4.6)(12.21)2(5.0)(7.41)3(3.1)(3.41)
HPV 335(1.9)(5.3)01(5.9)(5.9)1(3.6)(3.6)15(0.6)(4.3)4(3.0)(8.2)1(2.5)(3.7)9(9.4)(10.1)
HPV 3513(4.9)(13.7)3(12.5)(18.8)3(17.7)(17.6)3(10.7)(10.7)48(1.8)(13.7)5(3.8)(10.2)5(12.5)(18.5)13(13.5)(14.6)
HPV 5220(7.6)(21.1)5(20.8)(31.3)5(29.4)(29.4)10(35.7)(35.7)74(2.7)(21.1)7(5.3)(14.3)4(10.0)(14.8)21(21.9)(23.6)
HPV 587(2.6)(7.4)0  1(5.9)(5.9)011(0.4)(3.1)5(3.8)(10.2)4(10.0)(14.8)6(6.3)(6.7)
Alpha 7                        
HPV 1810(3.8)(10.5)2(8.3)(12.5)1(5.9)(5.9)8(28.6)(28.6)28(1.0)(8.0)6(4.6)(12.21)2(5.0)(7.41)16(16.7)(18.01)
HPV 393(1.1)(3.2)1(4.2)(6.3)1(5.9)(5.9)014(0.5)(40)03(7.5)(111)2(2.1)(2.2)
HPV 454(1.5)(4.2)01(5.9)(5.9)1(3.6)(3.6)18(0.7)(5.1)1(0.8)(2.01)1(2.5)(3.7)4(4.2)(45)
HPV 59001(5.9)(5.9)01(0.04)(0.3)00 0  
HPV 688(3.0)(8.4)02(11.8)(11.8)025(0.9)(7.1)1(0.8)(2.0)0 2(2.1)(2.2)
Alpha 5                        
HPV 5115(5.7)(15.8)4(16.7)(25.0)5(29.4)(29.4)1(3.6)(3.6)51(1.9)(14.5)7(5.3)(14.3)3(7.5)(11.1)7(7.3)(7.9)
HPV 823(1.3)(3.2)2(8.3)(12.5)0  2(7.1)(7.1)7(0.3)(2.0)01(2.5)(3.7)3(3.1)(3.4)
Alpha 6                        
HPV 533(1.1)(3.2)1(4.2)(6.3)02(7.1)(7.1)14(0.5)(4.01)2(1.5)(4.11)4(10.0)(14.81)2(2.1)(2,21)
HPV 569(3.41(9.5)03(117.7)(17.6)1(3.6)(36)19(0.7)(5.4)1(0.81(2.0)2(5.0)(7.4)3(31)(3.4)
HPV 6614(5.3)(14.7)3(12.5)(18.8)2(11.8)(11.8)4(14.3)(14.3)35(1.3)(10.0)2(1.5)(4.1)2(5.0)(7.4)9(9.4)(10.1)
Multiple                        
HPV types38(14.3)(40.0)8(33.3)(50.0)7(41.2)(41.2)12(42.9)(42.9)99(3.6)(28.2)11(8.3)(22.4)12(30.0)(44.4)27(28.1)(30.3)

Table 1 also shows the HR HPV type distribution by cytological diagnosis and HIV status. HPV16, HPV52 and HPV18 were the three most common HR HPV types among women with HSIL+ cytology results with prevalences of 42.9, 35.7 and 28.6%, respectively, in women who were HIV positive compared to HIV negative women where the corresponding prevalences were 30.2, 21.9 and 16.7%. Both among HIV positive and HIV negative women, HPV16 and 18 were the only types where an increasing gradient in the prevalence was seen from normal cytology to HSIL+. For HPV52 this was only seen in HIV positive women. Finally, multiple infections were more common among HIV positive women compared to HIV negative across all cytological categories and among HIV positive, 42.9% of women with HSIL+ had a multiple HPV infection compared to 28.1% women among HIV negative women (Table 1).

Performance of VIA and HR HPV-testing with cytology as gold standard

A total of 161 women (4.5%) were VIA positive. The prevalence of VIA positivity was significantly higher among HIV positive women (12.9%; 95% CI: 9.3–16.5) than in HIV negative women (3.4%; 95% CI: 2.8–4.0). Among the 161 VIA positive women in the study, 70.8% had normal cytology, 24.2% had an HSIL+ diagnosis and 5% had ASCUS/LSIL (Fig. 2a). Furthermore, among women who were VIA positive but had normal cytology, 83.3% were HR HPV negative. The majority of women were VIA negative and 90.7% also had normal cytology. However, a total of 98 women had HSIL+ and 223 women had ASCUS/LSIL lesions on cytology. Among the 98 women with negative VIA and HSIL+ cytology, 93% were HR HPV positive.

image

Figure 2. Overview of women's cytology results distribution according to VIA results (a) and cytology results distribution according to HR HPV results (b).

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HPV-testing showed that 725 women (20.2%) were HR HPV positive (Fig. 2b). Of these, 478, 118 and 129 women (65.9, 16.3 and 17.8%), respectively, had a normal cytology, ASCUS/LSIL and HSIL+. In addition, among 129 women who tested HR HPV positive and had HSIL+ on cytology, still 91 (70.5%) were VIA negative. Among women who were HR HPV negative, the majority (95.8%) had a normal cytology results while 3.9 and 0.3%, respectively, had an ASCUS/LSIL or HSIL+ diagnosis.

In Table 2, the sensitivity and specificity of VIA and HPV-testing for the detection of HSIL+ cases are shown (i.e. cytology as gold standard). Among all women, VIA had a sensitivity of 28.5% (95% CI: 20.9–36.0) and a specificity of 96.5% (95% CI: 95.9–97.1). The sensitivity for VIA was higher in women from urban areas (39.0%) and among HIV positive women (50.0%). HPV-testing had a high sensitivity (94.2%; 95% CI: 90.2–98.1) and a somewhat lower specificity (82.8%; 95% CI: 81.6–84.1). The sensitivity of HPV-testing did not differ according to area of residence. The specificity was lowest among HIV positive women (58.2%) and among women 29 years or younger (74.7%). The VIA and HPV-testing had a PPV ranging from 16.7 to 32.6% and from 7.2 to 22.9%, respectively. For both VIA and HPV-testing, the lowest PPV was seen among women below 29 years old. NPV was high for both VIA and HPV-testing (>99.6%) and reached up to 100% for HPV testing among women who were below 29 years and among women who were HIV positive.

Table 2. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of VIA and HR HPV-testing to detect cytologically confirmed HSIL+lesions among all women, and stratified by age, residence and HIV-status
  VIAHR HPV
 NScreen positive (%)Sensitivity %(95%CI)Specificity %(95% CI)PPVb %NPVc %Screen positive (%)Sensitivity %(95% CI)Specificity %(95% CI)PPVb %NPVc %
  1. a

    Women who refused HIV testing were not included in the table

  2. b

    PPV: Positive Predictive Value

  3. c

    NPV :Negative Predictive Value

All women36034.528.5(20.9–36.0)96.5(95.9–97.1)24.297.220.194.2(90.2–98.1)82.8(81.6–84.1)17.899.7
Age               
<29884 27194.135.3 27.5(12.6–58.0)96.5(95.3–97.8)16.799.126.7100.0(88.9–97.8)74.7(71.9–77.6)7.2100.0
>29 4.6 (19.5–35.5)96.5(95.8–97.2)26.496.618.093.3 85.5(84.1–86.9)22.999.6
Site of Residence               
Urban18285.539.0(26.5–51.4)95.6(94.6–96.6)22.897.916.993.2(86.8–99.6)85.6(84.0–87.3)17.899.7
Rural17753.420.5(11.6–29.5)97.4(96.7–98.2)26.796.423.494.9(90.0–99.8)79.8(77.9–81.8)17.899.7
HIV statusa               
HIV positive33412.950.0(31.5–68.5)90.5(87.2–93.8)32.695.246.7100.058.2(52.6–63.7)17.9100.0
HIV negative30053.422.9(14.5–31.3)97.2(96.7–97.8)21.697.517.292.7(87.5–97.9)85.3(84.0–86.6)17.299.7

Discussion

  1. Top of page
  2. Abstract
  3. Material and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

We find that the prevalence of a cytological diagnosis of HSIL+ is higher in HIV positive women than in HIV negative women and this applied to all age groups, the prevalence being as high as 15.4% among HIV positive women 50 years or older. Likewise, the prevalence of VIA positivity was considerably higher in HIV positive women than in HIV negative women. This result is in line with a study from Côte d'Ivoire[21] where the VIA positivity prevalence was similar to our study, whereas other studies from Sub-Saharan Africa found higher prevalences.[22-24] This high risk among HIV positive women is also reflected in a higher prevalence of HR HPV in women with normal cytology (35.9%) compared to HIV negative women (12.8%). Altogether, these findings underline the urgent need for implementation of cervical cancer screening in HIV clinics.

Overall, the most frequent HPV types both in HIV positive and HIV negative women were HPV52, HPV51 and HPV16, but HPV66, HPV35 and HPV18 were also common. Looking at the type-distribution in relation to HIV status and cytology result, we find that independently of HIV status HPV52 was the commonest type in women with normal cytology whereas among women with HSIL+ HPV16 was the most frequent type. This is in line with a recent meta-analysis of studies in five continents of the HPV prevalence in women with normal cytology showing that HPV52 is particularly common in Africa.[25] In our study, HPV16 and 18 were the only types where the prevalence increased with severity of the cytology diagnosis both among HIV positive and HIV negative women. Prophylactic HPV vaccines will likely be able to reduce HSIL+ cytology cases independently of HIV status. These findings are in line with another study in East Africa.[26] In our study, only three women in the HSIL+ group had cancer on the study cytology sample. It is known that the distribution of HPV types is different in precursor lesions compared with cancers with HPV16 and 18 being more dominant in cancers than in precursor lesions.[27]

We compared the ability of VIA and HR HPV-testing to identify women with a cytological diagnosis of HSIL+. We showed that the performance of VIA was not optimal since 98 out of a total of 137 HSIL+ lesions were missed. If a woman is screened once or twice in a lifetime, the sensitivity should be considerably higher. The majority of VIA positive women had a normal cytology diagnosis. Among VIA positive women, only 24.2% had HSIL+ on cytology. Altogether this resulted in a low sensitivity for the VIA method. This is in line with some previous studies assessing the sensitivity and specificity of VIA for the detection of CIN3+,[28] and a recent randomized trials,[29] but it is lower than in some other studies[22] and meta-analyses.[30] In our study, we had a relatively low prevalence of cervical abnormalities and this could also be part of the explanation for the low sensitivity of VIA.

Furthermore, the interpretation of VIA has been shown to vary according to the experience of the investigator. Vedantham et al. showed that when performed by different gynecologists, VIA positivity rate ranged from 4 to 31%.[31] This study was made in different settings (both health centers and hospital) relying on changing staff with varying experience and knowledge in VIA interpretation. A cross sectional study conducted at Ocean Road Cancer Institute (Dar-es-Salaam, Tanzania) between 2002 and 2007, showed that VIA performance fluctuated throughout the screening period and with best performances occurring just after training/retraining periods.[22] In this study, the staff had received both theoretical and practical training in cervical cancer screening methods, however several screening teams with different accumulated experience were involved in the study and therefore it cannot be ruled out that this could partly explain the difference in sensitivity of VIA in urban (39.0%) and rural settings (20.5%). In this study, the cytology results were forwarded to the screening team in Tanzania and were used for further follow-up and treatment of the women when necessary.

Finally, patient-related factors such as age and presence of vaginal infections have also been shown to have an influence on reading of VIA results by transforming cervix aspect and coloration possibly leading to misinterpretation.[32, 33] We showed that VIA had a better sensitivity among women ≤29 years. The quality of VIA interpretation and its correlation with the other techniques used also varied according to HIV status and we showed that the VIA method performed better when used among HIV infected women as it has been showed in other studies.[34] The higher sensitivity in HIV positive women can be explained if the cervical lesions constitute a larger surface of the cervix.

We showed that HPV-testing had a very good sensitivity for detection of HSIL+. Although sensitivities were the highest (100%) among HIV positive women and among women ≤29 years, HPV-testing performed consistently well across HIV status, age or site of residence stratification varying from 92.7 to 100%. On the other hand, the specificity of HPV-testing was not optimal and was lowest among HIV positive and among women ≤29 years and HPV-testing had a poorer specificity compared to VIA for the detection of cervical cell changes principally due to the fact that HPV-testing cannot distinguish between transient and permanent infections.[35] The findings of this study could indicate that HPV testing would be a better primary screening tool for cervical cancer in Sub-Saharan Africa, possibly with VIA as a secondary tool to increase specificity. However, it has been suggested that even though VIA has several limitations, implementation of this modality in low-resource settings may be a first step in establishing an infrastructure that may facilitate a future implementation of a cheap and easy to handle HPV detection method.[36]

The relatively large sample size and the ability to stratify on HIV status are strength of this study. However, it is a limitation that we did not have histological results and thus our case definition (gold standard) was based on a cytological diagnosis of HSIL+. This makes our results not entirely comparable with studies based on histologically verified cases of CIN2/3 and they should consequently be interpreted with caution. Another study from Tanzania that had histology results to evaluate VIA, found a sensitivity of VIA to detect CIN2–3 lesions of 60.6%.[20] Beside a histological diagnosis, a full evaluation of the value of different screening modalities would demand an assessment of the follow-up procedures and program effectiveness as loss to follow-up of screen-positive women is an important concern in cervical cancer screening programs. Furthermore, even though this study has a large sample size, the number of HSIL+ cases is still relatively limited, especially after stratification according to HIV status.

In conclusion, we showed that HPV16, HPV52 and HPV18 were the most prevalent types among Tanzanian women with a diagnosis of HSIL+ with no major differences between HIV positive and HIV negative women. The prevalence of HSIL+ was as high as 8.4% among HIV positive women, emphasizing the importance of establishing a screening program which also reaches HIV positive women. VIA had a low sensitivity for the detection of HSIL+ but a good specificity. The interpretation of VIA is not objective and is strongly associated with the experience of the operator. However, despite the drawbacks of VIA it still constitutes a valuable instrument in cervical cancer screening and the infrastructure that needs to in place for VIA is highly valuable also for implementation of other screening methods. In contrast, HPV-testing had a high sensitivity, but at the cost of specificity.[37] If HPV-testing becomes cheaper and easier to handle without advanced laboratory facilities, it would be a potential step forward in cervical cancer prevention in Sub-Saharan Africa.

Acknowledgements

  1. Top of page
  2. Abstract
  3. Material and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

The authors would like to thank Ocean Road Cancer Institute screening team for their tireless efforts, and Dr. Sankaranarayanan for his precious help and advices.

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  3. Material and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References
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