Population specific HPV prevalence studies are useful for planning vaccine and screening strategies. Our objective was to assess the prevalence of high-risk (HR) and low-risk (LR) HPV in women attending routine cervical screening in rural Malawi using a new, analytically sensitive genotyping assay.
Provider-taken and self-taken specimens were obtained between January 2016 and March 2017 from women attending routine VIA (Visual Inspection with Acetic acid) clinics in Nkhoma Hospital and associated Health Centres. All samples had previously been tested using the Xpert® HPV assay. Samples were classified based on VIA and Xpert results into four categories: VIA+/Xpert+; VIA+/ Xpert -; VIA-/ Xpert +; VIA-/ Xpert -.
A multiplex real-time PCR based assay (Papilloplex Any HPV; GeneFirst, UK) was performed which provides individual genotyping in two tubes (14 HR-HPV:16, 18, 31, 33, 35, 39, 45, 51, 52, 58, 59, 56, 66, 68(a&b) and 16 LR-HPV: 6, 11, 26, 40, 42, 43, 44, 53, 54, 61, 67, 69, 70, 72, 81, 82). HPV type specific prevalence of HPV in all four categories and concordance with Xpert were assessed.
High concordance was seen in HR-HPV positivity between Xpert and Papilloplex HPV in provider-taken {proportional agreement=0.98 (95% CI- 0.79-0.90), k=0.68 (95% CI- 0.58-0.79)} and in self-taken samples {proportional agreement=0.97 (95% CI- 0.77-0.92), kappa=0.72 (95% CI- 0.57-0.80)}.
HR- and LR-HPV prevalence is summarised in Table 1. HPV 16 was most common in VIA+ women (N=156) followed by 52, 18, 51, 35, 31/33/45. HPV 6/44 then 67/72 were the most common LR-HPV. HPV 16 was also most common in VIA- women (N=139) followed by 52, 51, 35, 58 and 31/33 with the most frequent LR-HPV being 6 then 44/67/72/54/61. In women with a VIA assessment of ‘suspicious/frank cancer’ (N=42), HPV 16 was most frequent followed by 18, 45, 52, 31 and 51.
| Sample sets (VIA and Xpert HPV results) | HR-HPV prevalence | HR-HPV prevalence | LR-HPV prevalence | LR-HPV prevalence |
|---|---|---|---|---|
|
Provider-taken |
Self-taken | Provider-taken |
Self-taken |
|
| VIA+/Xpert+ |
85.18% |
82.61% |
20.97% |
21.74% |
| VIA+/Xpert- | 13.79% | 4.17% | 15.69% | 4.17% |
| VIA-/Xpert+ | 87.10% | 80% | 25.0% |
13.3% |
| VIA-/Xpert- | 19.04% | 15.38% | 11.1% | 3.84% |
In both VIA+ and VIA- groups, HPV 16 is the most common HPV type in women attending screening clinics in rural Malawi followed by types 52, 51, 35, 18 and 31. However, HPV 16, 18, 45 are the three most common types found in visually assessed suspicious cancers. High concordance was seen between the two tests but analytically sensitive Papilloplex assay detects higher prevalence of HR HPV prevalence. Further studies on type specific prevalence using analytically sensitive assays are warranted in clinical settings in low income countries.