Current triage strategies for primary HPV screening include cytology and HPV genotyping. Other biomarkers, such as p16/Ki-67 dual stain cytology, have shown promise for triage of HPV-positive women. However, increasing prophylactic HPV vaccination alters HPV type distribution and reduces incidence of cervical cancer precursors in the population, which affects performance of cervical cancer screening and triage tests. Therefore, it is important to evaluate triage markers in vaccinated women. The performance of dual stain cytology was evaluated in 1,500 women ages 18-29 from the Costa Rica Vaccine Trial vaccinated against HPV-16/18 or Hepatitis A (HAV). Cytology slides were stained with the CINtec plus dual stain assay. Assay performance for detection of cervical precancer was evaluated stratified by study arm in women who were negative for vaccine types at baseline and who received all doses of the vaccine (according to protocol, ATP). Dual stain positivity was 11.8% among women who received the HPV 16/18 vaccine and 22.9% among those who received the HAV vaccine. Similar sensitivity of the dual stain was observed between the two arms, but specificity was higher in women who received HPV-16/18 compared to women who received the HAV vaccine. Dual stain positivity was 52% among HPV16-positive controls compared with 23% for controls positive for other carcinogenic types (p<0.0001), accounting for the higher specificity in the HPV vaccinated arm, which included few HPV16-positive controls. In this first evaluation of p16/Ki-67 staining in young vaccinated women, we observed good risk stratification of the dual stain assay for cervical precancer. The performance improved in HPV-vaccinated women, supporting further evaluation of the assay for age-appropriate screening of vaccinated populations.
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