False-positive Human Papillomavirus DNA tests in cervical screening: it is all in a definition

A fully integrated paperfluidic molecular diagnostic chip for the extraction, amplification, and detection of nucleic acids from clinical samples

Paper diagnostics have successfully been employed to detect the presence of antigens or small molecules in clinical samples through immunoassays; however, the detection of many disease targets relies on the much higher sensitivity and specificity achieved via nucleic acid amplification tests (NAAT). The steps involved in NAAT have recently begun to be explored in paper matrices, and our group, among others, has reported on paper-based extraction, amplification, and detection of DNA and RNA targets. Here, we integrate these paper-based NAAT steps into a single paperfluidic chip in a modular, foldable system that allows for fully integrated fluidic handling from sample to result. We showcase the functionality of the chip by combining nucleic acid isolation, isothermal amplification, and lateral flow detection of human papillomavirus (HPV) 16 DNA directly from crude cervical specimens in less than 1 hour for rapid, early detection of cervical cancer. The chip is made entirely of paper and adhesive sheets, making it low-cost, portable, and disposable, and offering the potential for a point-of-care molecular diagnostic platform even in remote and resource-limited settings.

Prevalence of Human Papillomavirus infection in unselected SurePath samples using the APTIMA HPV mRNA assay

The APTIMA Human Papillomavirus (HPV) Assay detects E6/E7 mRNA from 14 human papillomavirus genotypes. Horizon was a population-based split-sample study among well-screened women, with an aim to compare APTIMA, Hybrid Capture 2 (HC2), and liquid-based cytology (LBC) using SurePath samples. APTIMA testing on the PANTHER platform, and HC2 testing on the Rapid Capture System were performed in accordance with protocols agreed on with the manufacturers before the study, on 5070 consecutive, routine, cervical cytology samples from Copenhagen, Denmark. In this high-risk population, 17% of all samples tested positive on APTIMA, 20% of samples tested positive on HC2, and 7% of samples had abnormal cytology. Among the 4411 samples without recent abnormalities, 15% tested positive on APTIMA, 19% tested positive on HC2, and 5% had abnormal cytology. The κ coefficient of 0.75 suggested substantial agreement between APTIMA and HC2. This is the first APTIMA study using SurePath samples on the PANTHER platform. The trends in positivity rates on SurePath samples for APTIMA, HC2, and LBC were consistent with studies based on PreservCyt samples, and the agreement between the two HPV assays was substantial. The high proportions of women testing positive suggest that in countries with a high HPV prevalence, caution will be needed if HPV tests, including mRNA-based tests, are to replace LBC.

Human papillomavirus testing in primary cervical screening and the cut-off level for hybrid capture 2 tests: systematic review

OBJECTIVE

To determine the trade-off between the sensitivity and the specificity for high grade cervical intraepithelial neoplasia at hybrid capture 2 cut-off values above the standard ≥ 1 relative light units/cut-off level (rlu/co).

DESIGN

Systematic review.

DATA SOURCES

PubMed.

STUDY SELECTION

Randomised controlled trials in primary cervical screening using hybrid capture 2 testing in the intervention arms. Articles published until August 2010 were included if the numbers of women with positive test results and with cervical intraepithelial neoplasia were stratified by hybrid capture 2 cut-off levels.

PARTICIPANTS

Women in the baseline screening rounds of the trials.

INTERVENTIONS

Hybrid capture 2 screening in the baseline round including the diagnostic follow-up as practised in the randomised controlled trials and as reported by hybrid capture 2 cut-off values.

RESULTS

Owing to heterogeneity in the trials, meta-analysis was not possible. Including cut-off values up to ≥ 10 rlu/co, 25 observation points were available for analysis. The relative sensitivity for cervical intraepithelial neoplasia grade III or higher at cut-off levels of ≥ 2, ≥ 4 or ≥ 5, and ≥ 10 rlu/co compared with a cut-off level of ≥ 1 rlu/co varied by trial, but at their lowest they were 0.97, 0.92, and 0.91, respectively. A similar pattern was observed for cervical intraepithelial neoplasia grade II or higher. The specificity would increase by at least 1%, 2%, and 3%, respectively, so that up to 24%, 39%, and 53%, of positive hybrid capture 2 test results not associated with high grade neoplasia could be avoided. Only two outliers existed to this general pattern.

CONCLUSIONS

Although the data were derived from the baseline screening rounds only, the decrease in the sensitivity for high grade cervical intraepithelial neoplasia using a hybrid capture 2 cut-off level between ≥ 2 rlu/co and ≥ 10 rlu/co seemed acceptable given the international recommendations for testing for human papillomavirus DNA in cervical screening, which require 90% or more sensitivity for cervical intraepithelial neoplasia grade II or higher compared with hybrid capture 2 at ≥ 1 rlu/co. The data suggest that the hybrid capture 2 cut-off level could be increased in primary screening; this seems reasonably safe and is significantly less burdensome for women.