The challenges of defining sample adequacy in an era of HPV based cervical screening

Human papillomavirus testing using HPV APTIMA® assay and an external cellularity control in self-collected samples

In cervical cancer screening programs, the detection of high-risk human papillomavirus (HR-HPV) is now widely implemented on physician-collected samples and has expanded to include self-collected samples. The use of a cellularity control (CC) is needed to reduce false-negative HPV results. An external mRNA CC for the HPV APTIMA® assay was assessed for its analytical performance and the results were compared with both cervix cytobrush samples taken by physicians and self-collected vaginal samples from 148 women. The performance of the CC was adjusted to control for the presence of cellular mRNA in the ThinPrep® and Multitest® transport media. This CC is user-friendly but implies to perform two independent assays on PANTHER® automate. Self-collected vaginal sampling gives a lower median CC results (13.2 vs. 16.9 min) but a higher risk of negative CC results (3.3 vs. 0%). The usefulness of the CC for the HR-HPV assay may be optimized by the definition of a threshold for a minimum cell number to be tested to increase confidence in HPV-negative results. The systematic use of an RNA CC increases confidence for HPV RNA assays on self-collected vaginal samples.

Intra- and interlaboratory reproducibility of the RIATOL qPCR HPV genotyping assay

The implementation of cervical screening based on human papillomavirus (HPV) continues to progress rapidly across countries. Evidence has shown that assays detecting high-risk human papillomavirus (hrHPV) deoxyribonucleic acid (DNA) are more effective than cytology-based screening. Validation of new hrHPV DNA assays requires both noninferior clinical accuracy compared to a standard comparator for cervical precancer and good reproducibility. This study builds upon previous diagnostic accuracy assessments of the RIATOL HPV genotyping qPCR assay and aims to evaluate the international validation criteria for reproducibility. The intra- and interreproducibility of the RIATOL-qPCR assay were assessed using 550 remnant cervical cell material from the cytology archive of the National Reference Center for HPV in Belgium. Specimens were collected in the context of cervical cancer screening and tested in two different laboratories. The international reproducibility criteria include the lower bound of 95% confidence interval of the intra- and interlaboratory agreement regarding the detection of hrHPV DNA exceeding 87% with kappa ≥0.50. The RIATOL-qPCR assay demonstrated excellent intralaboratory reproducibility, achieving an overall agreement of 98.2 (95% CI 96.6-99.1%) and a kappa of 0.96. Interlaboratory testing showed an overall agreement of 98.5 (95% CI 97.1-99.4%) with a kappa of 0.97. The RIATOL-qPCR assay fulfills the third criterion for HPV test reproducibility requirement for use in cervical cancer screening.

Quality assurance in human papillomavirus testing for primary cervical screening

The recommendation for cervical screening is that it should be based on human papillomavirus (HPV) molecular testing. For all screening programs, attention to quality assurance is required to fully realize the benefits. Internationally recognized quality assurance recommendations for HPV-based screening are needed that are ideally applicable for a variety of settings, including in low- and middle-income countries. We summarize the main points of quality assurance for HPV screening, with a focus on the selection, implementation, and use of an HPV screening test, quality assurance systems (including internal quality control and external quality assessment), and staff competence. While we recognize that it might not be possible to fulfill all points in all settings, an awareness of the issues is essential.

Papilloplex HR-HPV test has non-inferior clinical performance for detection of human papillomavirus infection: assessment using the VALGENT framework

AIM

The Papilloplex high-risk human papillomavirus (hrHPV) test (Genefirst, Oxford, UK) is a single tube real-time HPV test which provides multiplex detection and separate identification of 14 hrHPV types. Here, we present the clinical validation of the test in SurePath samples in comparison to a clinically validated reference test, the GP5+/6+Enzyme ImmunoAssay (GP5+/6+EIA) using the VALGENT (VALidation of HPV GENotyping Tests) framework.

METHODS

Clinical performance was assessed using 998 unselected, cervical screening samples enriched with 297 cytologically abnormal specimens (100 atypical squamous cells of unspecified significance, 100 low-grade squamous intraepithelial lesions, 97 high-grade squamous intraepithelial lesions). Cases were defined as women diagnosed with histologically confirmed cervical intraepithelial neoplasia two or more (≥CIN2, N=119) and controls defined as women with two subsequent negative cytology results (N=834).

RESULTS

The Papilloplex HR-HPV test has non-inferior sensitivity for detection of cervical precancer (p=0.0001 for ≥CIN2 and p=0.0005 for ≥CIN3) and non-inferior specificity, compared with GP5+/6+EIA (pni=0.0167)). The assay also showed excellent or good agreement for overall hrHPV and nearly all individual HPV types as compared with GP5+/6+EIA/Luminex.

CONCLUSION

The Papilloplex HR-HPV applied on cervical specimens stored in SurePath medium fulfils the international clinical accuracy criteria for use in cervical cancer screening.

Clinical performance of primary HPV screening cut‐off for colposcopy referrals in HPV vaccinated cohort: observational study

OBJECTIVE

To understand the effect of changing from cytology-based to primary HPV screening on the positive predictive value (PPV) of colposcopy referrals for cervical intraepithelial neoplasia (CIN) in a cohort offered HPV vaccination.

DESIGN

Retrospective pre/post observational cohort study.

SETTING

Scotland.

POPULATION OR SAMPLE

2193 women referred to colposcopy between September 2019 and February 2020 from cytology-based screening and between September 2020 and February 2021 from primary high-risk HPV (hrHPV) screening.

METHODS

Calculating positive predictive values (PPVs) for two cohorts of women; one having liquid-based cytology screening and the other, the subsequent hrHPV cervical screening as a pre/post observational study.

MAIN OUTCOME MEASURES

Positive predictive values of LBC and hrHPV cut-offs for colposcopy referral for CIN at colposcopy.

RESULTS

Three papers fitted our criteria; these reported results only for cytology-based screening. The PPV was lower for women in HPV-vaccinated cohorts indicating a lower prevalence of disease. Vaccination under the age of 17 had the lowest PPV reported. Scottish colposcopy data concerning hrHPV and cytology showed a non-significant difference between PPV (17.5%, 95% CI 14.3-20.7, and 20.6, 95% CI 16.7-24.5, respectively) for referrals with a cut-off of low grade dyskaryosis (LGD); both met the standard set of 8-25%. The hrHPV PPV (66.7, 95% CI 56.8-76.6) was comparable to cytology (64.1, 95% CI 55.8-72.4) for referrals with a cut-off of high grade dyskaryosis (HGD) but neither met the standard set of 77-92%.

CONCLUSIONS

Current literature only provides PPVs for LBC and, overall, the vaccinated cohort had lower PPVs. Only LG dyskaryosis met PHE criteria. The PPV for HPV-vaccinated women undergoing either LBC or HR-HPV screening were not statistically different. However, similar to papers in the current literature, HG dyskaryosis (HGD) PPVs of both techniques did not meet the PHE threshold of 76.6-91.6% outlined in the cervical standards data report.

Importance of Adequate qPCR Controls in Infection Control

Respiratory screening assays lacking Sample Adequacy Controls (SAC) may result in inadequate sample quality and thus false negative results. The non-adequate samples might represent a significant proportion of the total performed tests, thus resulting in sub-optimal infection control measures with implications that may be critical during pandemic times. The quantitative sample adequacy threshold can be established empirically, measuring the change in the frequency of positive results, as a function of the numerical value of “sample adequacy”. Establishing a quantitative threshold for SAC requires a big number/volume of tests to be analyzed in order to have a statistically valid result. Herein, we are offering for the first time clear clinical evidence that a subset of results, which did not pass minimal sample adequacy criteria, have a significantly lower frequency of positivity compared with the “adequate” samples. Flagging these results and/or re-sampling them is a mitigation strategy, which can dramatically improve infection control measures.

Self-sampling as the principal modality for population based cervical screening: Five-year follow-up of the PaVDaG study

Self-sampling provides a powerful means to engage women in cervical screening. In the original Papillomavirus Dumfries and Galloway study (PaVDaG), we demonstrated cross-sectional similarity of high-risk human papillomavirus (Hr-HPV) testing on self-taken vaginal vs clinician-taken samples for the detection of cervical intraepithelial neoplasia 2 or worse (CIN2+). Few data exist on the longitudinal performance of self-sampling; we present longitudinal outcomes of PaVDaG. Routinely screened women provided a self-taken and a clinician-collected sample. Ninety-one percent of 5136 women from the original cohort completed a further screening round. Sensitivity, specificity, positive predictive value and complement of the negative predictive value of the Hr-HPV test on self-samples for detection of CIN2+ and CIN3+ up-to 5 years after testing were determined. Additionally, clinical accuracy of Hr-HPV testing on vaginal and clinician-collected samples was assessed. A total of 183 CIN2+ and 102 CIN3+ lesions were diagnosed during follow-up. Risk of CIN2+ and CIN3+ following an Hr-HPV negative self-sample was 0.6% and 0.2%, respectively, for up to 5 years after testing. The relative sensitivity for CIN3+ and specificity for ≤CIN1 of Hr-HPV testing on self-taken specimens was slightly lower vs clinician-collected samples: 0.95 (95% CI: 0.90-0.99; P^McN = .0625) and 0.98 (95% CI: 0.95-1.00; P^McN  = <.0000), respectively. The low risk of CIN2+ in women with Hr-HPV-self-sample(s) suggests, that the 3 to 5-year recall interval implemented in several cervical screening settings, based on clinician-taken samples, may be safe for self-samples. Future assessment will show if "universal" 5-year screening is appropriate for programs based on self-sampling.

Sample Adequacy Control (SAC) Lowers False Negatives and Increases the Quality of Screening: Introduction of "Non-Competitive" SAC for qPCR Assays

Sample Adequacy Control (SAC) has critical analytical, clinical and epidemiological value that increases confidence in a negative test result. The SAC is an integral qPCR assay control, which ensures that all pre-analytical and analytical steps are adequate for accurate testing and reporting. As such, a negative SAC with a negative result on pathogen screen specifies that the result should be reported as inconclusive instead of negative. Despite this, many regulatory approved tests do not incorporate SAC into their assay design. Herein, we emphasize the universal value of SAC and offer for the first time, a simple technical strategy to introduce non-competitive SAC which does not interfere with the limit of detection for the screened pathogen. Integration of SAC can provide key benefits towards identifying, isolating, quarantining and contact tracing infected individuals and in turn can improve worldwide efforts in infection control.