Intra- and interlaboratory reproducibility evaluation toward international validation status of the AmpFire assay.

To meet the screening goal of WHO's 90-70-90 strategy aimed at eliminating cervical cancer (CC) by 2030, clinical validation of human papillomavirus (HPV) assays is essential to provide accurate and valid results through fulfilling three criteria of the international validation guidelines (IVGs). Previously, the clinical accuracy of the AmpFire® HPV Screening 16/18/HR assay (AmpFire assay) was reported but reproducibility data are lacking. Here, we aim to evaluate the intra- and inter-laboratory reproducibility of the AmpFire assay. The reproducibility of the isothermal AmpFire assay was assessed using 556 cervical cell samples collected from women attending CC screening and biobanked in a Belgian HPV national reference center. This assay detects HPV16, HPV18, and 12 other high-risk HPV (hrHPV) types (31/33/35/39/45/51/52/56/58/59/66/68) in aggregate. Lower 95% confidence interval bound around the assay's reproducibility should exceed 87%, with κ ≥ 0.50. Additionally, a literature review of the assay's clinical performance was performed. The AmpFire assay showed an excellent intralaboratory (96.4%, 95% CI:94.5-97.8%, κ = 0.920) and interlaboratory (95.3%, 95% CI:93.2-96.9%, κ = 0.897) reproducibility. One study demonstrated noninferior sensitivity of a prototype AmpFire assay targeting 15 hrHPV types (including HPV53) to detect CIN2+. However, clinical specificity became similar to the comparator after removing HPV53 from analyses. The low-cost and easy-to-use AmpFire assay presents excellent reproducibility and-after removing HPV53 from the targeted types-fulfills also clinical accuracy requirements. Inclusion of HPV53, which is not recognized as carcinogenic, comprises clinical specificity of screening assays.

AmpFire HPV and ScreenFire RS HPV validation trial.

OBJECTIVES: The human papillomavirus (HPV) screening assays from Atila Biosystems, including the new AmpFire (14 type) and ScreenFire RS (13 type), were subjected to a series of validation tests. METHODS: We used a set of samples from the Chinese Multi-Site Screening Trial (previously tested with cobas 4800 and the next-generation SeqHPV) to satisfy Meijer's criteria for clinical end-point validation. We selected 556 self-collected specimens composed of 273 high-risk HPV (hrHPV) positives and 283 hrHPV negatives on the cobas 4800 and SeqHPV. Of the 273 hrHPV-positive cases, 108 had a disease end point of cervical intraepithelial neoplasia grade 2 (CIN2) or higher, including 47 with cervical intraepithelial neoplasia grade 3 (CIN3+) or higher. We simulated the VALGENT framework for inter- and intralaboratory validation and evaluated the new 4-channel risk-stratified ScreenFire assay in a hierarchal fashion. RESULTS: Both AmpFire and ScreenFire detected 106 (98.1%) of 108 cases with CIN2 or higher, with specificities of 56.7% and 58.1%, respectively. Intralaboratory concordance for 2 runs of AmpFire and ScreenFire was 95.13% and 96.03%, respectively, for overall hrHPV types and 99.10% and 99.46%, respectively, for HPV 16. The interlaboratory concordance of AmpFire and ScreenFire was 93.68% and 94.04% for overall hrHPV and 98.92% and 99.28%, respectively, for HPV 16. Other genotype correlation percentages were similarly high, with κs ranging from 0.86 to 0.94. The ScreenFire RS assay demonstrated excellent "genotype-specific concordance" when evaluated for "clinical guidance" in a hierarchal fashion (noting only the highest risk channel) with both the cobas 4800 and SeqHPV for less than CIN2, CIN2, and CIN3 or higher. CONCLUSIONS: The excellent intra- and interlaboratory reproducibility and the established clinical performance, together with the platforms' simplicity, make these assays particularly applicable to low-resource settings.

Comparison of high-risk HPV detection by the AmpFire® HPV Screening 16/18/HR technique (Atila Biosystems) and the hybrid capture 2 test (Qiagen).

BACKGROUND: Detection of high-risk human papillomaviruses (hrHPV) is widely used at the first line of cervical cancer screening, requiring rigorous validation of the clinical performance of commercial kits designed for this indication. METHODS: Performance of the AmpFire HPV Screening 16/18/HR test (AF, Atila Biosystems) and the Hybrid Capture 2 test (HC2, Qiagen) for detecting hrHPV was cross-compared in 200 cervical samples in our institution. RESULTS: The global percentage of agreement between the 2 techniques was 95.0% (95%CI 92-98%) with a Cohen's kappa coefficient of 0.85 (95%CI 0.75-0.94). Ten samples showed discordant results between the 2 techniques in both directions (5 HC2+/AF- and 5 HC2-/AF+). Among possible explanations for these discrepancies was the detection of HPV66 and HPV53 genotypes in two samples, since these genotypes are targeted by the Ampfire test but not by the HC2 test, as well as intrinsic differences in analytical performance to target specific genotypes. CONCLUSIONS: A high level of agreement was observed between the two techniques, which encourages further testing in order to definitively validate the use of the Ampfire kit for primary cervical cancer screening.

A comparative analysis of cycle threshold (Ct) values from Cobas4800 and AmpFire HPV assay for triage of women with positive hrHPV results.

BACKGROUND: To compare the triage performance of HPV viral loads reflected by cycle threshold values (CtV) from two different HPV testing assays: the PCR based Cobas4800 and the isothermal amplification based AmpFire assay. METHODS: We used the data from a sub-study of The Chinese Multi-Center Screening Trial and analyzed the data of the cases positive in both Cobas4800 and AmpFire assays with recorded CtV. Spearman's correlation was applied to analyze the association between CtV from AmpFire and Cobas4800 assays, as well as the correlation between CtV and the histological lesion grades. The 50th percentile of CtV was used as the cutoff to construct triage algorithms for HPV-positive cases. McNemar's test was used to analyze the differences in sensitivity and specificity for detecting CIN2 + and CIN3 + in different triage algorithms. RESULTS: Four hundred forty-six HPV positive women who had consistent HPV results from Cobas4800 and AmpFire in terms of the HPV genotype and reported Ct values were included in the analysis. The mean CtV of hrHPV tested by Cobas4800 and AmpFire were linear correlated. Direct association were showed between the severity of cervical lesions and the HPV viral loads reflected by CtV of hrHPV, HPV16, non-16/18 hrHPV and A9 group from both assays. HPV16/18 genotyping combined with low-CtV for non-16/18 hrHPV, especially A9 group, were demonstrated to be satisfactory in the sensitivity and specificity for detecting CIN2 + or CIN3 + . CONCLUSION: Ct value represented a good triage marker in both PCR-based and isothermal amplification HPV detection.

Comparison of AmpFire and MY09/11 assays for HPV genotyping in anogenital specimen of Rwandan men who have sex with men.

Introduction: The AmpFire HPV genotyping Assay (Atila Biosystems, Mountain View, CA, USA) is a new test for which there are few data regarding its analytic performance and reliability. Using anal and penile swab specimens from a cohort study of men who have sex with men (MSM) in Rwanda, we compared high-risk HPV (hrHPV) detection by AmpFire done at two laboratories, one at University of California San Francisco (UCSF) and the other Rwanda Military Hospital, and well-validated MY09/11-based assay done at UCSF. Methods: Anal and penile specimens collected from 338 MSM from March 2016 to September 2016 were tested for high-risk HPV genotypes (hrHPV) by MY09/11, AmpFire UCSF and AmpFire RMH. Cohen's kappa coefficient was used to test for reproducibility. Results: The hrHPV positivity by MY09/11 and AmpFire UCSF was 13% and 20.7% (k = 0.73) for anal specimens and was 26.3% and 32.6% (k = 0.67) for penile specimens. Specifically, good reproducibility was for types 16 and 18 (k = 0.69 and k = 0.71) for anal specimens and (k = 0.50 and k = 0.72) for penile specimens. The hrHPV positivity by AmpFire at UCSF and RMH was 20.7% for both laboratories (k = 0.87) for anal specimens and was 34.9% and 31.9% (k = 0.89) for penile specimens. Specifically, excellent reproducibility was for types 16 and 18 for anal specimens (k = 0.80 and k = 1.00) and penile specimens (k = 0.85 and k = 0.91). Conclusion: Results show that MY09/11 and AmpFire assays have good reproducibility while the AmpFire UCSF and RMH assays have excellent reproducibility. These results show that AmpFire is a promising HPV genotyping test.

Comparison of the AmpFire® Multiplex HPV Assay to the Xpert® HPV Assay for detection of human papillomavirus and cervical disease in women with human immunodeficiency virus: a pragmatic performance evaluation.

BACKGROUND: Low- and middle-income countries (LMICs) account for nearly 85% of the global cervical cancer burden, yet have the least access to high-performance screening. International guidelines recommend human papillomavirus testing (HPV) as primary screening, yet implementation is inhibited by the cost of HPV testing. Atila AmpFire® HPV Assay (AmpFire) is both affordable and easy to use, and offers individual genotyping. The objective of this study was to compare the performance of the AmpFire HPV assay to the Xpert® HPV assay in detection of both HPV and clinically significant cervical disease. METHODS: We utilized stored cervical specimens from a prospective cohort study of women living with human immunodeficiency virus (HIV) in Botswana conducted from May to July 2018. Positive and negative percent agreement was calculated for the AmpFire and Xpert assays, as was detection of high-grade cervical dysplasia. RESULTS: 63 stored cervical specimens had detectable DNA after thawing and were included in the analysis. The positive percent agreement was 91.2% (95%CI 76.3-98.1) and negative percent agreement was 79.3% (95% CI 60.3-92.0). Six cases positive by AmpFire but negative by Xpert were HPV genotypes 35, 52 (n = 2), 58, 68, and co-infection with HPV 45 and 68. Both Xpert and AmpFire assays detected HPV in all 10 samples of women who had high-grade cervical dysplasia. CONCLUSIONS: The AmpFire HPV assay demonstrated excellent analytic performance in both detection of HPV and clinically significant cervical disease. AmpFire HPV is a promising option to increase access to affordable, type-specific HPV screening for cervical cancer in LMICs.

Comparison of the AmpFire and MA-6000 polymerase chain reaction platforms for high-risk human papillomavirus testing in cervical precancer screening.

High-risk human papillomavirus (hr-HPV) testing for primary cervical precancer screening offers an opportunity to improve screening in low-middle income countries (LMICs). This study aimed to compare the analytic performances of the AmpFire and MA-6000 platforms for hr-HPV DNA testing in three groups of women screened for hr-HPV types in Ghana: group 1 with 33 GeneXpert-archived ThinPrep/liquid-based samples subjected to both tests, group 2 with 50 AmpFire-archived dry brush samples subjected to MA-6000 testing, and group 3 involving 143 cotton swab samples simultaneously subjected to both tests without archiving. The overall agreement rates were 73 %, 92 %, and 84 %, for groups 1-3, respectively, and 84 % (95 % CI, 78.6-88.6) for the entire group. Neither AmpFire nor MA-6000 was more likely to test hr-HPV positive in all three groups and the combined group. Group 1 showed fair agreement without statistical significance (κ = 0.224, 95 % CI, -0.118 to 0.565), while group 3 showed significant moderate agreement (κ = 0.591, 95% CI, 0.442-0.741). Group 2 showed an almost perfect significant level of agreement (κ = 0.802; 95 % CI, 0.616-0.987). Thus, both platforms showed statistically significant moderate to near-perfect agreement for detecting hr-HPV in cervicovaginal samples, with variation according to archiving conditions and duration between sample collection and retesting. For LMICs using these platforms for COVID-19 testing, as the COVID-19 pandemic subsides, the platforms can become available for running other tests such as hr-HPV DNA testing for cervical precancer screening.

Agreement between Xpert and AmpFire tests for high-risk human papillomavirus among HIV-positive women in Rwanda.

Background: High-risk human papillomavirus (hrHPV) may cause more than 99% of cervical cancers worldwide. Little is known about performance differences in tests for hrHPV. Objective: This study analysed agreement for detection of hrHPV between the established, clinically validated Xpert HPV assay and the novel isothermal amplification-based AmpFire HPV genotyping assay. Methods: This study was nested in a larger project on cervical cancer screening among approximately 5000 women living with HIV in Kigali, Rwanda. This sub-study included 298 participants who underwent initial screening for cervical cancer using the Xpert HPV assay and visual inspection with acetic acid in 2017 and tested positive by either or both. Participants were rescreened using colposcopy, and cervical samples were collected between June 2018 and June 2019. Samples were then tested for HPV using the Xpert HPV assay and AmpFire HPV genotyping assay. Agreement between results from both tests was analysed using an exact version of McNemar test and chi-square test. Results: Overall agreement and kappa value for detection of hrHPV by Xpert and AmpFire were 89% and 0.77 (95% confidence interval: 0.70-0.85). AmpFire was marginally more likely to diagnose hrHPV-positive than Xpert (p = 0.05), due primarily to the extra positivity for HPV16 (p < 0.001). Conclusion: Overall, there was good to excellent agreement between the Xpert and AmpFire when testing hrHPV types among women living with HIV. AmpFire was more likely to test extra cases of HPV16, the most carcinogenic HPV type, but the clinical meaning of detecting additional HPV16 infections remains unknown.

Evaluation of an isothermal amplification HPV detection assay for primary cervical cancer screening.

OBJECTIVE: The aim of this research was to evaluate independently the performance of a new isothermal amplification assay for cervical cancer screening compared to two previously validated PCR-based assays and histologic endpoints. METHODS: This is a sub-study from the Chinese multi-center screening trial (CHIMUST). The self-collected and clinician-collected specimens stored in PreservCyt at - 4 °C from 6042 women with complete data were tested with the AmpFire assay. These specimens had been previously tested with Cobas and SeqHPV assays. In the primary study all patients with an abnormal test were referred to colposcopy where all had directed and/or random biopsies plus ECC. No additional patients were called back based on the AmpFire results. RESULTS: 6042/6619 women had complete data (mean age 44.1). There were 57 cases of CIN 2, 35 cases of CIN 3 and 2 cancers. The sensitivity for CIN2+ and CIN3+ were similar among the three assays (both direct and self-collected). For the specificities in all categories (CIN2+/CIN3+ and self and direct collection), isothermal amplification assay was either equal to or more specific than Cobas but consistently less specific than SeqHPV. CONCLUSION: The AmpFire HPV assay showed similar sensitivity to Cobas and SeqHPV for CIN2+ and CIN3+ on both self and clinician-collections (P>0.05), with good specificity. The speed, low cost, and simplicity of this assay will make it particularly suited for low and middle resource settings. Its accuracy with self-collection makes it applicable for mass screening programs.

Detection of high-risk human papillomavirus (HPV) by the novel AmpFire isothermal HPV assay among pregnant women in Pemba Island, Tanzania.

INTRODUCTION: human papillomavirus (HPV) is the most common sexually transmitted virus in the world. Prevalence of infection differs, with highest rates reported in sub-Saharan African, including the country of Tanzania. In pregnancy, the hormonal changes and immune changes seem to facilitate HPV persistence, increasing the cancer risk and the risk of vertical transmission towards the placenta and the fetus. The burden of HPV infection is still high despite multiple screening and detection test available. The AmpFire® HPV assay is a novel nucleic acid isothermal amplification with real-time fluorescence detection assay that can test simultaneously 15 high-risk HPV. This nested cohort study aims to contribute evidence on the prevalence of HPV infection and persistence across two time points among pregnant women in Pemba island, Tanzania. METHODS: vaginal swabs that were previously collected during pregnancy were stored in eNAT buffer (n1=385 and n2=187) and were tested with AmpFire® screening assay, for simultaneous detection of the HPV 16, 18 and other high-risk HPV genotypes 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66 and 68. RESULTS: the AmpFire® HPV assay detected an 11% and 6% high-risk HPV prevalence at the two time points among pregnant women in Pemba island, consecutively. For the 133 women whose samples were tested at both time points, the persistence rate of high-risk HPV was 64%. CONCLUSION: novel isothermal HPV assay, such as the AmpFire®, might be feasible to use in low-income regions.