Brian Lowe

Evaluation of the Hybrid Capture 2 assay for detecting anal high-grade dysplasia

Hybrid Capture 2 (HC2) Human Papillomavirus (HPV) DNA Test® is FDA approved and is a proven aid in detecting HPV infections of the cervix and as an aid in diagnosing, with cytology, cervical disease. A prospective feasibility study was conducted to determine if HC2 testing has utility when screening for high‐grade anal dysplasia (AIN2+). We enrolled 298 patients (45% HIV+) who had AIN2+ screening with cytology, histology and HC2 testing for two specimens: a swab into liquid‐based cytology medium and either a swab or a brush collection in specimen transport medium (STM). High‐resolution anoscopy was performed on all patients with biopsy of AIN2+ suspicious lesions. Cytology was benign (42%), atypical squamous cells of undetermined significance (30%), low‐grade squamous intraepithelial lesion (18%), high‐grade squamous intraepithelial lesion (1%), ASCUS possibly high‐grade dysplasia (1.7%) and nondiagnostic (7%) and 36% had AIN2+ histology. Sensitivity and specificity for predicting AIN2+ histology for any abnormal cytology were 77 and 52%, whereas HC2 sensitivity and specificity were 91 and 40% (p = 0.005 for sensitivity), respectively. There was no significant difference in HC2 sensitivity or specificity between brush and swab or STM and residual cells from cytology. AIN2+ was found in 20% of patients with benign cytology. Only nine AIN2+ specimens were HC2−. This prospective study indicates that HC2 may be useful when screening for anal dysplasia; however, a larger study is recommended.

HPV Genotype Detection Using Hybrid Capture Sample Preparation Combined with Whole Genome Amplification and Multiplex Detection with Luminex XMAP

Infection with a high-risk carcinogenic type of human papillomavirus (HPV) is necessary for the development of cervical cancer. The digene HC2 HPV Test (HC2) is an important screening tool but lacks genotyping capability. To address this issue, we developed an assay for the rapid genotyping of HPV in cervical specimens. The three steps of this assay include Hybrid Capture target enrichment, whole-genome amplification, and Luminex XMAP detection. The assay includes the simultaneous detection of two genomic regions from each of 17 high-risk and two low-risk HPV types most associated with disease. The assay performance was tested on HPV plasmids as well as clinical specimens. An analytical limit of detection of 100 copies or less was demonstrated for linear, circular, and integrated HPV DNA. This finding is at least 1 log lower than the HC2 assay limit of detection. There was no cross-reactivity among the HPV types up to 1,000,000 copies. There was also no substantial assay interference from substances in cervical specimens. Although the clinical performance of the assay was not formally tested, the assay had good agreement (Cohens kappa equal to 0.72) with both a PCR-based HPV genotyping assay (n = 131) and the HC2 assay (n = 502) using representative cervical specimens. This assay may be easy to automate and could be applied for the detection of other targets in future studies.

Detection of human papillomavirus in anal specimens using the hybrid capture 2 assay.

The hc2 human papillomavirus DNA test (HC2) is effective when screening women for cervical dysplasia, and it might be effective in the screening for anal dysplasia. Differences between the anal and the cervical canals could affect the test performance. This prospective study (n=292) measured the HC2 signal and in agreement with a histologic endpoint of high-grade dysplasia for anal specimens collected in various ways. Sensitivities were 91%, 85%, and 62% for specimens collected in a sample transport medium and a liquid-based cytology medium processed by Gyn or Non-Gyn protocol, respectively. HC2 sensitivity and specificity to predict high-grade anal dysplasia were similar for brush or swab specimen collections, but HC2 signal was 6 times higher with the brush. Specificity and sensitivity were similar whether the sample was collected first or after a cytology sample for brush or swab, but swab specimens at the second collection had an HC2 signal (mean) 48% lower than that of the first collection, and the swab cellularity was lower. The presence of maximum stool decreased the HC2 signal in anal swab specimens. Consensus polymerase chain reaction (PCR) confirmed that the 13 human papillomavirus probe types in HC2 were optimal for performance. HC2 could potentially be further investigated for use in screening anal dysplasia. A larger prospective study is indicated.

A hybrid-capture assay to detect HPV mRNA ratios in cervical specimens

Human papillomavirus (HPV) DNA screening benefits cervical cancer diagnosis, but a few HPV infections result in cancer. Assays that predict cancer are desirable. A potential biomarker is the ratio of HPV E6-7 over E2 transcripts, which may increase during early cancer progression. Modified hybrid-capture technology detected, in separate wells, HPV E6-7 or E2 mRNA of HPV 16 or HPV 18 in samples. The limit of detection was approximately 1000 copies of in vitro transcribed RNA with linear dynamic range approximately four logs. No cross-reactivity between HPV 16 and HPV 18 mRNAs was detected. RNA of SiHa cells was stable in clinical specimen pools for 67 days, as determined by RT-PCR. The ratio of HPV E6-7:E2 mRNAs was relatively high for cancer cells lines, SiHa, Caski and HeLa cells preserved in clinical specimen pools. A broad distribution of HPV 16 E6-7:E2 mRNA ratio was detected in a small set of clinical specimens with various histological diagnoses. Some specimen ratios were so high for cancer cell lines, but the significance of the results needs to be determined. This method may help determine the pattern of gene expression in HPV-related disease or in other systems.

Distribution of Human papillomavirus load in clinical specimens

The information about the range and distribution of Human papillomavirus load in clinical specimens is important for the design of accurate clinical tests. The amount of Human papillomavirus in cervical specimens was estimated using the digene HC2 HPV DNA Test(®) (QIAGEN). This semi-quantitative assay is based on linear signal amplification with an analytical limit-of-detection of approximately 2500 virus copies per assay and 3-4 log dynamic range. The dynamic range of the assay was extended by a serial dilution strategy. Two large sets of positive specimens (n=501 and 569) were analyzed and 9-11% of specimens was estimated to contain more than 7 × 10(7) copies of virus. The viral load was also assessed for an assortment of specimens with known cytology diagnoses (n=9435) and histological diagnoses (n=2056). The percentage of specimens with more than 7 × 10(7) copies of virus was estimated to be 0.89 for normal cells, 4.2 for atypical cells (unknown significance), 14.31 for cells of low-grade lesions and 22.24 for cells of high-grade lesions. The viral load increased with disease severity, but its broad distribution may not support its use as a disease biomarker. This information is important for assay design and automation, where cross-reactivity and sample-to-sample contamination must be addressed rigorously.