Efficiency of the APTIMA HPV Assay for detection of HPV RNA and DNA targets.

BACKGROUND

The APTIMA HPV Assay (AHPV) is designed to detect HPV E6/E7 mRNA from 14 high-risk types in Cytyc PreservCyt liquid-based cytology specimens.

OBJECTIVES

To compare AHPV analytical sensitivity for RNA and DNA; to compare the sensitivity of AHPV and Hybrid Capture 2 (HC2) assays for HPV DNA detection; to compare assay performance with and without sample denaturation; to compare assay results with cytology.

STUDY

DESIGN

Analytical sensitivity of AHPV for detecting E6/E7 RNA was assessed by spiking samples with various quantities of HPV 16 E6/E7 in vitro RNA transcript or HPV 16-positive SiHa cells. AHPV and HC2 analytical sensitivity for HPV 16 DNA was evaluated by spiking samples with various quantities of a plasmid vector containing cloned HPV 16 DNA, or with purified SiHa cell genomic DNA containing integrated HPV 16 genome. Samples were tested using standard AHPV and HC2 protocols. Endocervical samples from 568 women were collected in Digene Specimen Transport Medium. Non-denatured and denatured samples were tested in AHPV and denatured samples with HC2. Assay results were compared to each other, and to cytology.

RESULTS

AHPV had substantially higher (2 4 log(10)) analytical sensitivity for HPV 16 RNA than for HPV 16 DNA. AHPV also had substantially lower (3 log(10)) analytical sensitivity for HPV 16 DNA compared to HC2. The overall agreement between assay results in clinical specimens was 94.2%, but AHPV had fewer positives than HC2 (48.4% positive agreement). In denatured samples, the number of samples testing positive in AHPV increased two-fold, yielding a positive agreement rate of 88.7%. When assay results were compared with cytology, AHPV had fewer positives in samples with normal or ASC-US diagnoses than did HC2.

CONCLUSIONS

AHPV is much more efficient at detecting HPV 16 RNA than DNA. Selective capture, amplification, and detection of HPV RNA by AHPV may improve the specificity of molecular HPV testing.