A pilot study to compare dry cervical sample collection with standard practice of wet cervical samples for human papillomavirus testing

Background: For human papillomavirus (HPV) DNA detection, specimen collection and transportation using a dry swab without transport medium has advantages, in various situations, over liquid media.

Objective: In this pilot study we evaluated whether a dry cervical sample taken with a flocked swab (dry sample) is a valid alternative for HPV DNA testing compared with the standard practice of a wet sample taken with a cyto-broom placed directly into liquid media (wet sample).

Study design: Women attending the dysplasia clinic at the Royal Women's Hospital, Melbourne Australia between November 2013 and February 2014 were enrolled. During colposcopic examination, a practitioner collected wet and dry cervical samples, with the order of collection randomised. In the laboratory both samples were left for a week before being tested for 14 high-risk HPV types using the Roche Cobas 4800 test.

Results: Overall, 209 had valid HPV results from both samples. The observed agreement for HPV detection between wet and dry samples was 92.8% and kappa was 0.85 (95% confidence interval (95% CI): 0.78-0.92). There was no statistical difference in the percent HPV positive for each sample (p = 0.30). HPV testing of the dry sample had an 88.5% (95% CI: 79.9-94.3%) sensitivity for HPV detected using the wet specimen. For the HPV results categorized hierarchically, there was 92.8% overall agreement and a kappa of 0.87 (95% CI = 0.80-0.93) for the paired results.

Conclusion: Using dry flocked swabs to collect cervical cells is a valid alternative to collecting wet samples for HPV DNA testing using a PCR based test.