Sputasol (Dithiothreitol 0.54%) Improves the Detection of Human Papillomaviruses Using the Cobas 4800 System

Dear Editor, Persistent infection with human papillomavirus (HPV) is the main cause of cervical cancer. Screening of cervical specimens for high-risk human papillomaviruses (HR-HPV) has become a routine part of patient care in most countries. The Roche cobas 4800 system (Roche Molecular Systems Inc., Pleasanton, CA, USA), a fully automated system that uses in vitro qualitative realtime PCR technology, displays high sensitivity and specificity for HR-HPV detection [1]. However, a small proportion of invalid results may occur in specimens showing mucopurulent discharge because of pipetting errors, clot formation, or failed amplification, which could cause a delay in the results and lead to additional waiting time for patients and extra work hours for staff, although most cases are resolved by vortexing the specimens and retesting. To the best of our knowledge, no researcher has tried to overcome this problem by pretreating specimens with an appropriate concentration of Sputasol (Oxoid Ltd., Basingstoke, United Kingdom); Sputasol (dithiothreitol 1.4%) has been used to aid culturing and DNA extraction from sputum specimens in some laboratories [2]. Here, we propose a standard method to improve HR-HPV detection without affecting the performance of the cobas 4800 HPV system. The cobas 4800 HPV system comprises a cobas x480 instrument (for specimen preparation) and a cobas z480 analyzer (for real-time PCR). The cobas 4800 HPV test is available on the cobas 4800 system that can detect 14 HR-HPV types (16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, and 68). The cobas 4800 system software automatically displays reportable results as negative, positive, or invalid. Prior to the study, written consent was obtained from all of the patients enrolled and institutional review board approval was also obtained. Twenty cervical specimens, which might have failed the test or been reported invalid because of visible quantities of cervical mucus, were prepared for the study. Each specimen was aliquoted into three 13-mL round-based secondary tubes for three different tests. The first set of tubes served as the control group, and remained untreated (test 1). The second set of tubes was vortexed for 1 min before testing (test 2). The third set of tubes was pretreated with an appropriate concentration of Sputasol (dithiothreitol 0.54%) and then vortexed for 1 min before testing (test 3). In our study, a problem of excess mucus was deemed resolved if a valid result was obtained from the cobas 4800 system. As shown in Table 1, invalid results were indicated by errors on the cobas x480 instrument (X3 or X4). Our results indicated that the percentages of resolved specimens were 5%, 70%, and 100%