Vaginal symptoms are one of the most common reasons for women accessing acute healthcare in the USA.1 Vaginitis is most commonly evaluated based on clinical observations, including assessment of discharge characteristics, vaginal pH and, in some settings, microscopic examination of vaginal fluids. However, many women are suboptimally treated and often seek additional healthcare within the next 90 days.2 A substantial reason for this includes the common occurrence of multiple pathogens but treatment of only a single organism.3,4 Clinical assessment of signs and symptoms of vaginitis have been demonstrated to be inaccurate when a single organism is present and even more so when multiple organisms are contributing to the syndrome.5 As a result of our improved understanding of the multifactorial causes of vaginal symptoms and the poor accuracy of clinical assessment for disentangling the presentation of disease, laboratory diagnostic tools are needed to improve care for women with vaginitis.
Newer diagnostic assays offer solutions to improve the detection of causative agents of vaginitis and thus provide the opportunity to more accurately treat women and potentially reduce the need for follow-up healthcare visits. While several point-of-care (POC) options exist, they are associated with low accuracy or high cost. Molecular lab-based testing can reduce the cost, compared with POC tests, and improve diagnostic accuracy with a turn-around time that supports rapid adjustment (within a day or two) of clinical management decisions when appropriate. One such assay is the BD Vaginal Panel (BDVP) (Becton, Dickinson and Company, BD Life Sciences – Integrated Diagnostic Solutions, Sparks, MD, USA). This molecular assay detects several organisms associated with bacterial vaginosis (BV), several species of Candida (including C. albicans, C. glabrata, C. krusei and other species) and the sexually transmitted pathogen Trichomonas vaginalis.
BD MAXTM Vaginal Panel Assay and the BD CORTM system
The BDVP was developed for use on the BD MAXTM System (MAX; Becton, Dickinson and Company, BD Life Sciences – Integrated Diagnostic Solutions, Sparks, MD, USA), which uses unitized (one strip per sample) reagent and consumable strips for specimen processing with subsequent real-time polymerase chain reaction (PCR) performed on microfluidic cards for the detection of targets with fluorescence output to indicate the presence of those targets. The MAX system is a bench-top analyzer that can perform 24 tests per run, in approximately 3.5 hours, making it ideal for laboratories with low volume testing needs. The MAX system can also be used to perform a broad number of tests including a sexually transmitted infection (STI) panel, a respiratory panel and two enteric panels as well as other pathogen detection assays.6–13
In response to the need for higher throughput in some settings the BD CORTM System (COR; Becton, Dickinson and Company, BD Life Sciences – Integrated Diagnostic Solutions, Sparks, MD, USA) was developed. This unique platform can perform 96 tests in a single run using MAX technology, but can simultaneously detect and genotype human papilloma virus (HPV) using the OnclarityTM HPV assay (Becton, Dickinson and Company, BD Life Sciences – Integrated Diagnostic Solutions, Sparks, MD, USA), a PCR assay that was first approved for use with the BD ViperTM LT System (Becton, Dickinson and Company, BD Life Sciences – Integrated Diagnostic Solutions, Sparks, MD, USA).14 The Onclarity assay on the COR instrument uses the same chemistry and sample processing methodology as the Onclarity assay on the Viper LT instrument.15 Thus, with the dual capacity to run two different PCR processes simultaneously, the COR system creates a laboratory solution that supports testing for multiple conditions on a single platform with the use of reagents and consumables in a variety of settings.
The COR is fully automated, combining all steps of specimen processing, amplification and detection on board the instrument. The system utilizes random access, allowing the user to load samples as they arrive in the lab and order any of the approved assays with batching managed internally. The use of unitized strips, common reagents and amplification parameters are unique features of the system that support random access to a broad menu with minimal reagent waste. Furthermore, the assay accepts multiple specimen types stored in diverse transport media, including vaginal swabs in sample buffer tubes (SBT) (Becton, Dickinson and Company, BD Life Sciences – Integrated Diagnostic Solutions, Sparks, MD, USA) that can be used for both BDVP testing and the BD CTGCTV2 (BD STI) panel. For HPV testing, the assays on board have claims for cervical brush diluent tubes (Becton, Dickinson and Company, BD Life Sciences – Integrated Diagnostic Solutions, Burlington, NC, USA), primary liquid based cytology (LBC) vials, BD SurePathTM (Becton, Dickinson and Company, BD Life Sciences – Integrated Diagnostic Solutions, Burlington, NC, USA) and Hologic PreservCyt® (Hologic, Inc. Marlborough, MA, USA), as well as manually aliquoted LBC specimens.16
The COR system comprises three modules: the pre-analytical processing PX module, the GX module that performs the Onclarity assay for HPV detection and genotyping, and the MX module that utilizes MAX technology for detection of other infectious diseases, including the BDVP and STI panel that detects Chlamydia trachomatis, Neisseria gonorrhoeae and T. vaginalis. The automation of the PX module includes uncapping and recapping of specimens, which is a source of repetitive motion injury for many laboratorians, control preparation and specimen batching. For the BDVP assay, the PX instrument scans the barcode on the sample buffer tubes, creates a batch and vortexes them. Next, the sample buffer tubes are placed by the instrument into racks which are moved to the MX instrument. The MX transfers a rack to the processing deck and takes a sample aliquot from each tube. The MX extracts nucleic acid, loads extracted nucleic acid into a cartridge, and moves the cartridge into the MX reader. The MX reader performs amplification and detection for the assay. The COR software processes the results, creates reports and sends to the laborarory interface system (LIS) software. With the capacity to perform 96 tests in ~3 hours, over 300 results can be generated per 8-hour shift.
For the BDVP, results are reported as BV positive/negative, Candida spp. positive/negative, C. glabrata positive/negative, C. krusei positive/negative and T. vaginalis positive/negative. For BV, the system software performs bioinformatic analysis to assess the relative abundance of amplified DNA from Lactobacillus spp., including L. crispatus and L. jensenii (expected to be in low abundance) and bacteria associated with BV, including Gardnerella vaginalis, Atopobium vaginae, Megasphaera-1, and bacterial vaginosis associated bacterium type 2 (BVAB-2) (expected to be in high abundance) in order to call a positive reaction.17 For Candida, if any of C. albicans, C. tropicalis, C. parapsilosis or C. dubliniensis are detected above a clinically relevant cutoff point, the Candida spp., result is positive. These species are grouped together based on the relatively infrequent identification of non-albicans species in the general population. C. glabrata and C. krusei results are shown separately due to different treatment and management requirements if either of these pathogens is detected.17 T. vaginalis is labelled positive or negative based on the presence or absence of a single T. vaginalis gene target. The target is the same as the one used in the BD STI assay. The BDVP has excellent performance characteristics when compared to standard of care diagnostics, culture and Nugent criteria for BV. For BV, Candida and trichomonas, the sensitivity estimates of the assay were 90.5%, 90.9% and 93.1%, respectively.17 Given the lack of a strong standard for comparison, these estimates are likely to be conservative.
Use of the BD COR System enables clinicians to offer symptomatic women comprehensive care while requiring only a single vaginal sample by performing the BDVP and BD STI tests at the same time. The BDVP and STI assays are performed as described above with an additional round of identical steps for the STI panel. After the PX scans the barcode on the sample buffer tubes, it creates both a BDVP batch and an STI batch order for all samples requiring dual testing. The sample aliquoting steps are performed twice and the aliquots for each assay are moved through the system. The MX extracts nucleic acid in separate sections of the deck for each of the assays, loads extracted nucleic acid into separate cartridges and moves the cartridges into separate MX readers. The respective MX readers perform amplification and detection for each assay and the system software processes the data, creates reports and sends them on to the LIS. Thus from a single vaginal sample, BDVP and BD STI results are generated in parallel with no additional hands-on time of user interface requirements.
Discussion
From a laboratory perspective, the COR system can be used to support women’s health by supporting HPV screening of women seeking routine healthcare, as well as a diagnostic test for women with vaginal complaints using a single, fully automated platform. Including the BD STI panel with the BDVP assay will ensure comprehensive care of women. Given the high prevalence of T. vaginalis, and the shared mode of transmission of this pathogen, simultaneous testing for Chlamydia trachomatis and Neisseria gonorrhoeae is reasonable since women exposed to one STI may be exposed to all STIs. Studies have shown that up to 15% of women seeking care for vaginal complaints have a detectable STI when molecular diagnostics are utilized.18 This proportion increases to nearly 25% when considering only women with BV.
Future studies should focus on the health economics of utilizing such a platform, as well as the impact of utilizing molecular tools for both cervical cancer screening and for the highly accurate identification of the multiple causes of vaginal complaints that cause a high number of healthcare visits, including a potentially avoidable number of return visits for unresolved symptoms. A highly automated system can provide many laboratory efficiencies and data are needed to support adoption of such platforms.
