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SPECIAL FEATURE :: STIs Prevention of STIs


Education and prevention are key pillars in the effort of con- trolling the STI epidemic. While this effort is vital, it must be fortified by accurate diagnostics and treatment. Prior to the advent of polymerase chain reaction (PCR) technology, microbiological culture methods were the preferred method of diagnostics. Following Koch’s postulates, cultures were/are deemed in many cases as the true test for isolating a pathogen and implication as the causative agent of disease. Diagnostic culture tests served the clinical community for quite some time. However, microbiological culturing is time consum- ing as laboratories and diagnostic providers must culture the pathogen in an appropriate growth medium. Therefore, diag- nostic culture tests take time and require skilled microbiolo- gists to conduct tests and report accurate results. The need for better diagnostics led to the introduction of ligase chain reaction test10


for detection of chlamydia with


better sensitivities and specificities than culture or direct fluorescent-antibody assays. The advent of nucleic acid ampli- fication tests (NAAT) with its high specificity and sensitivity brought about remarkable changes in the clinical diagnostic space. The introduction of PCR based CT/NG testing, along with screening guidelines to test for infections, brought a paradigm shift in the diagnostic space. The testing times were dramatically reduced, with results available in a few days instead of weeks. Screening also allowed the identification of asymptomatic infected individuals, which in the case of STIs, is the clear majority of infections.


From necessity sprang the creation of a whole new genera- tion of diagnostic tests now classified as point of care (POC).11 These diagnostic tests do not need to be done in traditional hospital laboratories and can be housed in clinics and near- patient settings. The POC tests allow for rapid test results often under an hour albeit without the remarkable specificity and sensitivity of NAATs. POC testing is advantageous as it allows for the rapid identification of the causative organism, especially in case of syphilis. In addition, this is a great tool in settings where the risk of losing patients to follow up is high. However, most POC testing modalities are restricted to a single test. Complex STIs, which could have multiple caus- ative agents, could be a potential hurdle for POC testing. POC tests are designed for near-patient settings, which limits the ability to do large volume testing as compared to the tradi- tional laboratory instruments. From an operational perspec- tive, a lab would benefit from minimal interactions with the large number of samples in a national screening/diagnostic program.


STI screening and testing


A national screening program for STIs like CT, NG, TV, MG, or HPV would involve large numbers of samples. Testing for STIs is a challenge for diagnostic manufacturers for a variety of reasons, at the forefront is the myriad of sample types that could be utilized. The sample types differ with respect to gen- der and anatomical sites. Furthermore, for certain STIs, there is a lack of consensus on the appropriate sample type that can/should be used in a screening assay. Screening/testing urogenital specimens for CT/NG/MG could result in missing many infections as a significant percent are rectal and oral infections, especially in high-risk populations. There are no FDA-approved tests for testing extra-genital specimens, how- ever, there are multiple validated lab developed tests (LDTs). Diagnostic test providers have specific swabs for collecting specimens from the vagina, endocervix, throat, and a sepa- rate collection device for urine. For cervical cancer screening,


32 MAY 2019 MLO-ONLINE.COM


liquid-based cytology (LBC) devices utilizing a cervical brush or broom is preferred. Laboratories must train healthcare professionals on different collection devices to ensure the appropriate device is used to collect specimens for the vari- ous assays. This obviously brings logistical challenges, con- sidering the number of specimens that need to be collected.


Self-collection specimens In recent years, screening programs have realized the importance of including individuals that do not turn up for screening or are unresponsive to invitations for testing. The solution to this challenge seems to have an option for specimen collection at home—wherein, individuals receive specimen collection kits at their residence, they self-collect specimens and mail it to the testing site. Evidence from vari- ous studies12


indicate that individuals are receptive to this


approach and it could include individuals unresponsive to participation in the screening program. The singular collec- tion device would be ideal for specimens collected at home and healthcare premises. The universal collection device would make collections and testing seamless for laborato- ries, with less specimens rejected due to incorrect specimen collection. Considering the large numbers of specimens collected in this universal collection device, specimens after accessioning and without additional processing could be placed on the diagnostic instrument. The instrument would be able to sample through a pierceable cap for testing and report results.


STI assay development challenges


STI assays would be the next logistical challenge for laborato- ries and physicians. One could consider an assay that could test for the most common STIs that have the highest inci- dence. Rather than an all-encompassing microbial panel the assay would be specific to the microbes that cause the most harm (e.g. CT, NG, TV, MG). This assay combination with chlamydia (the most common STI), TV (that has a prevalence of 2.3 million in women aged 14-49)2


increase of 67 percent), and MG (the second most common cause of nongonococcal urethritis).13,14


, NG (which saw an Testing for these STIs


in a single test and rapid reporting of results could enable a physician to instill a treatment program based on etiology rather than observed symptom(s). If the physicians could get results in a time frame that allowed the individual to wait for the correct prescription, it would not only ensure that appro- priate treatment is provided, but also open the conversation for partner notification and treatment. This is a vital cog in the wheel to prevent the of spread of infection, as partner notifications tend to get lost in the testing algorithm or occurs later in the process. This delay in partner treatment is part of the reason why STIs continue to spread.


An additional factor would be offering physicians the option for testing any combinations of the STIs mentioned, as appropriate to their geographical locations. Considering the symptoms manifested by CT, NG, TV, and MG are overlap- ping, it would be pertinent to have an assay that identifies the causative organism(s). Additionally, labs could contrib- ute to epidemiological surveillance by identifying increased incidence rates of an infection in real time, a function that public health labs are required to do. In the age of big data, this could be handled by diagnostic instruments with soft- ware features providing reports on infection rates for set time periods. This would enable each lab testing for STIs to provide real time incidence rates from their geographical locations thereby enabling a faster response by public health agencies.


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