CONTINUING EDUCATION :: WOMEN’S HEALTH


Now, the advent of sample-to-answer molecular di- agnostic systems — instruments that handle everything from sample preparation and pre-analytics to analysis and reporting results with minimal intervention from clinical lab members — offer a new approach to molecular diag- nostics for this type of maternal/fetal or mother/newborn testing. These streamlined systems make it easier for even small clinical laboratories to expand their test menus and introduce women’s health testing in a feasible and cost- effective manner.


Why molecular diagnostics matter For as long as any current practitioner can remember, cul- ture-based testing has been considered the gold standard for diagnosing most infectious diseases. It’s inexpensive, does not require advanced training, and has the advan- tage of being familiar to pathologists and laboratorians worldwide. After all, direct observation of an organism provides a definitive result. So why look for alternatives to a testing methodology that has served us well for more than a century? Culture’s one great weakness: time. While culture-based tests generally give reliable results, they do so at their own pace, which is not necessarily in-line with the pace of healthcare. Typical cultures might generate results in 48 hours; with certain slow-growing pathogens, results may take weeks. When additional cultures need to be added, such as for antibiotic susceptibility testing, answers often cannot be produced quickly enough to make a difference in the treatment of a patient. Fortunately, speed is where molecular diagnostics shine.


These tests do not require growing microbes over time; they simply detect and quantify the nucleic acids present in a sample, allowing for diagnosis of known — and sometimes even novel — pathogens based on their DNA or RNA signatures. Depending on the test, results may be generated in an hour or just a few hours. Typically, molecular diagnostics can achieve excellent sensitivity and specificity because of their genomic foundation. Across many clinical testing indications, molecular diagnostics


(often called NAATs for nucleic acid amplification tests) are now included in diagnostic guidelines alongside stalwart methods like culture. In some cases, particularly viral detection, molecular diagnostics have actually supplanted culture to become the recommended laboratory method to aid in diagnosis. Another reason for the increasing use of molecular diag- nostics is their flexibility for expansion. The conserved DNA or RNA genomic targets or signatures of multiple pathogens can be combined in a panel test, allowing laboratorians to test for several of the most common culprits in a single assay. This streamlined approach is instrumental when symptoms of infection overlap, such as testing respiratory infections or gastrointestinal infections. The panel-based approach delivers answers for all pathogens together quickly, while serial testing for each pathogen could drag on for days. Below, we will review molecular diagnostics in the context of testing for HSV1 & 2, GBS, and CMV.


HSV testing The herpes simplex virus is one of the most pervasive human pathogens, globally. HSV1, primarily transmitted through saliva, causes both oral herpes (recognizable through telltale cold sores) and genital herpes. HSV2 is sexually transmitted and causes genital herpes as well as oral herpes. According to estimates from the World Health Organization, some 67% of adults under the age of 50 — that’s 3.7 billion people — have


Screening for CMV is not yet universally recommended, even though congenital infections pose a serious health risk for newborns.


acquired HSV1, while more than 490 million people from 15 to 49 years of age have HSV2.1


Both types of HSV lead to lifelong infections, but in many


cases, people are asymptomatic and never realize they have the virus. Those who develop symptoms may experience epi- sodic mucocutaneous or cutaneous lesions, or even fulminant encephalitis. In developing babies, exposure to either type of HSV could lead to a dangerous central nervous system infection; left untreated, the infection can be fatal. HSV can be passed by the mother to the infant during birth, or less commonly, in utero or after birth.2-4 For these reasons, it is essential to understand the risk of a mother passing either type of HSV to her baby, particularly if the mother experiences her primary infection while pregnant or has an active outbreak at the time of birth. If a pregnant woman exhibits lesions associated with herpes infection, she should be tested for HSV1 and HSV2. In some cases, it can be challenging for clinicians to distinguish between herpes lesions and lesions from other infections, such as syphilis or varicella- zoster virus (VZV) making panel tests that cover some or all of these pathogens in one assay useful for a definitive diagnosis. The ability to test for several infectious etiologies simultane-


ously is one reason that molecular diagnostics are a good fit for HSV1 & 2 testing. Another is speed. Culture-based testing for these viruses typically takes a minimum of two to three days, the ability to maintain mammalian cell-culture lines and specialized staff, while commercially available molecular diagnostic tests can generate highly accurate results in just 60 minutes. That kind of turnaround time may not be essential for the mother, but every minute counts for a potentially infected baby. When doctors know that a mother had evidence of an active HSV infection while giving birth, they can immediately test the newborn. Comprehensive testing may include “surface specimens” which include eye, mouth, nose and anal swabs as well as swabs of any skin lesions if present, whole blood, and a lumbar puncture to check the cerebrospinal fluid for the presence of the virus.5


Rapid molecular diagnostics can provide


results for all of those samples in an hour, but it is important to select a platform that can be used with all sample types.


MLO-ONLINE.COM MAY 2022 9


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