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94 Executive Briefing a hospital lab using an enzyme immunoassay to detect C. difficile infections may only identify six out of 10 patients with the infection. A study in JAMA Internal Medicine suggests the high sensitivity of molecular testing can produce too many false positive results. However, these types of false positive diagnoses can be avoided from the beginning with the aforementioned appropriate sam- ple testing and adequate discussions regarding patient history. "Basically you can't just use the test alone in making the diagno- sis. The test has to be used in conjunction with patient symptoms, patient history," Dr. Peterson says. "If you aren't careful with who you test, you will think you have a lot more C. difficile infections than you do. That's not a problem with the test; it's a problem with physicians not asking enough questions and taking enough time to make sure their patient that has the symptoms actually has a C. difficile infection." In fact, experts suggest the high sensitivity is an asset to PCR testing. Roche's Dr. Newhouse says this sensitivity is the No. 1 benefit of their molecular test. "It means for sure you're missing fewer patients." Sensitivity, Specificity and the Cost of a Diagnosis While a test's sensitivity rate measures the true positive rate of a diagnosis, specificity measures the true negative rate, or how often a test produces a negative diagnosis for a patient who in fact does not have an infection. Dr. Newhouse notes that, along with its high sensitivity, the co- bas Cdiff test also has a high specificity, which means it produc- es fewer false positive results than tests with a lower specificity. A positive C. difficile diagnosis is challenging for patients and can take an emotional toll on them, so he says it's critical to ensure that positive diagnoses are accurate. "There are a lot of implications for patients when they're called positive," Dr. Newhouse says. In addition to starting a strong an- tibiotic regimen, patients diagnosed with C. difficile are gener- ally placed in full isolation and contact precaution to stop the spread of infection to others, which requires anyone entering the patient room to be fully gowned. Additionally, the number of visitors allowed is restricted. "There's this emotional trauma because they do feel isolated when they're really sick and they get fewer visitors and fewer nursing staff going into the room," Dr. Newhouse says. "You want to have a highly specific test to know you're accurately treating only those patients you're supposed to be treating." Isolation precautions require extra gloves and gowns for clini- cians, as well as a special cleaning protocol, which incurs extra costs for the hospitals. By minimizing the chance of producing a false positive diagnosis requiring this extra level of care, hospi- tals can avoid paying for any unnecessary use of these products. Reducing Human Error Automation is another advantage of molecular testing, as it re- duces the number of human touchpoints in the lab. The han- dling, processing and loading of test samples into the traditional immunoassay cartridges introduces opportunities for human er- rors to skew test results, especially if using a pipette is required. Dr. Newhouse explains, "The cobas Cdiff test drastically mini- mizes the amount of manual handling required to run the test. When a stool sample comes into the lab, the technician simply has to take a swab, dip it in the stool sample, transfer it into the cobas PCR Media tube, vortex and then load that tube directly on the system." "There are no pipetting steps, no manual intervention on the part of the lab technician," says Steven Cagas, PhD, scientific affairs manager within the department of medical and scien- tific affairs at Roche Diagnostics. "That's a big benefit because it does reduce the number of possibilities of human errors in two ways." Dr. Cagas says automation reduces the possibility of cross-contaminating other samples and contaminating the lab space itself. Benefits of Timely Testing Timeliness is critical when it comes to diagnosing C. difficile; an early, accurate diagnosis has implications on patient safety, care quality and costs. According to Roche, the cobas Cdiff test produces test results in just three hours, which means labs can run multiple tests a day and release results relatively frequently throughout the day. Unsurprisingly, the earlier a clinician diagnoses and starts treat- ment for a patient with a C. difficile infection, the greater the likelihood for a positive patient experience and outcome. "The quicker they get that patient off isolation and start treat- ment earlier, it's a benefit to the patient and [reduces] the overall burden to the healthcare institution," Dr. Arcenas says. "If you don't start treatment sooner, they're probably going to be in the hospital longer, have a longer length of stay. That patient is oc- cupying a bed. There's a whole domino effect." Final Thoughts The advantages of molecular testing are numerous — high sen- sitivity, specificity, automation and quick turnaround time. And while other C. difficile tests like enzyme immunoassay offer some of these benefits, Dr. Cagas notes that each individual as- say generally only offers one or two. "You'll either have good specificity, good sensitivity or a rapid turnaround time," he says. "But with PCR-based molecular assays like the cobas Cdiff test, you get all of those combined." n Sponsored by: From research to lab tests to personalized healthcare, Roche touches the entire spectrum of diagnostics. Our focus is doing now what patients need next by delivering innovative healthcare solutions. A leader in the management of infec- tious diseases, Roche Diagnostics offers award-winning services and a comprehensive IVD portfolio with applications in HAIs, virology, women's health, blood screening, genomics and oncology. We are committed to working with our lab and clinician partners to help improve the management of disease, one patient at a time.