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Molecular diagnostics (MDx) is one area in the clinical laboratory showing no signs of slowing down after years of remarkable growth, expansion and implementation. Molecular applications most frequently include infectious diseases, genetic disorders and cancer testing, and have been life-changing for laboratorians--and life-saving for patients.
MDx platforms are no longer found only in esoteric labs, giant hospital labs or within facilities considered thought-leaders. MDx--and the plethora of detailed information it can provide--is truly accessible for labs of any size and type. And, as the technology advances, so too do the ways in which MDx is used to identify disease and monitor treatment.
 Embracing MDx
"It's safe to say most clinical labs are aware of what's going on in molecular testing," affirmed Gregory J. Tsongalis, PhD, HCLD, FACB, director, Molecular Pathology; acting director, Clinical Chemistry; co-director, Pharmacogenomics Program; and associate professor of Pathology at the Dartmouth Medical School at the Dartmouth Hitchcock Medical Center, Lebanon, NH. The majority of mid- to large-sized hospital labs are performing some type of MDx; the smaller labs that aren't doing anything internally are sending it out to reference labs, so they're cognizant of what's available, at least on a basic level.
That means the big push is to get smaller and some mid-sized labs to adopt molecular testing. For that to happen, Dr. Tsongalis said, platforms must continue to move toward automation. "There are already some good choices out there," he said, "and we're going to see a big expansion in that area."
The next generation of MDx analyzers, then, should incorporate easily into the existing lab and lab workflow and provide a complete sample-to-answer system that is easy to learn, easy to use and highly reliable. They will also have to accommodate a broad menu, including the most common, high-volume tests, like Ct/Ng, HPV, MRSA, HIV, HCV, factors V and II. A broad menu will enhance reimbursement opportunities and reduce costs associated with send-out testing, noted Thomas Pribyl, PhD, group manager, Technical Marketing for Molecular Diagnostics, Beckman Coulter Inc., Fullerton, CA.
Labs hesitating to implement MDx regularly cite cost as a barrier; they fear test volumes won't justify bringing a test in-house. But after implementation, Dr. Tsongalis said, the volumes always go up compared to what you've projected. "I've had physicians tell me over and over that they haven't ordered things before because it was a long turnaround time, but when it's in-house, they'll order it."
To ensure this is the case, laboratorians should be proactive and inform physicians of new tests and what they can do--then be available when the phone call comes asking for advice on how to interpret a result. "We need to go back to being clinical consultants," Dr. Tsongalis asserted. "Labs have shied away from that."
Better, Faster, Smaller
"In the realm of infectious diseases, with the exception being when there's an outbreak, applications are no longer novel," Dr. Tsongalis said. "We've done just about everything we can--we're just trying to do it faster and cheaper."
Thus, now that the technology driving molecular assays is understood and established, the goal is for the next generation of analyzers to offer faster turnaround times with increasingly relevant and detailed information and a smaller footprint. Dr. Tsongalis pointed out that as automation continues to develop, there's no need to keep analyzers sequestered in a specific lab. "That need will be justified only by space, availability of technologists and expertise."
Hence, MDx will continue to move to the point of care (POC), physician office labs and smaller labs that traditionally shy away from esoteric testing. Automated analyzers for molecular testing for infectious disease are available with small footprints and minimum hands-on time, allowing them to be placed where they're needed the most. Random access, turnkey systems at the POC can offer major benefits in the emergency department or physician office labs.
Of course, Dr. Tsongalis stressed, that's not to say moving MDx to the POC will render the central lab obsolete or unnecessary. Having multiple setups throughout a large hospital or health system, for example, can be more costly than one comprehensive MDx system in the central lab. Options exist for any situation in any kind of facility.
What's more, Dr. Tsongalis discourages laboratorians from looking at achieving "ultimate automation" as the end-all for molecular testing. "I remind everyone we have fully automated chemistry and hematology labs," where laboratorians are still needed--perhaps just in more of a troubleshooting role. "People still have to understand what's going on and what's happening in these boxes to have a successful lab."
MDx in the Blood Bank
Many in the clinical lab industry are now comfortable with discussing MDx in terms of infectious disease, oncology and genetic disorders. But molecular applications also have important implications for transfusion medicine. Greg Denomme, PhD, FCSMLS(D), director of the Immunohematology Reference Laboratory at the BloodCenter of Wisconsin, Milwaukee, said three new molecular assays--Dombrock, Lutheran and Kell (Js) genotyping--may help clinicians determine the root of adverse reactions to blood transfusions.
Having these tests available on a molecular platform is important because while blood group antigens were historically detected using specific antibodies, reliable antisera are often in limited supply for the antigens of Dombrock, Lutheran and Kell (Js), Dr. Denomme explained. Additionally, adverse reactions to these antigens typically develop after multiple transfusions, at which point the ability of antibodies to detect the patient's antigens is restricted.
"With the development of molecular tests using genomic DNA extracted from a blood sample, these antigens are predicted on the basis of the inherited genes; previous transfusions do not affect the test results," Dr. Denomme explained. "The laboratory uses fluorescent hydrolysis probe technology to determine antigen status. The advantage here is in its versatility. Assays can be performed in single or small batch mode and are easily transferred to high-throughput automated platforms."
Soon, these tests will be used not only for determining the source of adverse reactions, but also for blood donor screening at the BloodCenter of Wisconsin. "As more antigens are identified," Dr. Denomme said, "large numbers of donors will need to be screened to find matches."
Predicted Expansions
One survey of clinical labs in the United States estimates more than 52 million MDx tests were performed in 2008--93 percent in infectious disease testing, five percent for genetic disorders and two percent related to cytogenetics, cancer and HLA typing applications [Molecular Diagnostics Survey 2009: A Report on the Status of the U.S. Market. Enterprise Analysis Corporation. Available at: www.eacorp.com/2009_MDS/eac_2009_mds_table_of_contents.pdf. Last accessed Dec. 15, 2009.]. The expansion of cervical screening for HPV infection is a powerful driver of these numbers; 88 percent of the total test volume in the United States is for Chlamydia/gonorrhea, HPV, HIV and HCV.
Infectious disease testing has--and will continue to be--a huge segment of MDx. Hospitals continue to implement screening programs for MRSA and other hospital-acquired infections; the potential comeback of H1N1 influenza during "regular" flu season must be considered.
The survey also estimates 2.5 million tests performed in 2008 for genetic disorders, most commonly cystic fibrosis and thrombophilia. The growth in genetic testing is slower than in infectious disease testing, but as more genetic mutations related to specific diseases are uncovered and pharmacogenetic tests continue to emerge, genetic testing will expand.
Kelly J. Graham is on staff at ADVANCE.
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