Researchers say Mobidiag’s microarray-based diagnostic test technology looks promising
There’s a new DNA-based microarray platform that could speed identification of blood-borne pathogens. By allowing clinical laboratories to deliver test results in just 18 hours, use of this new microarray could improve early detection and management of sepsis patients.
In a study headed by Päivi Tissari, M.D., of the Division of Clinical Microbiology, Helsinki University Hospital Laboratory in Finland, the Prove-it sepsis assay, manufactured by Helsinki-based Mobidiag, demonstrated 94.7% clinical sensitivity, 98.8% specificity, along with 100% sensitivity and specificity for methicillin-resistant Staphylococcus aureus bacteremia. The conventional process of growing a culture—the medical laboratory’s gold standard—typically takes between one to three days to become positive and two more days to identify the bacteria and their antibiotic sensitivity patterns. Mobidiag’s Prove-it sepsis assay returns results in only 18 hours.
Tissari’s study was published in the December 10 issue of The Lancet. It involved 3,318 samples taken from patients with suspected sepsis, of which 2,107 were positive. Samples were analyzed with the conventional culture-based method and the Prove-it sepsis assay.
In October, Mobidiag announced that this diagnostic product was cleared for sale in Europe. The Prove-it diagnostic test system is a CE-marked product for In Vitro Diagnostics (IVD) of sepsis.
The technology involves a novel polymerase chain reaction (PCR) and microarray process based on amplification and detection of the 50 most common gram-negative and gram-positive bacterial species. PCR enables researchers to produce millions of copies of a specific DNA sequence in just two hours, bypassing the need to use bacteria to amplify DNA. “It also indicates meticillin resistance by detection of the mecA gene sequence and differences between Staphylococcus aureus and coagulase-negative staphylococci,” note the researchers.
Researchers involved in the study noted that the array’s design is flexible, which means the pathogen screening technology can be use to detect other microorganisms and molecular indicators of resistance. For example, the assay has been configured to detect fungi, which is important due to the increasing prevalence of fungaemia in the United Kingdom (UK), particularly Candida. Candida is involved in three to five cases of sepsis per 100,000, which represents a 40% rise over five years. Tissari points out that, were labs to be able to identify candida to the species level in two hours, that would speed up use of evidence-based therapies—and often cheaper antifungal medication—than might not otherwise be used.
The study authors also pointed out that Mobidiag’s diagnostic microarray platform could potentially be used to detect other microorganisms that cause malaria, leishmaniasis, trypanosomiasis, and toxoplasmosis, because conserved and variable region genes for each organism have now been identified. The research team is also investigating use of the sepsis platform for other biological specimens from patients with sepsis, including pus from empyemas, joint infections, and abscesses; purulent cerebrospinal fluid; bone-marrow aspirates; and pericardial exudates.
Anticipating wide use of this microarray technology by clinical laboratories once regulatory clearance has been obtained, the researchers noted: “Early knowledge provided by this new diagnostic platform could be easily integrated into everyday laboratory workflow in primary- and secondary-care settings…”
Of interest to pathologists and clinical laboratory managers was the acknowledgement by the researchers that the Prove-it sepsis assay would increase laboratory costs. But they observed that the trade-off would be significant savings from the much lower costs associated with the benefits of an early and accurate diagnosis and more appropriate disease management, including targeted investigation, hospital length of stay, and outcomes for the patient.
This new laboratory test technology will serve a large market. “About 20 million cases of severe sepsis arise every year worldwide, and sepsis accounts for up to 135,000 deaths in Europe and 215,000 in the USA yearly, despite availability of effective antibiotics,” wrote Tissari in the study published by Lancet.