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Dx Focus Apr 7, 2011: Clinical and Regulatory PCR and Nucleic Acid Testing News


UK molecular diagnostics firm Myconostica this week announced the recent publication of positive research results for two of its CE Marked, real-time PCR-based assays for life-threatening fungal infections.

First, a paper published online March 2 in the Journal of Clinical Microbiology presented the results of a multicenter trial of the company's MycAssay Pneumocystis for detecting Pneumocystis jirovecii.

The trial recruited 110 subjects with a variety of underlying diseases and conditions including solid organ transplants, leukemia, solid tumors, and HIV. The study's authors analyzed respiratory bronchoalveolar samples and identified 13 of 14 patients with clinically proven Pneumocystis pneumonia, or PCP. The test gave positive results for nine of 96 patients who did not have PCP at the time of the testing. Subsequently, one of these patients developed PCP while the others were considered to be colonized with Pneumocystis jirovecii.

PCP afflicts both AIDS and non-AIDS patients with mortality rates of more than 20 percent, the company noted. Currently, the infection is diagnosed through microscopy of lung tissue, bronchial lavage, or other deep respiratory samples, and as such a less-invasive test for the fungus is desirable, the company noted.

A second paper published online March 30 in JCM presented results of the evaluation of analytical and preliminary clinical performance of the company's MycAssay Aspergillus test for diagnosing invasive aspergillosis, or IA, from serum samples.

The trial tested 31 high-risk hematology subjects, 10 of which were classified as having proven or probable IA; and 21 of which were at risk of IA, for a total of 170 samples.

The study found the assay to have a sensitivity of greater than 70 percent and specificity of greater than 90 percent. Myconostica noted that this was a retrospective study with stored samples, and as such some degradation of DNA was likely to have occurred. The company said that a prospective study would likely improve on the assay's reported sensitivity.

Myconostica said that traditional methods to identify Aspergillus infection are typically inaccurate, insensitive, and slow, taking up to 10 days for a result. When combined with a suitable DNA extraction system, MycAssay can provide a result within three hours, the company said.

Exiqon this week presented positive data at the American Association of Cancer Research annual meeting in Orlando, Fla., in support of its PCR-based microRNA screening technology as a blood-based diagnostic test for early-stage colorectal cancer.

In a multicenter study, Exiqon has demonstrated the ability of its MiRcury LNA Universal RT microRNA PCR platform to robustly detect miRNA biomarkers associated with the presence of colorectal cancer in less than 0.2 mL of blood.

The first phase of the research program identified candidate miRNA biomarkers in plasma samples from stage II/III colorectal cancer patients and age- and gender-matched colonoscopy-verified healthy controls. A genome-wide screen in blood plasma profiled 730 individual miRNAs from 50 stage II cancers and 50 matched controls. Exiqon used these results to develop a candidate panel of 378 miRNAs detectable in less than 0.1 mL plasma.

In the second phase of the program, Exiqon profiled the candidate panel of miRNAs in a study set of 227 stage II/III colorectal cancer patients and matched controls.

After that study, the company narrowed down the candidate markers to a signature comprising "less than 30" miRNAs, Exiqon's Søren Nielsen said in his presentation.

The results demonstrated that by using an miRNA signature derived from plasma obtained under standard clinical conditions it is possible to detect colorectal cancer.

The study included samples from patients with proven colorectal cancer and matched healthy subjects from five Danish hospitals; and the biomarker signature demonstrated sensitivity and specificity of 75 percent and 80 percent, respectively. Exiqon said these results fulfill the requirements for a commercial test.

The next phase in test development, Exiqon noted, will consist of final assay development and validation of the biomarker signature in a larger study cohort of more than 3,000 patient and control samples. The company said that it plans to publish the results of the validation study before year end.

Exiqon's test profiles microRNA expression by combining the company’s locked nucleic acid technology with a universal reverse transcription step. The use of two LNA-enhanced PCR primers enables quantitation of very low microRNA levels and discrimination between closely related microRNA sequences; while the universal RT step also greatly reduces sample input requirements and technical variation, according to the company.

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