We believe there is additional information readers should know when assessing the conclusions drawn in this article. First, the sensitivity of the Detect-Ready MRSA Panel reported in this study is much lower than the sensitivity reported in all other studies with the Detect-Ready MRSA Panel. The authors of this paper acknowledge this fact. However, more is known about this anomaly in performance results than the authors chose to include. The omissions have been discussed at length with the authors, were acknowledged by the authors, and were fully credited by the authors in a previous public presentation of this material. The fact that this information is completely absent from this article undermines its accuracy and utility.

We worked closely with the authors during the design and conduct of this study. In response to the higher-than-expected number of false negative results generated by the Detect-Ready MRSA Panel in the study, we undertook an investigation into the possible causes. Our researchers found that 7 of the 11 samples reported as MRSA false negatives were tested using a single batch of PCR mastermix, which on retesting showed an unexpected deterioration in performance in two of the four amplification reactions in the PCR.

We informed the authors about the results of these investigations prior to any public presentation of this material. In response, the authors included a written report on, and acknowledgment of, the results of our investigations when they presented the same data earlier this year as a poster at the 22nd European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) meeting on April 23, 2012. Yet despite having publicly acknowledged the issue at ECCMID, the authors omitted it entirely from the discussion in this paper. We believe that considerations of accuracy, good scientific method and transparency make it essential that the authors include this information—that the effect of a known product performance issue from a single batch of PCR mastermix was a probable cause of the unusually low sensitivity of the assay in this study. The EECMID poster included the following language added by the authors:

“The manufacturer of the Detect-Ready MRSA Panel has investigated why the sensitivity of the assay reported in our study was significantly lower than the normal sensitivity of at least 98%. Their investigation reported that 7 of the 11 samples reported as false negative for MRSA were tested with the same batch of PCR Reaction Tubes, which on retesting showed significant deterioration in performance in two of the four channels used by the assay. The cause of the failure of one batch of PCR Reaction Tubes has been identified and corrective actions implemented, which include a follow up study performed by our laboratory.”

As soon as the cause of the reduced product stability affecting this batch was identified, corrective actions were implemented. A follow up study performed by our laboratory then confirmed that the problem was limited to the one batch, and our previous performance levels are again consistently being achieved. Corrective actions included permanent changes in aspects of our production process to ensure this problem does not re-occur.

In view of this situation, we believe that this study as published by PLOS is not an accurate representation of the performance of the Detect-Ready MRSA Panel.

Tzvi Tzubery, Ph.D.
Director of Research and Development
Molecular Detection Inc.