Comparison of the Luminex xTAG RVP Fast assay and the Idaho Technology FilmArray RP assay for detection of respiratory viruses in pediatric patients at a cancer hospital.

Respiratory viruses are increasingly recognized as serious causes of morbidity and mortality in immunocompromised patients. The rapid and sensitive detection of respiratory viruses is essential for the early diagnosis and administration of appropriate antiviral therapy, as well as for the effective implementation of infection control measures. We compared the performance of two commercial assays, xTAG RVP Fast (Luminex Diagnostics, Toronto, Canada) and FilmArray RVP (FA RVP; Idaho Technology, Salt Lake City, UT), in pediatric patients at Memorial Sloan-Kettering Cancer Center. These assays detect the following viruses: respiratory syncytial virus; influenza A and B viruses; parainfluenza viruses 1, 2, 3, and 4; human metapneumovirus; adenovirus; enterovirus-rhinovirus; coronaviruses NL63, HKU1, 229E, and OC43; and bocavirus. We tested a total of 358 respiratory specimens from 173 pediatric patients previously tested by direct fluorescence assay (DFA) and viral culture. The overall detection rate (number of positive specimens/total specimens) for viruses tested by all methods was 24% for DFA/culture, 45% for xTAG RVP Fast, and 51% for FA RVP. The agreement between the two multiplex assays was 84.5%, and the difference in detection rate was statistically significant (P < 0.0001). Overall, the FA RVP assay was more sensitive than the xTAG RVP Fast assay and had a turnaround time of approximately 1 h. The sensitivity, simplicity, and random-access platform make FA RVP an excellent choice for laboratory on-demand service with low to medium volume.

Clinical characterization of human metapneumovirus infection among patients with cancer.

BACKGROUND: Human metapneumovirus is a recently discovered RNA virus that typically causes respiratory disease in children. It has been linked to severe lower airway disease in hematopoietic stem cell and solid-organ transplant recipients. hMPV infection in a large population of patients with underlying cancer and varying degrees of immunosuppression has not been reported. We sought to characterize hMPV infection in patients with cancer. METHODS: Review of all cases of hMPV infection from two seasons (2005-6 and 2006-7) detected by DFA and/or real-time PCR at MSKCC, a tertiary cancer center in New York City. RESULTS: Among MSKCC patients with cancer, 51 (2.7%) of 1899 patients were positive for hMPV, including 3.2% with hematologic neoplasm and 1.7% with solid tumors. More children (4.5%) were positive than adults (2.2%). PCR detected twice as many cases as DFA. Cough and fever were common complaints. The longest shedding period was 80 days. 40 patients received radiographic evaluation; of these, 22 showed abnormalities including patchy (11), ground glass (5), and interstitial infiltrates (4). CONCLUSIONS: hMPV causes a nonspecific respiratory illness and was found in more than 2% of all tested persons with cancer. PCR detected substantially more cases than DFA. Unlike previous reports, we observed no fatalities due to hMPV, including 22 HSCT recipients with the infection.

Experimentally determining the iR drop in solution at carbon fiber microelectrodes with current interruption and application to single-cell electroporation.

Single-cell electroporation uses microelectrodes, capillaries, or micropipets positioned near single, adherent cells to increase transiently the membrane permeability of the cell. The increased permeability permits, for example, transfection without chemical reagents. When using microelectrodes to apply an electric field to the cell, there is a question of how much voltage to apply. Unlike in bulk electroporation, where hundreds of volts may be applied between electrodes, a rather small voltage is applied to a microelectrode in single-cell electroporation. In the single-cell experiment with microelectrodes, a substantial fraction of the voltage is lost at the interface and does not therefore exist in solution. This problem is the same as the classical electrochemist's problem of knowing the "iR" drop in solution and correcting for it to obtain true interfacial potential differences. Therefore, we have used current interruption to determine the iR drop in solution near microcylinder electrodes. As the field is inhomogeneous, calculations are required to understand the field distribution. Results of the current interruption are validated by comparing two independent measurements of the resistance in solution: one value results from the measured iR drop in conjunction with the known applied current. The other value results from a measured solution conductivity and a computed cell constant. We find substantial agreement in the range of resistances from about 2 to 50 kOmega, but not at higher resistances. We propose a simple, four-step plan that takes a few minutes to calculate the approximate current required to electroporate a cell with an electrode of a particular size, shape, and distance from the cell. We validate the approach with electroporation of single A549 cells.