Genome-wide screening of genetic alterations between normal and cancer cells, as well as among subgroups of tumors, is important for establishing molecular mechanism and classification of cancer. Gene silencing through loss of heterozygosity is widely observed in cancer cells and detectable by analyzing allelic loss of single nucleotide polymorphism and/or short tandem repeat markers. To use minute quantities of DNA that are available through laser capture microdissection (LCM) of cancer cells, a whole genome amplification method that maintains locus and allele balance is essential. We have successfully used a ø29 polymerase-based isothermal whole genome amplification method to amplify LCM DNA using a proteinase K lysis procedure coupled with a pooling strategy. Through single nucleotide polymorphism and short tandem repeat genotype analysis we demonstrate that using pooled DNA from two or three separate amplification reactions significantly reduces any allele bias introduced during amplification. This strategy is especially effective when using small quantities of source DNA. Although a convenient alkaline lysis DNA extraction procedure provided satisfactory results from using 1500 to 3000 LCM cells, proteinase K digestion was superior for lower cell numbers. Accurate genotyping is achieved with as few as 100 cells when both proteinase K extraction and pooling are applied.
The COVID-19 pandemic caused by the new SARS-CoV-2 coronavirus has imposed severe challenges on laboratories in their effort to achieve sufficient diagnostic testing capability for identifying infected individuals. In this study we report the analytical and clinical performance characteristics of a new, high-throughput, fully automated nucleic acid amplification test system for the detection of SARS-CoV-2. The assay utilizes target capture, transcription mediated amplification, and acridinium ester-labeled probe chemistry on the automated Panther System to directly amplify and detect two separate target sequences in the ORF1ab region of the SARS-CoV-2 RNA genome. The probit 95% limit of detection of the assay was determined to be 0.004 TCID50/ml using inactivated virus, and 25 c/ml using synthetic in vitro transcript RNA targets. Analytical sensitivity (100% detection) was confirmed to be 83 – 194 c/ml using three commercially available SARS-CoV-2 nucleic acid controls. No cross reactivity or interference was observed with testing six related human coronaviruses, as well as 24 other viral, fungal, and bacterial pathogens, at high titer. Clinical nasopharyngeal swab specimen testing (N=140) showed 100%, 98.7%, and 99.3% positive, negative, and overall agreement, respectively, with a validated reverse transcription PCR NAAT for SARS-CoV-2 RNA. These results provide validation evidence for a sensitive and specific method for pandemic-scale automated molecular diagnostic testing for SARS-CoV-2.
The good specificity, sensitivity, precision, subtype performance and clinical agreement with other assays demonstrated by Aptima combined with the complete automation provided by the Panther platform makes Aptima a good candidate for both VL monitoring and diagnosis of HIV-1.
BackgroundQuantitation of HIV-RNA is critically important for diagnosis, prognosis, treatment, monitoring and assessment of infectivity in HIV-1 infection. The objective of this study was to assess performance characteristics of the Aptima HIV-1 Quant Dx assay (Aptima), a new transcription mediated amplification (TMA), fully integrated and automated assay from Hologic Inc., San Diego, CA, USA.The analytical sensitivity, analytical specificity, precision and detection of HIV-1 subtypes were tested based on commercially available international standards or panels. A selected group of 244 anti-HIV-1 (+) plasma samples was used for comparison with Roche COBAS Ampliprep/COBAS TaqMan HIV- 1 test v2.0 (Roche CAP/CTM), (Roche Molecular Systems, Pleasanton, CA).ResultsThe 50 and 95 % limit of detection were estimated at 4.9 (95 % CI 3.9–5.7) and 17.6 (15.2–21.2) IU/mL respectively. The specificity was found 99.83 (99.06–99.97) %. The standard deviations and coefficient of variations for panels with 50 and 100 copies/mL (1.7 and 2 log copies/mL) were 0.14 log copies/mL (8.67 %CV) and 0.18 log copies/mL (9.91 %CV) respectively. The detection rate for Aptima and Roche assays was 220/244 (90.2 %) and 217/244 (88.9 %) respectively.ConclusionThe Aptima assay is a sensitive, specific, precise and accurate test for measuring HIV-1 viral loads and for the detection of HIV-1 infections.
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