12/3/2023 0 Comments Labcorp sequential screening![]() Inclusivity studies were performed by amplifying 42 genomic DNA samples representing diverse types of bacteria (including mycobacteria) expected to be present in the specimen types acceptable for this assay. No cross-reactivity to these organisms was observed. Specificity was tested using a panel of 10 nucleic acid extracts from viral, fungal, and parasitic organisms. The limit of detection was less than 65 colony forming units per PCR reaction for all sources as determined by spiking Streptococcus gallolyticus and Escherichia coli into PCR-negative fresh tissue, synovial fluid, f ormalin-fixed, paraffin-embedded tissue, sonicate fluid, body fluid, and cerebrospinal fluid. ![]() Testing demonstrated 100% correlation with expected results from spiked material. Some samples were spiked with gram-negative or gram-positive bacteria due to the scarcity of clinically positive samples. Using criteria established in verification, sensitivity of the assay is 99% and specificity is 97%. All samples were tested with both Sanger and next-generation sequencing (NGS) technologies enabling resolution of poor-quality Sanger results and identifying polybacterial presence in some samples. In addition, 63 negative samples from previous Sanger sequence-based testing were used in verification. One hundred thirty positive patient specimens were available for accuracy studies and correlated with results of culture, organism-specific polymerase chain reaction (PCR), or previous broad-range bacterial PCR and sequencing. Heart valves from patients with endocarditis with positive Gram stains are, for example, especially suitable. Ideal specimens are those in which bacteria (includes mycobacteria) are visualized by microscopy. Next-generation sequencing can be useful in such cases. Sterile sources accepted for testing may have more than one bacterial species present or the presence of copy variants of the 16S rRNA gene within a single bacterial species, confounding Sanger sequencing analysis. Polymerase chain reaction amplification of a portion of the 16S ribosomal RNA (rRNA) gene followed by sequencing of the amplified product can be used to detect bacterial (including mycobacterial) nucleic acids in such situations, enabling a diagnosis. Specimen Stability Information: Frozen <14 days (preferred)/ Refrigerated <14 daysĬultures from patients with suspected bacterial infection involving normally sterile sites may fail to provide bacterial (including mycobacterial) growth for identification due to the presence of fastidious or slow-growing bacteria or as a result of antecedent antimicrobial chemotherapy. Specimen Stability Information: Frozen <14 days(preferred)/Refrigerated <14 daysĪcceptable: Lavender top (EDTA), pink top (EDTA), royal blue top (EDTA), or sterile vial containing EDTA-derived aliquotĬollection Instructions: Send specimen in original tube (preferred). Sources: Normally sterile body fluids such as cerebrospinal, vitreous humor, pleural, abdominal, peritoneal, ascites, pericardial, pelvic, prostaticĬontainer/Tube: Screw-capped, sterile container Each section (scroll) must be placed in a separate sterile container for submission. Specimen Type: Section (scrolls) of FFPE tissue blockĬontainer/Tube: Sterile container for each individual cut section (scroll)Ĭollection Instructions: Perform microtomy and prepare five separate 10-micron sections. Specimen Stability Information: Ambient (preferred)/RefrigeratedĪcceptable: Paraffin-embedded tissue block: Sources: Normally sterile or deep tissues such as bone, lymph node, joint, heart valve, brain, viscera, organ, lung, prostateĬollection Instructions: Submit a formalin-fixed, paraffin-embedded tissue block to be cut and returned. Specimen Type: Formalin-fixed, paraffin-embedded (FFPE) tissue block Preferred: Paraffin-embedded tissue block: Specimen Stability Information: Frozen <14 days (preferred)/Refrigerated <14 days Submit tissue only, do not add fluid to tissue. Specimen Volume: Entire collection or 5 mm(3)-approximately the size of a pencil eraserĢ. Sources: Normally sterile tissue such as bone, lymph node, joint, heart valve, brain, viscera, organ, lung, prostate ![]() ![]() Submit only 1 of the following specimens: Fresh tissue is preferred over formalin-fixed, paraffin-embedded tissue.
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