Multicenter evaluation of analytical performances of platelet counts and platelet parameters: Carryover, precision, and stability.

INTRODUCTION: The correctness of the results of automated platelet analysis is still highly debated. The aim of this multicenter study, conducted according to international guidelines, was to verify the analytical performance of nine different types of hematology analyzers (HAs) in the automated platelet analysis. METHODS: Four hundred eighty-six peripheral blood samples (PB), collected in K3 EDTA tubes, were analyzed by ABX Pentra, ADVIA2120i, BC-6800, BC-6800 Plus, Cell-DYN Sapphire, DxH800, XE-2100, XE-5000, XN-20 with PLT-F App. Within-run imprecision and between-run imprecision were carried out using PB and material control, respectively. The carryover, low limit of quantification (LoQ), and the PB stability were evaluated. RESULTS: The carryover was absent for all HAs. The LoQ of PLT ranged between 2.0 (Cell-Dyn Sapphire) and 25.0 × 109 /L (ADVIA 2120i), while immature platelet fraction (IPF) ranged between 1.0 (XN-20) and 12.0 × 109 /L (XE-5000). The imprecision (%CV) increases as the platelet count decreases. No HAs showed desirable CVAPS for PLT counts less than 50.0 × 109 /L, with the exception of Cell-DYN Sapphire (CV 3.0% with PLT-O mean value of 26.7 × 109 /L), XN-20 (CV 2.4% with PLT-F mean value of 21.5 × 109 /L), and BC-6800 Plus (CV 1.9% with PLT-O mean value of 26.5 × 109 /L). The sample stability ranged between under two hours for MPV by ADVIA2120i and 8 hours for other PLT parameters and HAs. CONCLUSION: The findings of this study may provide useful information regarding carryover, precision, and stability of platelet counts and parameters, especially in thrombocytopenic samples. Moreover, the stability of sample for platelet analysis is conditioned by the HA and by temperature and storage time.

Evaluation of the MicroSeq 500 16S rDNA-based gene sequencing for the diagnosis of culture-negative bacterial meningitis.

Gene amplification using 16S rDNA primers has been proposed as a strategy for the diagnosis of bacterial meningitis. The aim of this study was to evaluate the performance of the MicroSeq 500 16S ribosomal DNA test (Applied Biosystems) from patients with suspected bacterial meningitis and CSF negative-culture in comparison to traditional methods. Twelve purulent culture-negative CSF samples were collected between January 2005 and January 2007. For DNA extraction, 500 microl of CSF samples were treated using the QIAamp mini kit (QIAGEN). The extracted DNA was examined amplifying 500 bp at the 5' end of 16S rRNA gene using MicroSeq500 16S rDNA Bacterial Identification PCR kit and the sequencing reactions were performed with the MicroSeq500 16S rDNA Bacterial Identification Sequencing kit (Applied Biosystems). The sequences were compared with those available in GenBank. For the culture-negative CSF samples the MicroSeq 500 16S rDNA yielded a positive result in 9 cases (75.0%): three samples were identified as Streptococcus. pneumoniae, three as Neisseria meningitidis, and the remaining 3 as Haemophilus influenzae, Abiotrophia defectiva and Porphyromonas gingivalis. The MicroSeq 500 16S ribosomal DNA test may improve the microbiological diagnosis of bacterial meningitis, especially when spinal fluid samples are obtained after the administration of antimicrobial therapy.