Effective and Practical Complete Blood Count Delta Check Method and Criteria for the Quality Control of Automated Hematology Analyzers.

Background: Delta checks increase patient safety by identifying automated hematology analyzer errors. International standards and guidelines for the complete blood count (CBC) delta check method have not been established. We established an effective, practical CBC delta check method and criteria. Methods: We assessed five delta check methods for nine CBC items (Hb, mean corpuscular volume, platelet count, white blood cell [WBC] count, and five-part WBC differential counts) using 219,804 blood samples from outpatients and inpatients collected over nine months. We adopted the best method and criteria and evaluated them using 42,652 CBC samples collected over two weeks with a new workflow algorithm for identifying test errors and corrections for Hb and platelet count. Results: The median delta check time interval was 1 and 21 days for inpatients and outpatients (range, 1-20 and 1-222 days), respectively. We used delta values at 99.5% as delta check criteria; the criteria varied among the five methods and between outpatients and inpatients. The delta percent change (DPC)/reference range (RR) rate performed best as the delta check for CBC items. Using the new DPC/RR rate method, 1.7% of total test results exceeded the delta check criteria; the retesting and resampling rates were 0.5% and 0.001%, respectively. Conclusions: We developed an effective, practical delta check method, including RRs and delta check time intervals, and delta check criteria for nine CBC items. The criteria differ between outpatients and inpatients. Using the new workflow algorithm, we can identify the causes of criterion exceedance and report correct test results.

[Microbiological and epidemiological characteristics of vancomycin-dependent enterococci].

BACKGROUND: Vancomycin-dependent enterococci (VDE) are clinically equivalent to vancomycin-resistant enterococci (VRE), but more difficult to detect. This study was purposed to characterize VDE microbiologically and epidemiologically. METHODS: The patients from whom VDE were detected from April 2007 to March 2008 were investigated. For available isolates, minimal inhibitory concentrations (MICs) of and the levels of dependence on vancomycin and teicoplanin were measured by E test (AB Biodisk, Sweden), and a test for reversion of VDE to non-dependent VRE (NDVRE) and pulsed field gel electrophoresis (PFGE) were performed. Patients' demographic and clinical findings were reviewed via electronic medical records. RESULTS: VDE were recovered from 6 (2.2%) of 272 patients carrying VRE during this study period. All patients were already colonized or infected by VRE and treated with vancomycin for 13 to 107 days. VDE were isolated from pleural fluid (one), urine (four), and stool (one). All isolates carried vanA with vancomycin MICs of >256 microg/mL, but two of them had intermediate susceptibilities to teicoplanin. Because 4 VDE isolates were reverted to NDVRE with single passage, vancomycin dependence was measurable for only two isolates as equal and above 0.064 and 0.5 microg/mL respectively, and was reverted after 5 and 7 passages, respectively. Six VDE isolates showed no related clones in PFGE analysis, and 3 of 4 available pairs of initial VRE isolates and subsequent VDE isolates were identical clones. CONCLUSIONS: VDE were not rare and seemed to emerge independently from VRE with a prolonged use of vancomycin. Vancomycin-dependence was reverted within several passages.

Comparative evaluation of two automated systems for nucleic acid extraction of BK virus: NucliSens easyMAG versus BioRobot MDx.

The objective of this study was to compare the performance of two automated nucleic acid extraction systems. Specifically, the NucliSens easyMAG system (bioMerieux, Marcy l'Etoile, France), which incorporates magnetic bead technology, was compared with the BioRobot MDx system (Qiagen GmbH, Hilden, Germany), which uses a silica membrane-based method of nucleic acid extraction. Nucleic acids from the BK virus (BKV DNA) were extracted from 98 plasma and 57 urine specimens using the Real-Q BKV quantitation kit (Biosewoom, Seoul, Korea). Failed PCR was defined as negative BKV DNA results having more than 36 threshold cycles of the internal control by the manufacturer's instruction. The PCR failure rate of nucleic acids isolated from plasma samples using the MDx system was similar to that of plasma samples processed using the easyMAG system (2.0% and 3.1%, respectively). The PCR failure rate of nucleic acids isolated from urine samples using the MDx system was higher than that of urine samples processed using the easyMAG system (33.3% and 12.5%, respectively). These data suggest that the PCR inhibitors present in urine specimens are removed more efficiently by the easyMAG system. Among amplified specimens, the discordant results obtained from the two systems revealed that the BKV DNA load ranged from 2.3 log10 copies/mL to 4.6 log10 copies/mL. Of the 25 urine specimens that yielded BKV DNA by both extraction systems, 15 specimens (60.0%) yielded higher BKV DNA loads by the easyMAG system, indicating that the easyMAG system extracted nucleic acid more efficiently than did the MDx system. In conclusion, the easyMAG method outperformed the MDx method when used to extract BKV DNA from urine samples. Magnetic bead-based extraction methods such as the easyMAG system are therefore preferable for the quantitation of viral DNA in urine.