Establishment of a reference procedure to measure urine-formed elements and evaluation of an automated urine analyzer.

A standardized reference method is needed to accurately and precisely measure urine-formed elements (UFEs; red blood cells [RBCs], white blood cells [WBCs], and squamous epithelial cells [sECs]). We compared the results from a standard method with those from an automated analyzer. Trained technicians used standardized bright-field microscopy of fresh non-centrifuged urine samples, and disposable 1 µl chambers. Fifteen experienced technicians from 5 hospitals (3 per hospital) each performed 6 manual counts of 10 different native urine samples using a manual chamber and standard methods. The sEC counts were at least 50/µL, and the coefficient of variation (CV) was less than 14%; the RBC and WBC counts were at least 200/µL and the CVs were less than 7%. The same samples were also analyzed 6 times using automated analyzers. The means, CVs, and biases were determined. The median CVs for the manual measurements were 6.4% (WBCs), 6.6% (RBCs), and 12.7% (sECs). The CVs of the automated analyzer were 4.7% (WBCs), 5.6% (RBCs), and 9.2% (sECs). Biases between the automated and manual methods were -2.9% to 5.0%(WBCs), -0.8% to 8.8% (RBCs) and -2.8% to 9.4% (sECs). The count mean values and expanded uncertainties of these counts were (224.5 ± 15.0) cells/µL, (234.2 ± 16.2) cells/µL, and (61.5 ± 7.9) cells/µL, respectively. The standardized manual method for measuring UFEs had high precision and accuracy, making it a suitable reference method. Use of this reference method to calibrate an automated analyzer improved the accuracy of automated analysis.

Application of Commutable ERM-DA474/IFCC for Harmonization of C-reactive Protein Measurement Using Five Analytical Assays.

BACKGROUND: ERM-DA474/IFCC has been used as a reference material for C-reactive protein (CRP) since 2012. However, the commutabilities and the capacity for harmonizing CRP results of the material and its dilutions have not yet been reported. In this study, we aimed to evaluate the harmonization of CRP results using commutable ERM-DA474/IFCC. METHODS: Twenty-one serum samples were collected and split into five vials. The samples were then analyzed using five popular assays (Siemens BN II, Beckman Immage 800, Roche, Diasys, and Leadman). ERM-DA474/IFCC and four dilutions of healthy human serum containing low levels of CRP were also analyzed using the five assays described above. Commutability was assessed using the Roche, Diasys, and Leadman assays. Clinical sample results from assays were recalibrated based on ERM-DA474/IFCC and its dilutions. RESULTS: There were significant variations among the five assays for CRP measurement. The slopes ranged from 0.60 to 1.60, and the BN II and Leadman assays showed significant negative and positive systemic biases, respectively. ERM-DA474/IFCC and its dilutions exhibited commutability among the three assays. After recalibration, the slope was reduced to 0.76 - 1.27. CONCLUSIONS: Harmonization was not ideal for CRP measurement. ERM-DA474/IFCC may play a role in improving harmonization for CRP measurement.

Modified HPLC-ESI-MS Method for Glycated Hemoglobin Quantification Based on the IFCC Reference Measurement Procedure and Its Application for Quantitative Analyses in Clinical Laboratories of China.

BACKGROUND: The level of glycated hemoglobin (HbA1c ) has been recognized as an important indicator of long-term glycemic control. However, the HbA1c measurement is not currently included as a diagnostic determinant in China. Current study aims to assess a candidate modified International Federation of Clinical Chemistry reference method for the forthcoming standardization of HbA1c measurements in China. METHODS: The HbA1c concentration was measured using a modified high-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) method. The modified method replaces the propylcyanide column with a C18 reversed-phase column, which has a lower cost and is more commonly used in China, and uses 0.1% (26.5 mmol/l) formic acid instead of trifluoroacetic acid. Moreover, in order to minimize matrix interference and reduce the running time, a solid-phase extraction was employed. The discrepancies between HbA1c measurements using conventional methods and the HPLC-ESI-MS method were clarified in clinical samples from healthy people and diabetic patients. Corresponding samples were distributed to 89 hospitals in Beijing for external quality assessment. RESULTS: The linearity, reliability, and accuracy of the modified HPLC-ESI-MS method with a shortened running time of 6 min were successfully validated. Out of 89 hospitals evaluated, the relative biases of HbA1c concentrations were < 8% for 74 hospitals and < 5% for 60 hospitals. Compared with other conventional methods, HbA1c concentrations determined by HPLC methods were similar to the values obtained from the current HPLC-ESI-MS method. CONCLUSION: The HPLC-ESI-MS method represents an improvement over existing methods and provides a simple, stable, and rapid HbA1c measurement with strong signal intensities and reduced ion suppression.

Point-of-care testing of HbA1C is traceable to IFCC reference method by external calibration.

BACKGROUND: POCT for HbA1C is widely used in China. However, the lack of traceability of POCT leads to poor comparability of patient results. METHODS: The first step was the evaluation of the precision of NycoCard and DCA by using two-level patient specimens. The second step was the calibration of the central laboratory instrument G8 HBA1C Variant with samples whose values had been assigned by an IFCC reference method. The third step was the assignment of values to 50 fresh whole blood patient specimens by this calibrated G8. The fourth step was to use these 50 fresh whole blood patient specimens to calibrate and to revise the POCT instruments. The fifth step was to confirm whether these 50 specimens were required through mathematical calculations. RESULTS: The low and high CVs at levels were 3.61% and 1.85% for NycoCard but 1.71% and 2.85% for DCA. The linear equation of NycoCard to calibrated G8 and that of DCA to calibrated G8 were Y=0.8530X+0.6409 and Y=0.8995X+0.3891, respectively, and the correlation coefficient for every POCT instrument was greater than 0.985. By external calibration of POCT instruments, the mean deviation detected by NycoCard was reduced from -4.0±3.4mmol/mol to 0.5±3.9mmol/mol, and that by DCA went down to 0.2±3.3mmol/mol. The minimum specimen size for the external calibration of POCT instrument was 10. CONCLUSION: POCT measurement traceability can be established by external calibration. Using an external calibration mode improves the comparability of POCT patient results.

An improved candidate reference method for serum potassium measurement by inductively coupled plasma-mass spectrometry.

BACKGROUND: In 2002, the National Institute of Standards and Technology (NIST) established a reference method for serum potassium based on inductively coupled plasma-mass spectrometry (ICP-MS). The aim of this study was to develop an inexpensive and improved candidate reference method for accurate and precise determination of serum potassium. METHODS: Serum samples were diluted with 1% HNO3 supplemented with (59)Cobalt as isotope internal standard, and potassium was measured by ICP-MS. The new method was evaluated with NIST standard reference materials (SRMs), according to the Clinical and Laboratory Standard Institute's evaluation protocols. RESULTS: At 4.300 and 4.678 mmol/l levels, the present method demonstrated analytical imprecision of 0.09% and 0.14%, and recoveries of 99.67% to 99.88%, respectively. The bias between the target values of SRMs were -0.02% to +0.28%, respectively. This method was linear between 0.0000 and 6.87 mmol/l (R(2)=1.000). The method had an uncertainty (U95%) of 0.76%. CONCLUSIONS: The proposed ICP-MS method to measure serum potassium is precise and accurate, with high sensitivity and specificity. It may be considered as a candidate reference method for the determination of serum potassium.