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Objective:To evaluate the proper blood collection time and calculation formula by measuring the iohexol plasma clearance as a representative of glomerular filtration rate at the same time of routine enhanced computed tomography (CT) examination.Methods:The prospective study method was applied, and 9 subjects with normal renal function, who admitted in Civil Aviation General Hospital from September 2018 to June 2019, were included. A single bolus of a standard dose (5 ml) (iodine concentration: 350 mgI/ml) was injected. The concentration of iohexol was measured from heparin plasma at fasting state of the subject and at nine different times after the injection, respectively. More than 24 hours after the injection of the standard dose, an enhanced CT-level dose (50 ml) of iohexol was injected to the subject and the concentration of iohexol was measured at similar time points as the standard dose. Using a multi-point method of a standard dose as the standard, the clearance rate was calculated by three kinds of formulas including Groth and Aasted formula, Jacobsson formula and Fleming formula with the single-point method to assess iohexol plasma clearance at 0.5 to 8.0 hours post injection of enhanced CT-level dose. The correlation consistency and accuracy of the multi-point method and the single-point method, as well as the dual-point method and the single-point method were compared, and the proper blood collection time and calculation formula of the single-point method at regular enhanced CT-level dose were evaluated. The correlation between the multi-point method and the single-point method, as well as the dual-point method and the single-point method were assessed using Pearson correlation coefficient; the consistency between the multi-point method and the single-point method, as well as the dual-point method and the single-point method were assessed by bias using mean±standard deviation ( SD) and 95% confidence interval ( CI) of mean difference and so on. We assessed the concordance of GFR using GFR±5% ( P5),±10% ( P10) and 1±30% ( P30) intervals. Results:Compared with the multi-point method, the mean deviation of iohexol plasma clearance obtained by the three single-point methods increased gradually from 5 hours after the injection of iohexol ( P<0.05). Compared with the multi-point method, only 3 h results, which was calculated by the Groth and Aasted formula, reached a P value greater than 0.05, a correlation coefficient of 0.938, a mean deviation of (-5.2±8.8) ml·min -1·1.73 m -2, and the concordances were 100% corresponding to P30,77.8% corresponding to P10, and 66.7% corresponding to P5; the 2, 3 and 4 hours results, which was calculated by the Jacobsson formula, reached P values greater than 0.05, when the blood collection time was 3 hours, the correlation coefficient was 0.938, and the mean deviation was the smallest, which was (1.5±6.2) ml·min -1·1.73 m -2, and the concordances were 100% corresponding to P30, 88.9% corresponding to P10, and 66.7% corresponding to P5; the 2 and 3 hours results, which was calculated by the Fleming formula, reached P values greater than 0.05, when the blood collection time was 2 h, the correlation coefficient was 0.956, and the mean deviation was the smallest, which was (-4.5±8.8) ml·min -1·1.73 m -2, and the concordances were 100% corresponding to P30, 77.8% corresponding to P10, and 55.6% corresponding to P5,Compared with the dual-point method, when Groth or Aasted formula was used, the mean deviation was the smallest at 3 hours, which was (-5.3±5.7) ml·min -1·1.73 m -2; when Jacobsson formula was used, the mean deviation was the smallest at 2 hours, which was (1.6±1.6) ml·min -1·1.73 m -2; when Fleming formula was used, and the mean deviation was the smallest at 2 hours, which was (-4.6±4.0) ml·min -1·1.73 m -2. Conclusion:At a regular enhanced CT-level dose, one blood collection can accurately measure the glomerular filtration rate, the proper time for blood collection can be 3 hours after iohexol injection, and the appropriate calculation formula can be Jacobsson formula.
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Since the first edition of ISO15189"Medical laboratories: requirements for quality and competence" was published in 2003, it has been rapidly and widely used in the world under the promotion of the International Laboratory Accreditation Cooperation Organization (ILAC), and has become the basic standard for the quality management, capacity-building and capacity attestation of medical laboratories. The Mutual Recognition Arrangement (MRA) of ILAC for ISO15189 is the most authoritative international permit for examination results, which is accepted by international organizations. Since the establishment of ISO15189 medical laboratory accreditation system in 2004 in China, more than 530 medical laboratories have been accredited, which plays an important role in improving the quality and competence of medical laboratories in China, and improves the influence of Chinese medical laboratories in the world. ISO 15189:2012 is currently being revised by the International Organization for Standardization/Technical Committee on Clinical Laboratory Testing and in vitro diagnostic test systems (ISO/TC212). This revision will bring significant changes and the medical laboratory shall pay attention to these changes. In order to help medical laboratories understand the new ideas in advance, this paper summarizes and analyses the draft of the new international standards, and provides references for users.
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Objective To develop an isotope dilution liquid chromatography tandem mass spectrometry (ID-LC-MS/MS) method for determining the concentration of 5-methyltertrahydrofolate (5MT) in human serum.Methods After qualitative analysis of 5MT reference,its purity was identified by two methods with different principle,i.e.,mass balance and quantitative nuclear magnetic resonance.The definite value and uncertainty of 5MT concentrations in 6 serum samples containing same level of 5MT were assessed by ultra performance liquid chromatography-triple quadrupole tandem mass spectrometer equipped with electrospray ionization in monitoring mode of multiple reactions,in which 13C5-5MT was used as the internal standard.The precision,accuracy,limit of detection (LOD) and limit of quantification (LOQ) of the method were also evaluated.Results After qualitative analysis for confirming the principal component in the sample,the purity of 5MT reference was measured as 76.65％ by mass balance and quantitative nuclear magnetic resonance method.The definite value of 5MT in the serum sample was 8.22 ng/mL,the extended uncertainty was 0.54 ng/mL,LOD was 0.05 ng/mL,LOQ was 0.50 ng/mL and the repeatability and inter-batch precision CV were within 5.0％.The accuracy of measured results was verified by using NIST SRM 1955 since all the values of 3 levels were within the range of certified value with the extended uncertainty.Conclusion A accurately quantitative determination for the concentration of 5 MT in human serum with high specificity and sensitivity was established by using ID-LC-MS/MS method.
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Obejective To evaluate the accuracies of ten commercial total 25-hydroxyvitamin D [25(OH) D] immnoassays.Methods NIST 25 (OH) D reference material SRM 972a,which consisted of four vials of frozen serum with different concentration levels of different 25 (OH) D types,and two human serumsamples provided by our lab (BIMT),which had different concentration levels of 25 (OH) D3,were analyzed by ten total 25-hydroxyvitamin D immnoassays from Biomerieux,Mindray,Maccura,Chemclin,Abbott (2),Siemens,SNIBE (2),Roche,and by isotope-dilution liquid chromatography-tandem mass spectrometry(ID-LC/MS/MS) founded by BIMT.For the measurements of SRM 972a,the biases between tested values and certified values were calculated as a evaluating indicator,meanwhile the test biases between immnoassays and ID-LC/MS/MS were used as a evaluating indicator for the measurements of BIMT 25(OH) D3 serum samples.Test bias lower than 10％ was deemed acceptible.Results The ID-LC/MS/MS exhibited low biases at (1.6％-2.8％) in the measurements of all levels of SRM 972a.8 immnoassays showed low biases at(1.5％-3.5％) in the measurements of level 1 of SRM 972a,which had a high 25(OH) D3 concentration level,but only 2 immnoassays gave low biases at (3.6％-3.7％)in the measurements of high 25 (OH)D2 concentration sample (level 3).While,5 immnoassays gave low biases at (-0.3％-9.0％) in the measurements of high 3-epi-25 (OH) D3 concentrationsample (level 4).It seems that,when SRM 972a were analyzed,only one of the ten commercial total 25 (OH)D immnoassays were in good accuracy and analytical specificity agrements with ID-LC/MS/MS.When two human serum25(OH) D3samples from BIMT were tested,most immunoassays were overall in relative good agreement with ID-LC/MS/MS at high 25 (OH) D3concentration level.Conclusion The test biases in the total 25 (OH) D measurements are differences between differentimmnoassays and ID-LC/MS/MS,and the specificities of current commercial total 25 (OH) D immnoassays should be improved,especially the performance on the equivalent recognition of 25 (OH) D2 and 25 (OH) D3.