Comparison and bias estimation of isotope dilution mass spectrometry and HPLC for cholesterol:methodological comparison of two internationally accepted reference methods listed in JCTLM / 中华检验医学杂志

Objective To evaluate the consistency and comparability of two kinds of cholesterol reference methods listed in the Joint Committee for Traceability in Laboratory Medicine(JCTLM).Methods 52 fresh frozen sera with cholesterol concentrations among 3 -10 mmol/L were tested by isotope dilution liquid chromatography tandem mass spectrometry (ID-LC/MS/MS)and high performance liquid chromatography(HPLC).The precision and accuracy of the two methods were calculated,and then a series of analysis were conducted including plotting scatter plots and deviation graphs,testing outliers,selecting the best fitting regression models and calculating the regression equations and parameters,and so on.The results of the two methods were statistically analyzed to estimate the expected deviation at the level of medical decision of cholesterol and the 95% confidence range.Results For HPLC method,the CV of instrument measurement was 0.22%(0 -0.49%),the total CV of samples measurement was 0.36%(0.02% -0.83%),and the average bias of the reference materials was 0.37%(-1.31%-0.14%).For ID-LC/MS/MS method,the CV of instrument measurement was 0.50%(0 -1.51%),the total CV of samples measurement was 0.55%(0.03%-1.17%),and the average bias of the reference materials was 0.24%(-0.53%-0.14%).No outliers were found from the scatter plots and the statistical analysis and the linear regression were fitted to analyze the results of the two methods.The linear regression parameters of two methods for 52 fresh frozen human sera were as follows:the slope was 0.989 5,the standard error of slope was 0.003 4,the intercept was 0.063 4 mmol/L,the standard error of intercept was 0.019 9 mmol/L,the standard error of Y-estimate was 0.034 8 mmol/L,and the correlation coefficient was 0.999 7.Compared with the ID-LC/MS/MS method,the absolute deviation of fresh sera by HPLC method was 0.000 mmol/L (-0.083-0.076 mmol/L),with a relative deviation of 0.07%(-1.22-1.24%).T-test results showed no statistically significant difference between the two methods.The expected deviations at the cholesterol medicine decision level were within the range 95% confidence range,and the expected deviations were far less than the allowable error.Conclusions The HPLC method of cholesterol has good consistency and comparability with ID/MS method using the primary measurement principle.Because of more advantages of HPLC method such as less cost,more simple,requirement,and better precision,HPLC method is expected to play an important role in the process of standardization and traceability of serum cholesterol.

Detection bias evaluation of ten commercial total 25-hydroxyvitamin D immunoassays / 中华检验医学杂志

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.

The measurement of steroid hormone by isotope dilution mass spectrometry / 中华检验医学杂志

Isotope dilution mass spectrometry is a reliable principle for small molecule analyte measurements.It is a precise,accurate method with very high specificity,which is very suitable for lowconcentration steroid hormones tests.The published reference methods are all based on this principle so far.In this paper,the applications of isotope dilution mass spectrometry in the determination of steroid hormones were reviewed.

Early Vascular Access Blood Flow as a Predictor of Long-term Vascular Access Patency in Incident Hemodialysis Patients

The long-term clinical benefits of vascular access blood flow (VABF) measurements in hemodialysis (HD) patients have been controversial. We evaluated whether early VABF may predict long-term vascular access (VA) patency in incident HD patients. We enrolled 57 patients, of whom 27 were starting HD with arteriovenous fistulas (AVFs) and 30 with arteriovenous grafts (AVGs). The patients' VABF was measured monthly with the ultrasound dilution technique over the course of the first six months after the VA operation. During the 20.4-month observational period, a total of 40 VA events in 23 patients were documented. The new VA events included 13 cases of stenosis and 10 thrombotic events. The lowest quartile of average early VABF was related to the new VA events. After adjusting for covariates such as gender, age, hypertension, diabetes, VA type, hemoglobin levels, body mass index, parathyroid hormone, and calcium-phosphorus product levels, the hazard ratio of VABF (defined as <853 mL/min in AVF or <830 mL/min in AVG) to incident VA was 3.077 (95% confidence interval, 1.127-8.395; P=0.028). There were no significant relationships between early VABF parameters and VA thrombosis. It is concluded that early VABF may predict long-term VA patency, particularly VA stenosis.