BACKGROUND: Measurement uncertainty characterizes the dispersion of the quantity values attributed to a measurand. Although this concept was introduced to medical laboratories some years ago, not all medical researchers are familiar with it. Therefore, the evaluation and expression of measurement uncertainty must be highlighted using a practical example. METHODS: In accordance with the procedure for evaluating and expressing uncertainty, provided by the Joint Committee for Guides in Metrology (JCGM), we used plasma glucose (Glu) as an example and defined it as the measurand. We then analyzed the main sources of uncertainty, evaluated each component of uncertainty, and calculated the combined uncertainty and expanded uncertainty with 2 budgets for single measurements and continuous monitoring, respectively. RESULTS: During the measurement of Glu, the main sources of uncertainty included imprecision, within-subject biological variance (BVw), calibrator uncertainty, and systematic bias. We evaluated the uncertainty of each component to be 1.26%, 1.91%, 5.70%, 0.42%, and -2.87% for within-run imprecision, between-day imprecision, BVw, calibrator uncertainty, and systematic bias, respectively. For a single specimen, the expanded uncertainty was 7.38% or 6.1+/-0.45 mmol/L (kappa=2); in continuous monitoring of Glu, the expanded uncertainty was 13.58% or 6.1+/-0.83 mmol/L (kappa=2). CONCLUSIONS: We have demonstrated the overall procedure for evaluating and reporting uncertainty with 2 different budgets. The uncertainty is not only related to the medical laboratory in which the measurement is undertaken, but is also associated with the calibrator uncertainty and the biological variation of the subject. Therefore, it is helpful in explaining the accuracy of test results.
Blood Chemical Analysis/methods/standards ; Clinical Chemistry Tests/*methods/standards ; Glucose/*analysis/standards ; Humans ; Models, Statistical ; Quality Control ; *Uncertainty

BACKGROUND: Measurement uncertainty characterizes the dispersion of the quantity values attributed to a measurand. Although this concept was introduced to medical laboratories some years ago, not all medical researchers are familiar with it. Therefore, the evaluation and expression of measurement uncertainty must be highlighted using a practical example. METHODS: In accordance with the procedure for evaluating and expressing uncertainty, provided by the Joint Committee for Guides in Metrology (JCGM), we used plasma glucose (Glu) as an example and defined it as the measurand. We then analyzed the main sources of uncertainty, evaluated each component of uncertainty, and calculated the combined uncertainty and expanded uncertainty with 2 budgets for single measurements and continuous monitoring, respectively. RESULTS: During the measurement of Glu, the main sources of uncertainty included imprecision, within-subject biological variance (BVw), calibrator uncertainty, and systematic bias. We evaluated the uncertainty of each component to be 1.26%, 1.91%, 5.70%, 0.42%, and -2.87% for within-run imprecision, between-day imprecision, BVw, calibrator uncertainty, and systematic bias, respectively. For a single specimen, the expanded uncertainty was 7.38% or 6.1+/-0.45 mmol/L (kappa=2); in continuous monitoring of Glu, the expanded uncertainty was 13.58% or 6.1+/-0.83 mmol/L (kappa=2). CONCLUSIONS: We have demonstrated the overall procedure for evaluating and reporting uncertainty with 2 different budgets. The uncertainty is not only related to the medical laboratory in which the measurement is undertaken, but is also associated with the calibrator uncertainty and the biological variation of the subject. Therefore, it is helpful in explaining the accuracy of test results.
Blood Chemical Analysis/methods/standards ; Clinical Chemistry Tests/*methods/standards ; Glucose/*analysis/standards ; Humans ; Models, Statistical ; Quality Control ; *Uncertainty

This article elucidates the understanding of National Standard GB/T19634-2005 "In Vitro Diagnostic Test Systems-General Technical Requirements for Blood-Glucose Monitoring Systems for Self-Testing" from the perspective of registration tests of blood glucose analyzers, and summarizes some of the common problems existing in sending the blood glucose analyzers for inspection in registration tests according to the relevant regulations.
Blood Glucose ; analysis ; Blood Glucose Self-Monitoring ; instrumentation ; standards ; Health Personnel

BACKGROUND: Commutable reference materials (RMs) are suitable for end-users for evaluating the metrological traceability of values obtained using routine measurement systems. We assessed the performance of 6 routine measurement systems with validated secondary RMs. METHODS: We tested the homogeneity, stability, and commutability of 5 minimally processed human serum pools according to the standard guidelines. The serum pools were assigned values as per the reference procedure of the United States Centers for Disease Control and were used to evaluate the trueness of results from 6 commercial measurement systems based on enzymatic methods: 3 glucose oxidase (GOD) and 3 hexokinase (HK) methods. RESULTS: The prepared RMs were validated to be sufficiently homogenous, stable, and commutable with the patient samples. Method bias varied for different systems: GOD01, -0.17 to 2.88%; GOD02, 1.66 to 4.58%; GOD03, -0.17 to 3.14%; HK01, -3.48 to -0.85%; HK02, -3.83 to -0.11%, and HK03, -1.82 to -0.27%. CONCLUSIONS: We observed that the prepared serum glucose RMs were qualified for trueness assessment. Most of the measurement systems met the minimal quality specifications.
Blood Chemical Analysis/instrumentation/*standards ; Blood Glucose/*analysis ; Glucose Oxidase/metabolism ; Hexokinase/metabolism ; Humans ; Reagent Kits, Diagnostic ; Reference Standards ; Regression Analysis

Blood Glucose ; analysis ; Capillaries ; metabolism ; Humans ; Hypoglycemia ; diagnosis ; Infant, Newborn ; Neonatal Screening ; methods ; Reference Standards

Through the present delta value check used in quality control programs is a powerful tool for detecting random errors in clinical chemistry analysis, it has some problems, such as missed true errors and delays in reporting time, because it also has the potential of showing erroneous positive results. Recently, new calculation methods for delta check with delta difference, delta percent change, rate difference, and rate percent change have been suggested by Lacher and Connelly (Clin Chem 34:1966-1970, 1988). Based on this new delta check method, we made the new criteria of which calculation method is applied to the clinical chemistry tests, i.e., the differential application of rate and delta check, and selectively applied the new method to 17 chemistry tests in order to solve the above problems. The applied criteria were the time dependence of the test item and the coefficient of variation of the absolute delta difference. Calcium, inorganic phosphorus, total protein, albumin, sodium, potassium, and chloride were classified as delta difference calculation method group; glucose and cholesterol as delta percent change group; creatinine, total and direct bilirubin as rate difference group; and urea nitrogen, uric acid, ALP, ALT, and AST as rate percent change group. With the previous criteria by Whitehurst et al. (Clin Chem 221:87-92) for 5045 specimens, the check-out rate was 47.8% (2,411 out of 5,045), and the positive predictive value was 0.41% (10 out of 2,411). For the new criteria, the check-out rate was 12.7% (621 out of 5,045), and the positive predictive value was 1.8% (nine out of 621).(ABSTRACT TRUNCATED AT 250 WORDS)
Albumins/analysis ; Bilirubin/analysis ; Calcium/analysis ; Chemistry, Clinical/methods/*standards ; Clinical Laboratory Information Systems/*standards ; Creatine/analysis ; Glucose/analysis ; Phosphorus/analysis ; Quality Control ; Reference Values ; *Sensitivity and Specificity ; Specimen Handling ; Urea/analysis ; Work Simplification

BACKGROUND/AIMS: The application of glycated hemoglobin (HbA1c) for the diagnosis of diabetes is currently under extensive discussion. In this study, we explored the validity of using HbA1c as a screening and diagnostic test in Chinese subjects recruited in Nanjing, China. METHODS: In total, 497 subjects (361 men and 136 women) with fasting plasma glucose (PG) > or = 5.6 mmol/L were recruited to undergo the oral glucose tolerance test (OGTT) and HbA1c test. Plasma lipid, uric acid, and blood pressure were also measured. RESULTS: Using a receiver operating characteristic curve, the optimal cutoff point of HbA1c related to diabetes diagnosed by the OGTT was 6.3%, with a sensitivity and specificity of 79.6% and 82.2%, respectively, and the area under the curve was 0.87 (95% confidence interval, 0.83 to 0.92). A HbA1c level of 6.5% had a sensitivity and specificity of 62.7% and 93.5%, respectively. When comparing the HbA1c > or = 6.5% or OGTT methods for diagnosing diabetes, the former group had significantly higher HbA1c levels and lower levels of fasting and 2-hour PG than the latter group. No significant difference was observed in the other metabolism indexes between the two groups. CONCLUSIONS: Our results suggest that HbA1c > or = 6.5% has reasonably good specificity for diagnosing diabetes in Chinese subjects, which is in concordance with the American Diabetes Association recommendations.
Aged ; Analysis of Variance ; *Asian Continental Ancestry Group ; Biological Markers/blood ; Blood Glucose/analysis ; China/epidemiology ; *Chromatography, High Pressure Liquid/standards ; *Chromatography, Ion Exchange/standards ; Diabetes Mellitus, Type 2/blood/*diagnosis/ethnology ; Fasting/blood ; Female ; Glucose Tolerance Test/standards ; Hemoglobin A, Glycosylated/*analysis ; Humans ; Male ; Mass Screening/*methods/standards ; Middle Aged ; Predictive Value of Tests ; ROC Curve ; Reference Standards ; Reproducibility of Results ; Sensitivity and Specificity

BACKGROUND: We have evaluated the analytical performance of SureStep Flexx (Johnson and Johnson, USA) which can report the plasma equivalent glucose test results and be connected to the hospital information networks, following ISO15197 analytic procedure for glucometer for the first time. METHODS: Adopting the guidelines of ISO15197, we measured the precision of ten glucometers from their repeatability and intermediate precision, and determined the accuracies of the glucometer, comparing to those of GEM Premier 4000 (Instrumentation Laboratory, USA). In addition, the guidelines of CLSI EP9-A2 and EP6-A were applied to correlate between data of glucometer and those of laboratory reference method by TBA-200FR (Toshiba Medical Systems, Japan) and to examine its linearity of glucose concentrations measured by SureStep Flexx. We used the clinical specimens and commercial control materials. RESULTS: Repeatabilities and intermediate precisions of those glucometers were 4.0-7.3%, and 4.3-6.2%, respectively. When glucose levels are under 75 mg/dL, the difference between results of those meters and the reference values were within +/-6 mg/dL. However when glucose levels are over 75 mg/dL, those differences were within +/-12.7%. These results were acceptable for the ISO15197 criteria in all glucose concentrations. The glucose concentrations showed the clinically relevant linearity in the range from 36 mg/dL to 491 mg/dL. Moreover, Error Grid Analysis showed that all glucose results were in "zone A", which means that these values were clinically accurate. CONCLUSIONS: This study showed that SureStep Flexx can provide reliable results for patients and clinicians to manage the diabetes mellitus, satisfying the ISO15197 criteria.
Blood Glucose/*analysis ; Blood Glucose Self-Monitoring/*instrumentation/methods/*standards ; Diabetes Mellitus/blood/diagnosis ; Humans ; Quality Control ; Reference Values ; Reproducibility of Results

OBJECTIVETo explore the characteristics of peritoneal transport in children undergoing chronic peritoneal dialysis (PD).

METHODSPeritoneal equilibration test (PET) was carried out 10 times in 6 children (aged from 2 to 14 years) who were maintained by continuous ambulatory peritoneal dialysis (CAPD), and the peritoneal solution transport rate was evaluated by the standards of Twardowski's and Pediatric Peritoneal Dialysis Study Consortium (PPDSC)'s criteria.

RESULTSIn this study, the initial PET was performed at (38.7 +/- 15.6) days following initiation of PD, the 4-hours of peritoneal creatinine clearance (4 h-D/P) and glucose absorption (4 h-D/D(0)) was (0.85 +/- 0.24) and (0.34 +/- 0.19), respectively. According to the standards of Twardowski's and PPDSC criteria, the peritoneal transport categories were divided into high transport (H) (6/10), high average transport (HA) (1/10), low average (LA) (3/10) for peritoneal solution transport, and H (3/10), HA (4/10), LA (1/10), low transport (2/10) for glucose absorption. No low transport type of solution was used in the patients. The coincidence rate of peritoneal creatinine and glucose transport types were 100% and 90% between the Twardowski's and PPDSC criteria, respectively. The different changes of peritoneal transport type were found in two patients with continuous PET. The value of 4 h-D/P increased after peritonitis episodes.

CONCLUSIONThe results showed that the PET in 70% of CAPD children fell into high and high average transport categories elevated by PPDSC's and adult standards, no-sinusoid distribution. The peritoneal solute clearance was adequate in the children, but net water ultrafiltration was lower. Standard pediatric PET and its criteria are consistent with the adult criteria. The capability of peritoneal solute transport increased after peritonitis episodes.

Adolescent ; Child ; Child, Preschool ; Creatinine ; analysis ; Female ; Glucose ; analysis ; Humans ; Male ; Peritoneal Dialysis, Continuous Ambulatory ; Peritoneum ; metabolism ; Peritonitis ; physiopathology ; Reference Standards

BACKGROUND: This study aimed to analyze the influence of the interruption of agitation and removal of leukocytes on platelet concentrates (PCs), and determine the maximum amount of time the agitation could be interrupted without impairing PCs' effectiveness during the storage period. METHODS: Four ABO-identical random donor platelets agitated for 24 hr were pooled, and divided into 4 units, and 2 units of them were leukoreduced. Then 52 pooled units were categorized into 4 groups, non-leukoreduced continuous agitation (Non-LRCA), non-leukoreduced interrupted agitation (Non-LRIA), leukoreduced continuous agitation (LRCA), and leukoreduced interrupted agitation (LRIA), and preserved for 6 days (total 7 days). Mean platelet volume (MPV), pH, HCO3-, pO2, pCO2, CD62P, CD61, glucose, lactate, ammonia and free fatty acid were measured during the period. RESULTS: Starting from the Day 4, the pH and HCO3- of Non-LRIA group begun to decrease while the amount of lactate production, glucose consumption, and MPV increased compared to the Non- LRCA group (P<0.01). An increase in pO2 level was observed in the interrupted agitation groups as the storage period prolonged (P<0.01). The pH levels of all the units in the agitation groups remained higher than 6.4 up to Day 7, while those of the non-leukoreduction group did so only up to Day 2, but those of leukoreduction in the interrupted agitation groups did so up to Day 4. CONCLUSIONS: The interruption of agitation reduced the platelet's capacity to utilize oxygen, increasing lactate amount and reducing pH level. However, the in vitro parameters of the Non-LRIA and Non-LRCA groups on Day 2 were similar to each other and the pH level remained at 6.4 or higher, making one day of agitation interruption possible after 24 hr of agitation. With leukocytes removed, the effective agitation interruption period may become longer.
*Blood Component Removal ; Blood Platelets/*cytology ; Blood Preservation/*standards ; Cell Separation ; Glucose/analysis ; Humans ; Hydrogen-Ion Concentration ; Lactic Acid/blood ; Oximetry ; P-Selectin/blood ; Time Factors ; Vibration