Trueness assessment for serum glucose measurement using commercial systems through the preparation of commutable reference materials

Impact of preconception weight loss on fasting glucose and pregnancy outcomes in women with obesity: A randomized trial

OBJECTIVE

This study examined the effectiveness of a nonsurgical, preconception weight loss intervention on pregnancy outcomes in women with obesity.

METHODS

This was a two-arm, parallel-group randomized controlled trial. A total of 164 women with BMI 30 to 55 kg/m² who were aged 18 to 38 years and planning pregnancy were randomized to a 12-week standard dietary intervention (SDI; n = 79) or a modified very low-energy diet (VLED; n = 85). Participants were observed for ≤48 weeks while trying for pregnancy and then during pregnancy. The primary outcome was maternal fasting plasma glucose at 26 to 28 weeks' gestation. Exploratory outcomes were individual and composite obesity-related adverse pregnancy outcomes.

RESULTS

Weight loss was greater in the VLED group (SDI 3.2 [0.6] kg vs. VLED 13.0 [0.5] kg, p < 0.01). In completers who had a singleton live birth (SDI 22/79 vs. VLED 35/85, p = 0.10), there was no difference in fasting glucose at 26 to 28 weeks' gestation (SDI 4.8[0.2] mmol/L vs. VLED 4.6 [0.1] mmol/L, p = 0.42). However, the composite of adverse pregnancy outcomes was significantly lower in the VLED group (p < 0.001).

CONCLUSIONS

Substantial prepregnancy weight loss in women with obesity does not alter fasting glucose at 26 to 28 weeks' gestation but does reduce a composite of adverse pregnancy outcomes. A better understanding of metabolic changes in pregnancy after preconception weight loss may assist in improving maternal and neonatal health outcomes.

Impact of blood cell counts and volumes on glucose concentration in uncentrifuged serum and lithium-heparin blood tubes

BACKGROUND

Although it is known that glucose concentration exhibits a time-dependent decay in uncentrifuged serum and lithium-heparin blood tubes, no evidence exists on how this variation may depend on blood cell counts (CBC) and volumes.

METHODS

Venous blood was drawn from 30 non fasting healthy volunteers into three serum and three lithium-heparin tubes. One serum and lithium-heparin tubes were centrifuged within 15 min after collection and glucose was measured with a hexokinase assay. The second and third serum and lithium-heparin tubes were maintained at room temperature for 1 and 2 h after the first tubes were centrifuged. These other tubes were then centrifuged and glucose was measured. CBC was performed in the first lithium-heparin tube, before centrifugation.

RESULTS

The mean decrease of glucose was higher in lithium-heparin plasma than in serum (0.33 vs. 0.24 mmol/L/h; p<0.001). Glucose concentration decreased by 7% and 5% per hour in lithium-heparin plasma and serum, respectively. In univariate analysis, the absolute decrease of glucose concentration was associated with sex (higher in men than in women), red blood cell (RBC) count, hematocrit, white blood cell (WBC) count, neutrophils and monocytes in both lithium-heparin plasma and serum. In multivariate analysis, the decrease of glucose concentration remained independently associated with RBC, WBC, neutrophils and monocytes in both sample matrices. No significant association was found with platelet number and erythrocyte or platelet volume.

CONCLUSIONS

Glucose concentration decrease in uncentrifuged lithium-heparin and serum tubes depends on the baseline number of RBC, WBC, neutrophils and monocytes within the tubes.

Health consequences for mother and baby of substantial pre-conception weight loss in obese women: study protocol for a randomized controlled trial

BACKGROUND

Current guidelines for the management of obesity in women planning pregnancy suggest lifestyle modification before conception. However, there is little evidence that lifestyle modification alters pregnancy outcomes. Bariatric surgery results in significant weight loss. This appears to reduce the risk of adverse pregnancy outcomes for the mother but may increase the risk of adverse outcomes for the infant. In order to reduce the risks of obesity-related adverse pregnancy outcomes for both mother and offspring, alternative approaches to the management of obesity in women planning pregnancy are needed.

METHODS/DESIGN

This study, a two-arm, parallel group, randomized control trial, will be conducted at the Metabolic Disorders Centre, University of Melbourne. This trial will recruit 164 women aged 18-38 years with a body mass index of 30-55 kg/m² who plan to conceive in the next 6-12 months. Women will be randomized to one of two 12-week interventions (Group A and Group B). Group A will aim for modest weight loss (MWL; ≤ 3% body weight) using a hypocaloric diet. Group B will aim for substantial weight loss (SWL; 10-15% body weight) using a modified very low energy diet (VLED) program. All participants will be asked to comply with National Health and Medical Research Council (NHMRC) guidelines for exercise and will be provided with standard pre-pregnancy advice according to Royal Australian and New Zealand College of Obstetrics and Gynaecology guidelines. All participants will then be observed for the subsequent 12 months. If pregnancy occurs within the 12-month follow-up period, data on weight and metabolic status of the mother, and pregnancy outcomes of mother and offspring will be recorded. The primary outcome is maternal fasting plasma glucose at 26-28 weeks' gestation, given that this is known to correlate with pregnancy outcomes. Time to conception, live birth rate, gestational weight gain, and a composite of adverse pregnancy outcomes for mother and baby will comprise the secondary outcomes.

DISCUSSION

There is increasing emphasis on obese women losing weight before conception. To date, no randomized controlled trial has demonstrated an effective means of weight loss that results in improved pregnancy outcomes for both mother and baby. This study intends to determine if substantial pre-conception weight loss, achieved using a VLED, improves pregnancy outcomes for mother and baby when compared with standard care. This research will potentially change clinical care of an obese woman planning pregnancy.

TRIAL REGISTRATION

ANZCTR, 12,614,001,160,628 . Registered on 5 November 2014.

Pre-analytical and analytical aspects affecting clinical reliability of plasma glucose results

The measurement of plasma glucose (PG) plays a central role in recognizing disturbances in carbohydrate metabolism, with established decision limits that are globally accepted. This requires that PG results are reliable and unequivocally valid no matter where they are obtained. To control the pre-analytical variability of PG and prevent in vitro glycolysis, the use of citrate as rapidly effective glycolysis inhibitor has been proposed. However, the commercial availability of several tubes with studies showing different performance has created confusion among users. Moreover, and more importantly, studies have shown that tubes promptly inhibiting glycolysis give PG results that are significantly higher than tubes containing sodium fluoride only, used in the majority of studies generating the current PG cut-points, with a different clinical classification of subjects. From the analytical point of view, to be equivalent among different measuring systems, PG results should be traceable to a recognized higher-order reference via the implementation of an unbroken metrological hierarchy. In doing this, it is important that manufacturers of measuring systems consider the uncertainty accumulated through the different steps of the selected traceability chain. In particular, PG results should fulfil analytical performance specifications defined to fit the intended clinical application. Since PG has tight homeostatic control, its biological variability may be used to define these limits. Alternatively, given the central diagnostic role of the analyte, an outcome model showing the impact of analytical performance of test on clinical classifications of subjects can be used. Using these specifications, performance assessment studies employing commutable control materials with values assigned by reference procedure have shown that the quality of PG measurements is often far from desirable and that problems are exacerbated using point-of-care devices.

Traceability Assessment and Performance Evaluation of Results for Measurement of Abbott Clinical Chemistry Assays on 4 Chemistry Analyzers

Context.—The traceability of clinical results to internationally recognized and accepted reference materials and reference measurement procedures has become increasingly important. Therefore, the establishment of traceability has become a mandatory requirement for all in vitro diagnostics devices.

Objectives.—To evaluate the traceability of the Abbott Architect c8000 system (Abbott Laboratories, Abbott Park, Illinois), consisting of calibrators and reagents, across 4 different chemistry analyzers, and to evaluate its general performance on the Toshiba 2000FR NEO (Toshiba Medical Systems Corporation, Otawara-shi, Tochigi-ken, Japan).

Design.—For assessment of traceability, secondary reference materials were evaluated 5 times, and then bias was calculated. Precision, linearity, and carryover were determined according to the guidelines of the Clinical and Laboratory Standards Institute (Wayne, Pennsylvania).

Results.—The biases from 4 different analyzers ranged from −2.33% to 2.70% on the Toshiba 2000FR NEO, −2.33% to 5.12% on the Roche Hitachi 7600 (Roche Diagnostics International, Basel, Switzerland), −0.93% to 2.87% on the Roche Modular, and −2.16% to 2.86% on the Abbott Architect c16000. The total coefficients of variance of all analytes were less than 5%. The coefficients of determination (R2) were more than 0.9900. The carryover rate ranged from −0.54% to 0.17%.

Conclusions.—Abbott clinical chemistry assays met the performance criteria based on desirable biological variation for precision, bias, and total error. They also showed excellent linearity and carryover. Therefore, these clinical chemistry assays were found to be accurate and reliable and are readily applicable on the various platforms used in this study.

Role and Responsibilities of Laboratory Medicine Specialists in the Verification OF Metrological Traceability of in vitro Medical Diagnostics

To be accurate and equivalent, laboratory results should be traceable to higher-order references. Furthermore, their quality should fulfill acceptable measurement uncertainty as defined to fit the intended clinical use. With this aim, in vitro diagnostics (IVD) manufacturers should define a calibration hierarchy to assign traceable values to their system calibrators and to fulfill during this process uncertainty limits for calibrators, which should represent a proportion of the uncertainty budget allowed for clinical laboratory results. It is therefore important that, on one hand, the laboratory profession clearly defines the clinically acceptable uncertainty for relevant tests and, on the other hand, end-users may know and verify how manufacturers have implemented the traceability of their calibrators and estimated the corresponding uncertainty. Important tools for IVD traceability surveillance are quality control programmes through the daily verification by clinical laboratories that control materials of analytical systems are in the manufacturer’s declared validation range [Internal Quality Control (IQC) component I] and the organization of External Quality Assessment Schemes meeting metrological criteria. In a separate way, clinical laboratories should also monitor the reliability of employed commercial systems through the IQC component II, devoted to estimation of the measurement uncertainty due to random effects, which includes analytical system imprecision together with individual laboratory performance in terms of variability.