Gestational diabetes in a tertiary care hospital: implications of applying the IADPSG criteria.

BACKGROUND: The American Diabetes Association has endorsed the International Association of Diabetes and Pregnancy Groups (IADPSG) recommendation that every pregnant woman should undergo the 75 g oral glucose tolerance test (OGTT) to screen for gestational diabetes mellitus (GDM). PURPOSE: To find the cost and workload implications of switching from the current two-step screening of GDM to the one-step IADPSG approach. METHODS: The cost (US $) and laboratory workload units (WLU) were calculated for three possible strategies: (1) 50 g glucose screen, if positive, followed by the 100 g OGTT; (2) universal 75 g OGTT; and (3) screening with the initial fasting plasma glucose of the OGTT. RESULTS: For the 1,101 pregnant women screened in 1 year, the cost of the three strategies was $ 31,985, $ 55,250 and $ 35,875, respectively; the laboratory burden was 28,975 WLU, 18,662 WLU and 12,215 WLU, respectively. CONCLUSIONS: Switching to the one-step, strategy 2 (IADPSG) would increase the cost by 42 % but decrease the laboratory workload by 36 % compared to the two-step, strategy 1. However, an initial screen by the fasting plasma glucose of the OGTT is the ideal strategy, both in terms of cost and laboratory workload.

Gestational diabetes: an evaluation of serum fructosamine as a screening test in a high-risk population.

AIM: To evaluate the value of serum fructosamine as a screening test for gestational diabetes mellitus (GDM). METHODS: 849 pregnant women underwent the one-step 75 g oral glucose tolerance test (OGTT) for universal screening of GDM. The fasting serum fructosamine (cFruc) was assessed using the area under the receiver operating characteristic curve (AUC). The GDM diagnostic criteria used were those of the American Diabetes Association; however, the cFruc performance was also evaluated using criteria of the World Health Organization, Australian (ADIPS), European (EASD) and International Association of Diabetes and Pregnancy Study Groups (IADPSG). RESULTS: 113 (13.3%) women had GDM. The AUC of the cFruc was 0.60 (95% CI 0.54-0.66). A cFruc threshold of 237 µmol/l achieved an acceptable sensitivity of 85.8% (95% CI 78.0-91.0%), but the associated specificity remained poor at 23.4% (95% CI 20.0-27.0%) with a positive predictive value of just 14.7%. Overall, over 4 out of 5 pregnant women, being over this cutoff, would need the confirmatory OGTT. No cFruc threshold reached acceptable likelihood ratios to rule-in or rule-out GDM. The AUC for cFruc remained unacceptable independent of the diagnostic criteria. CONCLUSIONS: Despite all the advances in technology, serum fructosamine is a poor test to screen for GDM.

Gestational diabetes: using a portable glucometer to simplify the approach to screening.

BACKGROUND: In populations at a high-risk for gestational diabetes (GDM), the recommendation of screening every pregnant woman with the oral glucose tolerance test (OGTT) is very demanding. AIM: To assess the usefulness of the portable, plasma optimized glucometer in simplifying the approach to screening of GDM. METHODS: 1,662 pregnant women underwent the one-step 75 g OGTT for routine screening of GDM, as defined by the criteria of the American Diabetes Association. The glucometer was used to measure the initial fasting venous whole blood glucose (FBG) to assess its value as a screening test in predicting the need to proceed with the OGTT. RESULTS: 186 (11.2%) women had GDM. The area under the receiver operating characteristic curve (AUC) of the FBG was 0.876 (95% CI 0.847-0.906). A FBG threshold (at an acceptable sensitivity of 85%) independently could 'rule-out' GDM in 1,138 (68.5%) women; i.e. over two-thirds of the women would not need to continue with the cumbersome OGTT. CONCLUSIONS: Using the glucometer to initially measure the venous FBG as a screen can help to significantly reduce the number of OGTTs needed for the diagnosis of GDM. This algorithm offers a simple, practical, cost-effective and patient-friendly approach for the screening of GDM.

Gestational diabetes: fasting and postprandial glucose as first prenatal screening tests in a high-risk population.

OBJECTIVE: To evaluate the value of fasting (FPG) and 2-hour postprandial (PPG) plasma glucose as screening tests for gestational diabetes mellitus (GDM) in a high-risk population during early pregnancy. STUDY DESIGN: At their first prenatal visit, 708 women underwent FPG and PPG for universal screening for GDM, with the diagnosis confirmed by the 75-g oral glucose tolerance test (World Health Organization criteria). The area under the receiver operating characteristic curve (AUC) was used to analyze the performance of the 2 screening tests. RESULTS: Of 184 (25.9%) women with GDM, 79 (42.9%) were identified before 18 weeks. The AUC for FPG to predict GDM was 0.579 (95% CI 0.531-0.627). Though a threshold of 85 mg/dL achieved minimally acceptable sensitivity, 79.9%, the corresponding specificity remained poor, 27.5%, with a false positive rate (FPR) of 72.5%. The AUC for PPG was 0.717 (95% CI 0.670-0.765); a cutoff of 95 mg/dL achieved a sensitivity of 79.9% and FPR of 53.1%. CONCLUSION: Though GDM could be diagnosed in > 40% women in early pregnancy at their first prenatal visit, the poor specificity and high FPR of FPG and PPG, alone or in combination, make them unsuitable screening tests for GDM.

Thyroid hormone reference intervals in an ambulatory Arab population on the Abbott Architect i2000 immunoassay analyzer.

BACKGROUND: Considerable differences in reference intervals for FT4 and TSH have been reported between countries. Method related differences in the distribution of free thyroxine (FT4) have also been reported. The aim of this study was to establish reference intervals for thyrotrophin (TSH) and FT4 in an ambulatory adult (16-75 y) Arab population attending a general practice clinic using the Abbott Architect i2000 immunoassay analyzer. METHODS: TSH and FT4 results from 959 consecutive ambulatory Arab subjects were available. After excluding data sets from pregnant women, patients with known and newly diagnosed thyroid disease, individuals taking medication that may affect TSH and FT4 and individuals with acute illness, 742 data sets were available for analysis. A 2-way between-groups ANOVA was conducted to explore the impact of age and gender on TSH and FT4. RESULTS: TSH showed a non-Gaussian distribution, FT4 showed a near normal distribution. There was no significant main effect on FT4 and TSH for age and gender. The interaction effect of age and gender also did not reach significance. The 95% reference intervals were: TSH 0.30-4.32 mU/l and FT4 9.8-18.6 pmol/l. The reference intervals for TSH and FT4 determined in this study differed from those reported from other countries using the same analytical platform and from the 99% reference intervals, provided by the manufacturer. CONCLUSIONS: These differences in reference intervals in different populations may affect patient management. The data reported reemphasize that each laboratory should determine population and method-specific reference intervals.

Thyrotrophin and free thyroxine trimester-specific reference intervals in a mixed ethnic pregnant population in the United Arab Emirates.

BACKGROUND: Physiological alterations in the homeostatic control of thyroid hormones cause changes in thyroid function tests in pregnant women. A lack of method, trimester and population-specific reference intervals for free thyroxine (FT4) and thyrotrophin (TSH) makes interpretation of FT4 and TSH levels in pregnancy difficult. We established trimester-specific reference intervals for TSH and FT4 in a mixed ethnic population of pregnant women attending two antenatal clinics in the United Arab Emirates. METHODS: TSH and FT4 result from 1140 women with uncomplicated singleton pregnancy were available. The 95% reference intervals were determined for TSH and FT4 for each trimester for Arab women from the United Arab Emirates and other Arab countries and Asian women. RESULTS: Suppressed TSH levels in the first trimester recovered to non-pregnant levels in the third trimester. There was a significant difference in TSH levels between trimesters 1 and 2, and 2 and 3 (p<0.0005). There was no significant difference in the TSH levels between the various ethnic groups. Mean FT4 levels decreased with each progressive trimester in all groups. There were significant differences in FT4 levels between all three trimesters (p<0.005), especially between the first and second trimesters. FT4 differed significantly between UAE nationals and Asians in the first and second trimesters (p<0.005). CONCLUSIONS: In general, the findings were in keeping with earlier reports. Use of trimester-specific reference intervals should help in the appropriate interpretation of thyroid hormone results in the mixed UAE population.

HbA1c: a comparison of NGSP with IFCC transformed values.

BACKGROUND: An approved IFCC reference method for measuring HbA1c, with a firm and reproducible correlation with NGSP values, is now available. We established (i) the degree of agreement of HbA1c results between the NGSP-certified and the IFCC-calibrated (converted to NGSP values) immunochemical method and (ii) the difference in the classification of control of diabetes mellitus (DM) in individual patients between the methods. METHODS: HbA1c was measured on the same hemolysate from each patient by both methods (n=92). Results were analyzed by the kappa statistic, linear regression, and McNemar's chi(2) test. RESULTS: Both methods achieved acceptable analytical performance. The kappa statistic measure of agreement was 0.65 and r(2)=0.937. Overall, 21 (22.8%) patients were classified differently in the extent of diabetes control (good, acceptable, or poor), with a significant difference between the 2 methods (p<0.0005). CONCLUSIONS: The IFCC converted to NGSP values were significantly different from the previously used NGSP-certified method. The differences between the 2 methods are of sufficient magnitude that HbA1c results from these methods are not interchangeable. The IFCC method being scientifically superior in concept and design should replace the NGSP method. New HbA1c targets for DM management need to be established for the IFCC method.

Gestational diabetes in a high-risk population: using the fasting plasma glucose to simplify the diagnostic algorithm.

OBJECTIVE: To evaluate the value of fasting plasma glucose (FPG) in screening a high-risk population for gestational diabetes mellitus (GDM). STUDY DESIGN: During an 8-month period, 1685 pregnant women underwent the one-step 75 g oral glucose tolerance test (OGTT) as a part of a universal screening program. The receiver operating characteristic (ROC) curve was used to analyze the performance of the FPG. RESULTS: 333 (19.8%) women had GDM (WHO criteria). The area under the ROC curve of FPG to detect GDM was 0.639 (95% CI 0.603-0.674), which reflected the degree of the FPG histogram overlap in women with and without GDM. A FPG threshold of 4.7 mmol/l reached the minimally acceptable sensitivity of 78.1% with a corresponding unacceptable specificity of 32.2%. 508 (31%) women were below this threshold, at a negative predictive value of 85.6%. The FPG at higher thresholds with acceptable specificity had poor sensitivity and positive predictive value to be useful. CONCLUSION: Though the high false positive rate at any FPG threshold with adequate sensitivity makes the FPG an inappropriate test for GDM screening, the FPG has the potential to avoid nearly one-third of the cumbersome OGTTs at the expense of missing one-fifth of pregnant women with milder GDM.

Evaluation of a glucose meter against analytical quality specifications for hospital use.

BACKGROUND: The value of glucose meters in point of care testing (POCT) by medical professionals and self monitoring of blood glucose (SMBG) by patients is well established. We evaluated the SureSteppFlexx glucose meter against objective targets for imprecision and total error (TE). METHODS: The SureStepFlexx blood glucose system uses a reflectance-based glucose oxidase (GO) method and reports plasma-equivalent glucose values. The reference method was the Beckman LX20 Pro glucose oxidase/oxygen electrode method. Patient samples and commercial aqueous, quality control (QC) material were used to assess imprecision. To determine total error of the meters, results obtained on patient heparinized blood were compared against results obtained by the reference method using plasma. Analyses were carried out by an experienced nurse and technologist. RESULTS: Both operators achieved imprecision of < or =5% for all measurements. Overall, the percentage of results deviating from the total error targets were 0-21% and 4-13% for the nurse and technologist, respectively. Compared with earlier studies, the percentages of reported results outside the < or =10% and < or =5% American Diabetes Association (ADA) criteria are significantly lower. CONCLUSIONS: The SureSteppFlexx glucose meter meets analytical quality requirements and is suitable for POCT use in our hospital. We propose a tiered approach and suggest minimum, desirable and optimum total error targets for glucose meters of < or =5%, 7.9% and 13%, respectively.

Evaluation of HbA1C results in an external quality assessment scheme in South Africa.

BACKGROUND: Measuring HbA1c blood levels allows us to assess average glycaemia in individuals during the preceding 6-8 weeks. There is a clear association between increasing risk of complications with higher HbA1c values and a significant risk reduction of the complications with lower HbA1c values. METHODS: The performance of South African laboratories in an External Quality Assurance scheme for HbA1c is reported. CONCLUSIONS: A number of laboratories and methods do not meet the required analytical standards. South African laboratories should adopt measures similar to other regional and national initiatives to significantly improve laboratory performance and bring about harmonization of HbA1c assays.

Biological variation in sweat sodium chloride conductivity.

BACKGROUND: Sweat conductivity, which is equivalent to sweat NaCl concentration, is used as a screening test to identify possible cystic fibrosis (CF) patients. No data exist on the biological variation of this variable and the influence it may have on the interpretation of sweat testing. The aim of this study was to determine the components of biological variation for sweat sodium chloride conductivity and to apply biological variation parameters in the interpretation of sweat conductivity. METHODS: Sweat conductivity was determined once a week for 5 consecutive weeks on 15 healthy volunteers, 20 healthy infants and 20 known CF patients. RESULTS: The analytical coefficient of variation (CV(A)) was 1.15% for the high-level control material, with a value of 123 mmol/L, and 1.32% for the normal-level control material with a value of 40 mmoL/L. The within-subject (CV) and between-subject (CV(G)) biological variations were 12.0% and 30.0%, respectively, for healthy controls; 18% and 20% for healthy infants; and 7.3% and 6.5% for CF patients, respectively. Using the CV(A), CV(G) and CV(I), the 95% reference ranges were determined for the above-mentioned three groups. The calculated 95% ranges for the healthy babies and CF patients were 18-60 mmoL/L and 96-144 mmoL/L. CONCLUSIONS: Our data support a decision level of > 60 mmoL/L for confirmatory CF testing. A lower decision level will result in an unacceptable high rate of unnecessary confirmation testing.

Gestational diabetes: implications of variation in post-partum follow-up criteria.

OBJECTIVE: To compare the recommendations of the American Diabetes Association (ADA) with the World Health Organization (WHO) for evaluating women with gestational diabetes (GDM) after delivery. STUDY DESIGN: During a 5-year period, 549 patients underwent the 2h, 75 g oral glucose tolerance test (OGTT), 4-8 weeks after delivery. They were classified by the criteria of WHO (1985), the ADA [1997, fasting glucose (FPG)] and the revised WHO (1999). RESULTS: The prevalence of diabetes by WHO-1985 and ADA-1997 were similar (8.2% versus 6.6%) but estimates of impaired glucose homeostasis varied widely (15.5% impaired glucose tolerance (IGT) versus 9.3% impaired fasting glucose, respectively). 118 (21.5%) women and 83 (15.1%) women showed a classification discrepancy between ADA-1997 with the WHO-1985 and -1999, respectively. The receiver-operating characteristic (ROC) curve area of the FPG was 0.94 for DM by the OGTT (WHO-1985 criteria) but only 0.59 for IGT by the 2h post-glucose. CONCLUSIONS: The various guidelines for GDM follow-up after delivery, often based on expert opinion, produce similar estimates for diabetes prevalence but widely discordant results for glucose intolerance. Until more uniform evidence-based criteria become available, the various strategies for GDM follow-up will continue to cause confusion in clinical practice.

Dynamics of brain natriuretic peptide in critically ill patients with severe sepsis and septic shock.

PURPOSE: Changes of B-type natriuretic peptide (BNP) in sepsis and its utility in predicting intensive care unit outcomes remains a conflicting issue. To investigate the changes in plasma levels of BNP in patients with severe sepsis/septic shock and to study the association of BNP levels with the severity of the disease and prognosis of those patients. METHODS: Thirty patients with severe sepsis or septic shock were enrolled in our study. BNP measurements and echocardiography were carried out on admission and on 4(th) and 7(th) days. Blood concentrations of BNP were measured by commercially available assays (Abbott methods). In-hospital mortality and length of stay were recorded multivariate analyses adjusted for acute physiology and chronic health evaluation score II (APACHE II score) was used for mortality prediction. RESULTS: Twenty patients admitted with the diagnosis of severe sepsis and 10 patients with septic shock. The in-hospital mortality was 23.3% (7 patients). Admission BNP was significantly higher in the non-survivors 1123±236.08 versus 592.7±347.1 (P<0.001). By doing multivariate logestic regression, the predicatable variables for mortality was APACHE II score, BNP, and then EF. CONCLUSION: BNP concentrations were increased in patients with severe sepsis or septic shock and poor outcome was associated with high BNP levels; thus, it may serve as a useful laboratory marker to predict survival in these patients.

Performance of the Roche Accu-Chek active glucose meter to screen for gestational diabetes mellitus using fasting capillary blood.

BACKGROUND: Point-of-care (POC) blood glucose measurement using glucose meters is used by diabetes patients to mange their disease. POC glucose testing also is also used in tight glycemic control protocols and as a screening tool for diabetes. We report the performance and effectiveness of the Accu-Chek® Active (Roche Diagnostics GmbH, Mannheim, Germany) glucose meter to screen for gestational diabetes mellitus (GDM) using blood fasting capillary glucose (FCG). METHODS: To screen for GDM, 1,465 pregnant women underwent an oral glucose glucose tolerance test. Correlation between the FCG and fasting plasma glucose (FPG) levels was determined by Passing and Bablok regression analysis. Total error (TE) of the glucometer was ascertained using the Bland-Altman method with the DXC-800 analyzer (Beckman-Coulter Instruments, Brea, CA) as the reference method. The area under the receiver operator characteristic curve was used to analyze the performance of the FCG to predict GDM. RESULTS: FPG and FCG identified 361 (24.6%) and 338 (23%) women as having GDM, respectively. The Bland-Altman TE at 95% limits of agreement was -11.1% to 10.8%. The area under the receiver operator characteristic curve was 0.953 (95% confidence interval 0.943 to 0.964). CONCLUSIONS: The Roche Accu-Chek Active glucometer meets analytical and clinical quality requirements. A TE of±15% is acceptable for glucose meters used in ambulatory care, including home self-monitoring of blood glucose, and different TE targets should be set for acute critical care settings.

Gestational diabetes mellitus: simplifying the international association of diabetes and pregnancy diagnostic algorithm using fasting plasma glucose.

OBJECTIVE: To determine the impact of the International Association of Diabetes and Pregnancy Study Group (IADPSG) criteria on 1) gestational diabetes mellitus (GDM) diagnosis compared with the American Diabetes Association (ADA) criteria and 2) the fasting plasma glucose (FPG) to predict GDM. RESEARCH DESIGN AND METHODS: In 10,283 pregnant women undergoing a 75-g oral glucose tolerance test (OGTT) for universal screening of GDM, two FPG thresholds (of the OGTT) were used to rule in and to rule out GDM. RESULTS: The IADPSG and ADA criteria identified GDM in 3,875 (37.7%) women and 1,328 (12.9%) women, respectively (P < 0.0005). FPG thresholds of >or=5.1 mmol/l ruled in GDM in 2,975 (28.9%) women with 100% specificity, while <4.4 mmol/l ruled out GDM in 2,228 (21.7%) women with 95.4% sensitivity. FPG independently could have avoided the OGTT in 5,203 (50.6%) women. CONCLUSIONS: The IADPSG criteria increased GDM prevalence nearly threefold. By circumventing a significant number of OGTTs, an initial FPG can greatly simplify the IADPSG diagnostic algorithm.

Impact of a satellite laboratory on turnaround times for the emergency department.

BACKGROUND: Prolonged laboratory turnaround time (TAT) contributes to prolonged length of stay in emergency departments (EDs). The TAT of laboratory test results is a common key performance indicator by which clinicians and regulatory bodies evaluate laboratory performance. Establishing satellite laboratories in EDs staffed by laboratory technologists is one approach towards reducing TAT. METHODS: TAT data were collected for three time intervals: (a) sampling time to time samples received in the laboratory (transportation time), (b) sample received in the laboratory until results were available for viewing on the laboratory information system monitor or collection by ED staff (within laboratory TAT), and (c) sampling to availability of results (total TAT, e.g., a+b). The target was to achieve a median within laboratory TAT of 45 min for samples received from the ED. RESULTS: The median transportation times for samples to be delivered to the central and satellite laboratory were 22 min and 1 min, respectively (p<0.0001). The median within laboratory TATs were 45 [95% confidence interval (CI) 43-49] and 34 (95% CI 33-35) min for the central and satellite laboratories, respectively (p<0.001). CONCLUSIONS: A satellite laboratory in the ED can significantly reduce laboratory TAT.

Fasting plasma glucose as a screening test for gestational diabetes mellitus.

Although debated, most preeminent expert panels recommend routine screening for gestational diabetes mellitus (GDM). Among the many tests that have been used and evaluated for the screening of GDM, the fasting plasma glucose (FPG) remains very appealing. It is easy to administer, well tolerated, inexpensive, reproducible and patient friendly. However attractive, the FPG has given varied results in different populations and its use as a screening test for GDM remains uncertain. This review will objectively assess the available studies to find the real value of FPG as a screening test for GDM.

Implementing the Stockholm Conference hierarchy of objective quality criteria in a routine laboratory.

BACKGROUND: Analytical performance of clinical laboratory testing should be evaluated against objective quality specifications. The Stockholm Conference consensus recommendation states that from a hierarchy of quality models, the highest-ranking model should be used. This study reports the performance of a routine clinical laboratory using these quality recommendations. Quality standards recommended for use in manufacturers' package inserts are also compared against the objective criteria. METHODS: Imprecision of 22 analytes was monitored by analyzing three levels of commercial quality control (QC) material daily over a 6-month period. The performance for each analyte was evaluated against defined quality specifications based on biological variation and the National Cholesterol Education Panel (NCEP) criteria. RESULTS: Overall, objective quality specifications were met by the laboratory for 18/22 (82%) analytes. The performance for analytes not meeting the criteria was assessed against quality targets based on a model lower in the hierarchy, i.e., interlaboratory imprecision data derived from an accredited EQA program. All analytes met these quality targets. When quality targets set by the manufacturer were applied to biological variation and NCEP criteria, results for only 8/22 (36%) analytes met the targets. CONCLUSIONS: Objective quality specifications can be consistently achieved in a routine laboratory. The hierarchy model of the Stockholm Conference should be promoted for global adoption.