The use of fructosamine in cystic fibrosis-related diabetes (CFRD) screening.

OBJECTIVE: To determine whether serum fructosamine correlates with glycemic control and clinical outcomes in patients being screened for cystic fibrosis-related diabetes (CFRD). METHODS: Fructosamine and percent predicted forced expiratory volume in 1s (FEV1) were measured in patients undergoing a 2h oral glucose tolerance test (OGTT) for CFRD screening. Fractional serum fructosamine (FSF) was calculated as fructosamine/total protein. RESULTS: FSF exhibited a positive correlation with 2h OGTT results (r2=0.3201, p=0.009), and ROC curve analysis suggested that FSF can identify patients with an abnormal OGTT (AUC=0.840, p=0.0002). FSF also exhibited a negative correlation with FEV1 (r2=0.3732, p=0.035). Patients with FSF≥3.70µmol/g had significantly lower FEV1 (median 47%) compared to those with FSF<3.70µmol/g (median 90%; p=0.015). CONCLUSIONS: FSF correlated with both OGTT results and FEV1, and reliably identified patients with abnormal OGTT results. This simple blood test shows potential as an effective tool in CFRD screening.

Stability of specific IgE antibodies to common food and inhalant allergens.

OBJECTIVE: To determine the optimum storage temperature for serum allergen specific IgE antibodies (sIgE) to common food and inhalant allergens. METHODS: Patient sera with sIgE concentrations ≥0.7kIUA/l were pooled accordingly: pool 1-peanut and hazelnut, pool 2-egg white, cow's milk and cod fish, pool 3-soy, wheat and shrimp and pool 4-dust mite Dermatophagoides farinae, dog dander, cat dander, Timothy grass pollen, and silver birch pollen. Aliquots stored frozen, refrigerated and at room temperature were tested in duplicate (Phadia ImmunoCAP® 250) over two weeks. The relative difference was calculated for each sIgE as a percentage of the initial value and compared to the analytical reference change value. RESULTS: Minimal effects on specimen stability were noted for all sIgE analyzed under the three storage conditions tested in this study. All changes observed in sIgE concentrations were related to the assay variability and not to sample deterioration. CONCLUSION: Serum allergen specific IgE concentrations are stable at all temperatures studied for up to 17days.

Identification of Hb Wayne and its effects on HbA1c measurement by 5 methods.

BACKGROUND: The World Health Organization and the American and Canadian Diabetes Associations approved HbA1c >6.5% as diagnostic for type 2 diabetes mellitus (T2DM). Hb variants and/or their chemically modified species can interfere with HbA1c measurements. We recently described a patient with Hb Wayne trait who was misdiagnosed with T2DM based on falsely elevated HbA1c. Hb Wayne is a clinically silent variant that exists as two isoforms: Hb Wayne I (Asn 139) and Hb Wayne II (Asp 139). METHODS: Hemoglobinopathy investigation was performed by HPLC (Bio-Rad VARIANT-II), alkaline and acid electrophoresis (Sebia Hydrasis2), capillary zone electrophoresis (Sebia CAPILLARYS2™) and DNA sequencing. HbA1c was measured by five methods. RESULTS: Hb Wayne eluted as two small fractions with retention times of 1.0 and 1.46min on the HPLC (Bio-Rad VARIANT-II). Alkaline gel and capillary electrophoresis showed two small bands migrating faster than HbA. Hb Wayne generated spuriously high results on the Bio-Rad VARIANT-II Turbo 2.0, no results on the Tosoh G8, and did not interfere with either the Sebia CAPILLARYS2™ or immunoassays from Roche (tinaquant) and Siemens (Bayer DCA2000+). Based on the Hb Wayne HPLC profile of 3 patients, an algorithm was developed to facilitate its detection, which identified 9 additional patients with Hb Wayne trait. CONCLUSIONS: We characterize Hb Wayne by chromatographic and electrophoretic techniques and show the effect of Hb Wayne on five common HbA1c methodologies. We developed a quality assurance tool to assist in detecting Hb Wayne trait during HbA1c analysis on the Bio-Rad VARIANT-II™ Turbo 2.0.

A novel double heterozygous Hb Fontainebleau/HbD Punjab hemoglobinopathy.

OBJECTIVES: To report the finding of a novel double heterozygous hemoglobinopathy, the coinheritance of Hb Fontainebleau (α-chain variant) with HbD-Punjab (ß-chain variant) discovered upon investigation of unexplained microcytosis in an infant. DESIGN AND METHODS: Hemoglobinopathy investigation was performed by high performance liquid chromatography (HPLC) using the ß-thalassemia Short Program on the Bio-Rad Variant II(TM) followed by gel electrophoresis at alkaline and acid pH (Sebia Hydrasys 2 Electrophoresis System) and molecular diagnostic testing. This study complied with our institutional board ethics requirements. RESULTS: HPLC and electrophoresis suggested a complex α- and ß-chain hemoglobinopathy with presumptive identification of the beta Hb variant as Hb D-Punjab. DNA sequencing analysis revealed the presence of a double heterozygous status for Hb Fontainebleau/Hb D-Punjab. CONCLUSIONS: In this paper we report the coinheritance of Hb Fontainebleau with Hb D-Punjab.

Incidence of hemoglobinopathies and thalassemias in Northern Alberta. Establishment of reference intervals for HbF and HbA2.

OBJECTIVES: The aims of this study were to identify the incidence of hemoglobinopathies and thalassemias in Northern Alberta and calculate the reference intervals (RI) for hemoglobin (Hb) HbF and HbA2. METHODS: A retrospective ad-hoc analysis of the structural Hb variants and thalassemias identified on patients who had a hemoglobinopathy/thalassemia investigation performed between February 1 to December 31, 2013. Results were extracted from the Laboratory Information System. Statistical analysis was performed using MedCalc® version 11.4.2.0 for Windows software. RESULTS: 6616 hemoglobinopathy/thalassemia investigations and HbS screens were physician requested and 602 Hb variants were fortuitously found during HbA1c analysis. 3438 were interpreted as "normal" and 532 were classified as iron deficient. 3306 individuals, with age ranging from 3 to 92 years were included in the RI calculation. HbA2 RI was 2.3% to 3.4% and HbF 0.0% to 1.8%. 524 and 423 α and ß thalassemia traits respectively were identified. Additionally ten 뫧 thalassemia traits and twelve cases of HbH disease were identified. Regarding hemoglobinopathies, 7% were classified as α-chain variants and 93% as ß-chain variants with HbS (46%), HbE (16%), HbD Punjab (8%) and HbC (7%) traits being the most prevalent. We also documented 20 homozygous hemoglobinopathies and 36 compound/double heterozygous hemoglobinopathies. CONCLUSION: A wide diversity of hemoglobinopathies is found in the Northern Alberta population, 80% of the hemoglobinopathies were found as a reflex to HbA1c testing. Reference intervals for HbF and HbA2 were established.

Current evidence and future perspectives on the effective practice of patient-centered laboratory medicine.

BACKGROUND: Systematic evidence of the contribution made by laboratory medicine to patient outcomes and the overall process of healthcare is difficult to find. An understanding of the value of laboratory medicine, how it can be determined, and the various factors that influence it is vital to ensuring that the service is provided and used optimally. CONTENT: This review summarizes existing evidence supporting the impact of laboratory medicine in healthcare and indicates the gaps in our understanding. It also identifies deficiencies in current utilization, suggests potential solutions, and offers a vision of a future in which laboratory medicine is used optimally to support patient care. SUMMARY: To maximize the value of laboratory medicine, work is required in 5 areas: (a) improved utilization of existing and new tests; (b) definition of new roles for laboratory professionals that are focused on optimizing patient outcomes by adding value at all points of the diagnostic brain-to-brain cycle; (c) development of standardized protocols for prospective patient-centered studies of biomarker clinical effectiveness or extraanalytical process effectiveness; (d) benchmarking of existing and new tests in specified situations with commonly accepted measures of effectiveness; (e) agreed definition and validation of effectiveness measures and use of checklists for articles submitted for publication. Progress in these areas is essential if we are to demonstrate and enhance the value of laboratory medicine and prevent valuable information being lost in meaningless data. This requires effective collaboration with clinicians, and a determination to accept patient outcome and patient experience as the primary measure of laboratory effectiveness.

Analytical evaluation of the Diazyme glycated serum protein assay on the siemens ADVIA 1800: comparison of results against HbA1c for diagnosis and management of diabetes.

Hemoglobin A1c (HbA1c) is considered the gold standard for assessment of glycemic control in diabetic patients. HbA1c is inadequate in individuals homozygous or compound heterozygous for hemoglobin variants or in conditions with an altered red blood cell turnover. In these cases glycated albumin (GA) is proposed as an alternative assay. We aimed to evaluate the analytical performance of the Diazyme glycated serum protein (GSP) assay on an automated analyzer, to establish a reference interval (RI), and to compare from a clinical perspective, GSP/GA with glycated Hb (glyHb) results. Validation studies followed the CLSI guidelines and included precision, linearity, interferences, concordance of results with glyHb, and RI calculation. GSP was analyzed on representative samples with previously ordered HbA1c and albumin from the Dyna LIFE : DX laboratory. Samples from patients with bisalbuminemia, hemoglobinopathies, and multiple myeloma were also included. Within-run and total imprecision was <3.0% at both levels of control, analytical sensitivity was 5.31 µmol/L, and linearity was verified from 10 to 1150 µmol/L (total allowable error of 5%). Clinical concordance between %GA and glyHb was substantial (n = 175, R2 = .91, kappa = .78, P = .167). GSP RI was 160 to 340 µmol/L or if expressed as %GA 10.5 to 17.5%. Analytical performance of the Diazyme GSP assay on the Siemens ADVIA 1800 is acceptable for clinical use. The RI obtained was higher than that suggested by the manufacturer.

The effect of paraproteins and rheumatoid factor on four commercial immunoassays for vancomycin: implications for laboratorians and other health care professionals.

BACKGROUND: Paraproteins, immunoglobulins (Igs), which are elevated in various autoimmune disorders, are known to interfere with various laboratory immunoassays, including vancomycin (VANC). Rheumatoid factor (RF), a known immunoassay interferant, may cause falsely elevated results. OBJECTIVES: The aims of this study were to (1) evaluate the effect of 3 paraproteins (IgA, IgG, and IgM) on 4 commercial VANC immunoassays [fluorescence polarization immunoassay; enzyme multiplied immunoassay; 2 particle-enhanced turbidimetric inhibition immunoassays]; (2) determine the concentration at which the effect is obtained, and (3) examine the influence of RF on the VANC methods. METHOD: Serum and plasma pools from patients prescribed VANC and a spiked VANC pool (20 mg/L) were each mixed 1:1 with individual patient specimens containing IgA (6-63 g/L), IgG (6-54 g/L), IgM (3-30 g/L) (n = 4 for each Ig), and a patient RF pool (196 IU/L). The mixtures (n = 39) were split and distributed for VANC analysis. RESULTS: IgA and IgG in serum and plasma did not affect any of the VANC immunoassays. RF added to plasma specimens did not interfere, but in serum, elevated VAN results were observed. IgM did not affect the fluorescence polarization immunoassay and enzyme multiplied immunoassay methods but did attenuate VANC concentrations by both particle-enhanced turbidimetric inhibition immunoassays (Siemens, Beckman Coulter), with a more pronounced effect on the latter, producing concentrations >20% lower than expected in the patient serum and spiked plasma pools. The effect was progressively negative at effective IgM concentrations of 10 and 15 mg/L. CONCLUSIONS: This phenomenon is a major analytical and clinical issue that must be communicated to health care professionals caring for patients receiving VANC, so optimal therapy is achieved.

Is HbA1c a good screening test for diabetes mellitus?

OBJECTIVES: HbA(1c) has been recently recommended as the primary diagnostic test for diabetes. This study evaluated the positive predictive value (PPV) and negative predictive value (NPV) of HbA(1c) against the oral glucose tolerance test (OGTT) in three locations. DESIGN AND METHODS: Three years of data with concurrent OGTT and HbA(1c) tests were extracted from Laboratory Information Systems (LIS) and receiver operator (ROC) curves and positive and negative predictive values calculated comparing the OGTT with the HbA(1c) values using a 10% prevalence of diabetes. RESULTS: The recommended threshold HbA(1c) value of 6.5% did not give the optimal combination of NPV (0.93 to 0.92) and PPV (0.40 to 0.61) compared to a threshold HbA(1c) value of 7.0% (NPV 0.91 to 0.92, PPV 0.61 to 0.73). CONCLUSION: The optimal HbA(1c) value for the diagnosis of diabetes is 7.0% but even at this HbA(1c) the PPV is suboptimal and may cause up to 12% of patients without diabetes, as defined by a normal OGTT, to be classified having diabetes mellitus.

Total hCG tests.

INTRODUCTION: There are 12 types of automated total hCG tests sold today, the Abbott Architect, Abbott AxSym, the Beckman Access 2. Beckman DxI 800, the Ortho Vitros EciQ, Roche Elecsys hCG+ß, Siemens ACS180, Siemens Centaur, Siemens Dimension, Siemens Immulite and Siemens Stratus, and the Tosoh A1A. All tests claim to be total hCG tests but do not define what total means. Total hCG test needs to detect all hCG variants in order to be used for all hCG test clinical applications. Here we assess this ability. METHODS: Coded samples of pure hCG, nicked hCG, hyperglycosylated hCG, nicked hCG missing C-terminal peptide, nicked hyperglycosylated hCG, asialo hCG, hCGß, nicked hCGß and ß-core fragment were tested blindly in serum and urine at 10 independent laboratories. RESULTS: While the Siemens Immulite total hCG test detected 8 of 9 hCG variant standards, other assays poorly detected important determinants such as nicked hCG missing the C-terminal peptide, ß-core fragment, hyperglycosylated hCG, nicked hCG, asialo hCG, and hCGß. Four assay appropriately detected 4 of 9 variants, 2 assays detected 3 of 9, 4 assays detected 2 of 9 and 1 assay only appropriately detected 1 of 7 hCG variants. DISCUSSION: Care is needed in selecting a total hCG test. The Siemens Immulite tests performed best at detecting all the hCG variants making it appropriate for all applications. Nine assays had limited applications, 3 of the assays were appropriate for advanced pregnancy testing only.

The use of serial patient blood gas, electrolyte and glucose results to derive biologic variation: a new tool to assess the acceptability of intensive care unit testing.

BACKGROUND: Most estimates of biologic variation (s(b)) are based on periodically acquiring and storing specimens, followed by analysis within a single analytic run. We demonstrate for many intensive care unit (ICU) tests, only patient results need be statistically analyzed to provide reliable estimates of s(b). METHODS: Over 11 months, approximately 28,000 blood gas measurements (including electrolyte panels and glucose) were performed on one of two Radiometer ABL800 FLEX analyzers (Radiometer, Copenhagen, Denmark) from 1676 ICU patients. We tabulated the measurements of paired intra-patient blood samples drawn within 24 h of each other. After removal of outliers, we calculated the standard deviations of duplicates (SDD) of the intra-patient pairs grouped in 2-h intervals: 0-2 h, 2-4 h, 4-6 h, … 20-22 h and 22-24 h. The SDDs were then regressed against the time intervals of 2-14 h; extrapolation to zero time represents the sum of s(b) and short-term analytic variation (s(a)). RESULTS: Substitution of experimentally derived analytic error permitted the calculation of coefficient of variation (biologic) (CV(b)) (100 s(b)/mean): pH, 0.3%; pCO(2), 5.7%; pO(2), 13%; Na(+), 0.6%; K(+), 4.8%; Cl(-), 0.8%; HCO(3)(-), 3.2%; iCa(++), 2.4%; and glucose, 10.3%. The CV(b) of the electrolytes very closely matches the lowest estimates obtained in the usual manner. CONCLUSIONS: Derivation of the ratio of biologic to analytic variation indicates that the ABL800 is extremely suitable for ICU testing. This analysis should be extended to other point of care instrument systems.

Quantification of HbA(2) in patients with and without beta-thalassemia and in the presence of HbS, HbC, HbE, and HbD Punjab hemoglobin variants: comparison of two systems.

We studied whether problems quantifying hemoglobin A(2) (HbA(2)) could be resolved by using capillary electrophoresis. HbA(2) was quantified on whole blood samples from patients with and without beta-thalassemia trait and patients heterozygous for HbE, HbS, HbC, and HbD Punjab using the VARIANT II beta-thalassemia (Bio-Rad, Hercules, CA) and Capillarys 2 (Sebia, Norcross, GA). HbA(2) results in patients with and without beta-thalassemia trait were lower with the Capillarys 2 system. Reasonable HbA(2) results were obtained for patients with HbD Punjab and HbE traits on the Capillarys 2. HbA(2) results for patients with HbS, heterozygous and homozygous, were similar by both methods. Interference due to coelution for HbA(2) results for patients with HbC trait was noted on the Capillarys 2. Between-day imprecision on the VARIANT II is less than that for the Capillarys 2 system. The Capillarys 2 is superior to the VARIANT II for quantifying HbA(2) in the presence of HbE and HbD Punjab traits. The Capillarys 2 offers only slight advantages over the VARIANT II for quantifying HbA(2) in the presence of heterozygous and homozygous HbS. The Capillarys 2 gives inferior HbA(2) results for patients with HbC trait.

MALDI-TOF MS/microwave-assisted acid hydrolysis identification of HbG Coushatta.

OBJECTIVE: To evaluate the effectiveness of microwave-assisted acid hydrolysis of proteins combined with MALDI-TOF MS to characterize hemoglobin G Coushatta. DESIGN AND METHOD: Following separation of the globin chains, the purified beta chain fractions were hydrolyzed by acid hydrolysis prior to MALDI-TOF MS. RESULTS: The method correctly identified the abnormal amino acid in HbG Coushatta. The results of this method were confirmed by an established de novo sequencing method. CONCLUSION: The correct amino acid sequence for HbG Coushatta was found. The proposed method is an alternative to MS/MS methods available for identification of abnormal hemoglobin variants.

Use of serial patient hemoglobin A1c differences to determine long-term imprecision of immunoassay and high-performance liquid chromatography analyzers.

BACKGROUND: The quality of the HbA1c assay is inversely proportional to the variation of the assay. Most published measures of HbA1c variation are limited by the data collection period, the statistical treatment of outliers, and even the noncommutability of the products used to generate the variation measurements. We have used an alternate approach to derive HbA1c variation, using serial patient data. METHODS: HbA1c measurements of outpatient blood sample pairs drawn within 30 days of each other were made on three different immunoassay systems: the Roche INTEGRA 700, the Roche INTEGRA 400, and the Dade Dimension RxL; and two high-performance liquid chromatography assays: the Tosoh G7 and the Tosoh 2.2+. The standard deviation of duplicates was calculated for the following time intervals: 1 to 3 days, 4 to 6 days, 7 to 9 days,.., 28 to 30 days. These intra-individual variations were then plotted; extrapolation to time zero yields the long term total random error which consists of both analytic and pre-analytic error. Data collection periods were usually 2 years. RESULTS: At the mean HbA1cs of 7.08%, 7.14%, 7.20%, 6.96%, and 7.51% for populations tested on the Roche INTEGRA 700, Roche INTEGRA 400, Dade Dimension RxL, Tosoh 2.2+, and Tosoh G7, respectively, the total analytic imprecisions (coefficient of variation) were 2.56%, 2.29%, 2.25%, 1.66%, and 1.14%, respectively. CONCLUSION: Assessment of the HbA1c long term total imprecisions shows that while the three immunoassay systems are acceptable, the Tosoh HbA1c analyzers demonstrate superior analytic performance.

Application of 3-D Delta check graphs to HbA1c quality control and HbA1c utilization.

Delta checking is a laboratory information system (LIS)-based tool that detects patient and laboratory quality control errors. By using hemoglobin A1c (HbA1c) data, we developed a novel approach to summarizing and presenting patient Delta values to address limitations of current Delta check algorithms. Delta values were calculated from intrapatient pairs of HbA1c (n = 55,327) measured during 2 years in a single referral or a university hospital laboratory. Three-dimensional Delta-time (DeltaT) and percentile limit graphs were constructed. Cumulative distribution function analysis was used to explore clinical utilization. The DeltaT graphs showed that HbA1c Delta values increase asymmetrically over time. Although the 2.5 to 97.5 and 5.0 to 95.0 percentile Delta check limits were similar for both sites, the referral laboratory's 0.5 to 99.5 percentile limits were wider. For acute patient care environments, we recommend limits of -3.5% and 1.8% for measurements between 0 and 60 days and -4.0% and 2.0% for measurements between 60 and 120 days. For the outpatient environment, we recommend limits of -4.2% and 2.1% and 5.0% and 2.5% for measurements between 0 and 60 days and 60 and 120 days, respectively.Delta checking can be significantly improved with customization of limits set by population and interobservation period. Because LIS systems are incapable of these customizations, customers must become advocates for these modifications.

QA aspects for HbA1c measurements.

OBJECTIVES: To provide mechanisms for evaluating HbA(1c) results that meet the criteria for review by the 2002 NACB guidelines for reporting HbA(1c) values. DESIGN AND METHODS: Complete blood count (CBC) data and comparison of obtained HbA(1c) with a calculated HbA(1c) were used to assess the validity of HbA(1c) results meeting the NACB review criteria. RESULTS: The use of CBC data and a calculated HbA(1c) were found to be useful in evaluating the validity of unusual HbA(1c) results. CONCLUSIONS: The validity of high and low HbA(1c) results can be checked by the review of CBC data and comparing a calculated HbA(1c) against the measured value.