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 ≥0.7kIU_A/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.

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.

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+β, 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, hCGβ, nicked hCGβ and β-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, β-core fragment, hyperglycosylated hCG, nicked hCG, asialo hCG, and hCGβ. 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.

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.

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.

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.

Biochemistry testing associated with pregnancy and the newborn period -- a lot has changed since you were a baby!

Everyone has been a newborn, and everyone's mother has been pregnant. Despite the commonality of these events, medical care and the clinical chemistry laboratory's role in it have changed remarkably over the last 50 years. This review is a historical overview of clinical chemistry testing that is related to pregnancy and the newborn period.

Novel method for screening for the presence of haemoglobin S in blood

A high-performance liquid chromatography (HPLC) method designed for the measurement of haemoglobin (Hb)A(1c) in blood was investigated for use as a screening method for the presence of HbS in blood. In the Bio-Rad VARIANT II HbA(1c) method, HbS was found to have a specific retention time and percentage Hb value that enabled the detection of HbS in blood. Other Hb variants did not have the same combination of retention time and percentage Hb as HbS. The HPLC method was superior to the HbS solubility test in ease of performance and readability. Also, the proposed method showed less interference than the solubility test and could be used with samples from all age groups. The proposed method takes 3 min per sample to perform and is thus suitable for large-scale screening.

Improved resolution of serum bisalbumin on electrophoresis and investigation of bisalbumin in urine

OBJECTIVES

: The aims of this study were to improve the resolution of albumin variants (bisalbumins, especially albumin Naskapi) from albumin in commercial serum protein electrophoresis systems; to compare the separation of bisalbumin from albumin on these improved methods against the recognized gold standard of capillary electrophoresis; and to investigate the presence of albumin variants in urine.

DESIGN AND METHODS

: Electrophoresis was performed using the Sebia Hydrasys 15/30 beta1beta2 system, as well as modified methods on the Sebia Hydrasys HR and the Beckman Paragon systems. The interpretation of electrophoretic gels was performed by manual visualization and densitometric scanning. Serum samples were also analyzed using capillary electrophoresis at Sebia Electrophoresé located in Paris, France. Urine samples were concentrated using Vivaproducts concentration tubes and were electrophoresed using the Sebia Hydrasys HR system.

RESULTS

: Representative gels and scans of serum samples demonstrate the improved resolution of modified electrophoresis methods compared to routine methods. The raw data from the gels and scans were compiled to calculate concordance and discordance for each method.

DISCUSSION

: The various commercial serum protein electrophoresis systems showed improved resolution using the modified methods. In comparison with capillary electrophoresis, the modified Sebia Hydrasys HR and Beckman Paragon methods using visualization demonstrated 100% concordance and thus performed equally as well as the gold standard. Urine studies found that variant albumins are also excreted in the urine in the same 50-50 ratio as that found in the serum.

Tentative identification of hemoglobin variants in the Bio-Rad VARIANT II Hb A1C method

OBJECTIVE

To evaluate if peak characteristics, the retention time, and percentage of total hemoglobin of an unknown peak on the Bio-Rad VARIANT II Hb A1c method may be used to establish a tentative identification of hemoglobin variants.

METHOD

The peak characteristics, retention time, and percentage of total hemoglobin obtained on abnormal peaks found on the Bio-Rad VARIANT II Hb A1c method were tabulated and evaluated against the identification of the hemoglobin variant established by the Bio-Rad beta thalassemia HPLC method and hemoglobin electrophoresis at both acid and alkaline pH.

RESULTS

Some hemoglobin variants show specific peak characteristics, retention times, and percentage of total hemoglobin on the Bio-Rad VARIANT II Hb A1c method that allows for tentative identification of the hemoglobin variant. The retention times and percentage of hemoglobin variant for the common hemoglobin variants E, D, S, and C obtained on the Bio-Rad VARIANT II Hb A1c method are tabulated below.

CONCLUSION

Peak characteristics, retention times, and percentage of hemoglobin variant may be used to establish the presence of a hemoglobin variant and to provide a tentative identification of some hemoglobin variants on the Bio-Rad VARIANT II Hb A1c method.

Between-Method Variation in Human Chorionic Gonadotropin Test Results

Background: Results on sera and calibrators vary 1.4- to 2.3-fold among commercial human chorionic gonadotropin (hCG) assays. The relative contributions of calibrators, standards, hCG charge isoforms, and major structural variants to this variation have not been quantified.

Methods: Purified hCG was separated by isoelectric focusing into four fractions with pI ranges of 3–4, 4–5, 5–6, and 6–7. These four fractions together with pure hCG, hyperglycosylated hCG, hCG β-subunit (hCGb), nicked hCG, and hCGb core fragment (hCGbcf) were tested in nine commonly used commercial serum assays for hCG. The compositions of pure hCG preparations, standards, and commercial hCG preparations were determined by immunoassay.

Results: The three pure hCG preparations and the four hCG charge isoforms each showed parallel responses in the nine commercial hCG assays. Although wide variations were found in the detection of hCG structural variants by the nine assays (range for hyperglycosylated hCG, 468-1544 IU/L; for hCGb, 3187-5535 IU/L; for nicked hCG, 2736-4240 IU/L; and for hCGbcf, &lt;2–130 IU/L), this did not correlate with the between-method variation observed in results for the three pure hCG preparations. Commercial preparations of hCG and calibrators showed great variation in their content of hCG structural variants (from 34% to 100% intact hCG).

Conclusions: Intermethod differences in hCG results were not explained by changes in responses attributable to hCG charge isoforms or to hCG structural variants, but wide variation was observed in concentrations of hCG structural variants in calibrators and in detection of these structural variants. Differences in assay specificity and in composition of the calibrators are the most likely sources of between-method variation.

Measurement of inaccuracy and imprecision of HCG methods using dilutions of the WHO 4th IS-HCG standard and a pregnant patient's serum

INTRODUCTION

Differences in human chorionic gonadotropin (hCG) results obtained by seven different methods were documented by analyzing dilutions of the WHO 4th International Standard (IS) and a pregnant patient's serum.

MATERIALS AND METHODS

Biases of +30.9 to -37.5% and +36.8 to -36.1% from the target concentration were found for the WHO 4th IS and patient sample dilutions, respectively.

RESULTS

Imprecision was calculated from replicate measurements of hCG on the different sample dilutions. Imprecision ranged from 1.0% to 18.9% and 1.1% to 5.3% for the WHO 4th IS and patient sample dilutions, respectively. Using a maximum allowable error of 12.5% for hCG measurements, we found that two instruments were so biased that their hCG measurements could not be interchanged with hCG values produced by any of the other systems.

DISCUSSION

It is ideal to use only one hCG methodology for the serial monitoring of hCG; otherwise, hCG methods should be carefully chosen to minimize inter-method bias.

Comparison of lactate, bilirubin and hemoglobin F concentrations obtained by the ABL 700 series blood gas analyzers with laboratory methods

OBJECTIVE

To compare lactate, bilirubin and Hemoglobin F concentrations obtained on ABL 700 series blood gas analyzers with those from laboratory methods.

DESIGN AND METHOD

Pooled neonatal plasma, cord blood and adult plasma samples were used for comparison of bilirubin, hemoglobin F and lactate concentrations respectively.

RESULTS

Results obtained on the ABL 700 series compared favorably (Deming regression slopes 0.97-1.13) with those from laboratory methods. For lactate ABL (y) = 1.13 Vitros (x) -0.43 with a CI (slope) of 1.10 to 1.16, CI (int) of -0.61 to -0.28. For hemoglobin F ABL(y) = 1.11 Variant (x) -8.0 with a CI (slope) of 0.88 to 1.33, CI (int) of -25.3 to 9.3. The three bilirubin comparisons are as follows: 1) Unistat (y) = 1.10 Vitros (x) -16.12 with CI (slope) of 1.06 to 1.14 and CI (int) of -25.3 to -6.9. 2), ABL (y) = 0.97 Vitros(x) -10.16 with CI (slope) of 0.94 to 1.00 and CI (int) of -17.6 to 2.73) Unistat (y) = 1.14 (x)-4.58 with CI (slope) of 1.09 to 1.18 and CI (int) of -13.6 to 4.5.

CONCLUSION

The ABL 700 series gave comparable results for lactate, bilirubin and hemoglobin F with laboratory methods and may be used in patient care.

Analytical evaluation of the Bio-Rad variant II automated HbA(1C) analyzer

OBJECTIVES

To evaluate the analytical performance of the Bio-Rad Variant II HbA(1C) analyzer (a completely automated system for the quantification of glycohemoglobin [HbA(1C)] in blood).

DESIGN AND METHODS

The analytical parameters of precision, linearity and analytical range were assessed and HbA(1C) results from the Variant II were compared to HbA(1C) results from the Bio-Rad Variant (a method certified by the National Glycohemoglobin Standardization Program). The effect of a variety of hemoglobin variants on HbA(1C) obtained on the system was investigated.

RESULTS

Total imprecision was less than 5% and the results compared well with those from an established method. The method has a wide analytical range with no carryover between specimens.

CONCLUSION

The HbA(1C) method on the Variant II gives acceptable analytical performance.

Laboratory investigation of hemoglobinopathies and thalassemias: review and update

Structural hemoglobin (Hb) variants typically are based on a point mutation in a globin gene that produce a single amino acid substitution in a globin chain. Although most are of limited clinical significance, a few important subtypes have been identified with some frequency. Homozygous Hb C and Hb S (sickle cell disease) produce significant clinical manifestations, whereas Hb E and Hb D homozygotes may be mildly symptomatic. Although heterozygotes for these variants are typically asymptomatic, diagnosis may be important for genetic counseling. Thalassemia, in contrast, results from quantitative reductions in globin chain synthesis. Those with diminished beta-globin chains are termed beta-thalassemias, whereas those with decreased alpha-chain production are called alpha-thalassemias. Severity of clinical manifestations in these disorders relates to the amount of globin chain produced and the stability of residual chains present in excess. The thalassemia minor syndromes are characterized clinically by mild anemia with persistent microcytosis. Thalassemia intermedia (i.e., Hb H disease) is typified by a moderate, variably compensated hemolytic anemia that may present with clinical symptoms during a period of physiologic stress such as infection, pregnancy, or surgery. The thalassemia major syndromes produce severe, life-threatening anemia. alpha-Thalassemia major usually is incompatible with extrauterine life; beta-thalassemia major presents in infancy and requires life-long transfusion therapy and/or bone marrow transplantation for successful control of the disease. Double heterozygosity for certain structural variants and/or thalassemia syndromes may also lead to severe clinical disease. Several guidelines have been published that outline the required steps for hemoglobinopathy and thalassemia investigation. The availability of HPLC has streamlined many of these requirements, allowing an efficient stepwise diagnostic strategy for these complex disorders.

Laboratory Investigation of Hemoglobinopathies and Thalassemias: Review and Update

Structural hemoglobin (Hb) variants typically are based on a point mutation in a globin gene that produce a single amino acid substitution in a globin chain. Although most are of limited clinical significance, a few important subtypes have been identified with some frequency. Homozygous Hb C and Hb S (sickle cell disease) produce significant clinical manifestations, whereas Hb E and Hb D homozygotes may be mildly symptomatic. Although heterozygotes for these variants are typically asymptomatic, diagnosis may be important for genetic counseling. Thalassemia, in contrast, results from quantitative reductions in globin chain synthesis. Those with diminished β-globin chains are termed β-thalassemias, whereas those with decreased α-chain production are called α-thalassemias. Severity of clinical manifestations in these disorders relates to the amount of globin chain produced and the stability of residual chains present in excess. The thalassemia minor syndromes are characterized clinically by mild anemia with persistent microcytosis. Thalassemia intermedia (i.e., Hb H disease) is typified by a moderate, variably compensated hemolytic anemia that may present with clinical symptoms during a period of physiologic stress such as infection, pregnancy, or surgery. The thalassemia major syndromes produce severe, life-threatening anemia. α-Thalassemia major usually is incompatible with extrauterine life; β-thalassemia major presents in infancy and requires life-long transfusion therapy and/or bone marrow transplantation for successful control of the disease. Double heterozygosity for certain structural variants and/or thalassemia syndromes may also lead to severe clinical disease. Several guidelines have been published that outline the required steps for hemoglobinopathy and thalassemia investigation. The availability of HPLC has streamlined many of these requirements, allowing an efficient stepwise diagnostic strategy for these complex disorders.

Comparison of hemoglobin A1C results by two different methods on patients with structural hemoglobin variants

OBJECTIVES

The objective was to compare hemoglobin A1C (HbA1C) results obtained by two methods based on different analytical principles for individuals with a structural hemoglobin variant.

DESIGN AND METHODS

Hemoglobin A1C results were obtained using the Bio-Rad Variant (based on cation exchange chromatography) and the Bayer DCA 2000 (based on an immunological reaction) on individuals with a structural hemoglobin variant. The identity of the hemoglobin variant was confirmed by high pressure liquid chromatography (HPLC) and electrophoresis.

RESULTS

Hemoglobin A1C results obtained by the two methods on individuals with S, C, D, and E trait were in close agreement.

CONCLUSION

The Bio-Rad Variant and Bayer DCA 2000 produce equivalent hemoglobin A1C results on patients with S, C, and E trait. With appropriate correction, correlation of hemoglobin A1C results from the Bio-Rad Variant for individuals with D trait was good (r = 0.927). Glycohemoglobin results obtained by the two methods for some unusual structural hemoglobin variants were in close agreement.

Enzyme immunoassay of valproic acid using the Abbott ABA-200 analyzer

The enzyme immunoassay of valproic acid using EMIT reagents was developed for an Abbott ABA-200 analyzer. The number of tests per package that could be obtained using this method was at least three times that suggested by the reagent manufacturer. The reproducibility of the method was assessed by within-run and day-to-day reproducibility studies and the accuracy of the method was assessed by comparison of results obtained to those obtained using a gas-chromatographic method and by performance on an inter-laboratory therapeutic drug monitoring quality control programme.