New HPLC instrument performance evaluation in HbA1c determination and comparison with capillary electrophoresis.

Glycated hemoglobin (HbA1c) measurement provides the most important medium to long-term marker of time-averaged glycemic status. Its relationship to clinical outcome in diabetes has been convincingly demonstrated for both type 1 and type 2 diabetes. The main HbA1c measurement methods for clinical routine are as follows: ion-exchange chromatography; affinity chromatography, capillary electrophoresis, immunoassay and enzymatic methods. In this study, we evaluated the analytical performances of a new HPLC instrument (Tosoh HLC-723 G11 in the VAR mode) in HbA1c analysis and compared it with a capillary electrophoresis instrument (Sebia Capillarys 2 Flex Piercing). HbA1c analysis was performed in parallel by both methods for 250 samples randomly chosen from healthy and diabetic subjects at 'Tor Vergata' University Hospital of Rome. Tosoh HLC-723 G11 showed good reproducibility for 10 days both in quality controls and in samples analyzed (%CV < 2%). We found good linearity for HbA1c values ranging from 15 mmol/mol (3.5%) to 178 mmol/mol (18.5%), with a correlation coefficient R2 = 1. In a comparison between Tosoh HLC-723 G11 and Capillarys 2FP a good correlation (r = 0.99) was found; however, Tosoh HLC-723 G11 showed higher values in the low range of HbA1c and lower in the high range (Tosoh HLC-723 G11 = 4.3043 + 0.913 Capillarys 2FP; p < 0.001). Tosoh HLC-723 G11 showed good repeatability, reproducibility, accuracy and automated simplicity, and it seemed suitable for routine use in clinical chemistry laboratories.

Comparison of glycation degrees of HbG-Coushatta and HbG-Taipei with HbA using liquid chromatography with tandem mass spectrometry.

BACKGROUND: Hemoglobin A1c(HbA1c) is widely used to measure glycemic status and control in diabetes testing and treatment and is an important risk factor forcomplications of diabetes. Hemoglobin variants can interfere with the HbA1c testing method by reducing the life span of erythrocytes or due to differences in glycation degrees. In this study, glycation levels of the HbA, HbG-Coushatta, and HbG-Taipei ß-chains (ßA, ßG-Coushatta, and ßG-Taipei, respectively) were examined. METHODS: Blood samples from heterozygotic patients (HbG-Coushatta/HbA, HbG-Taipei/HbA) were analyzed. Glycation rateswere determined using high-performance liquid chromatography with tandem mass spectrometry. Ratios of glycated ßG-Coushatta to glycated ßA and glycated ßG-Taipei to glycated ßA were calculated by comparingareas under the curves from extracted ion chromatograms. RESULTS: ßG-Coushatta and ßG-Taipei were 6.08 ± 1.38% and 5.95 ± 0.93% glycated (respectively), which were significantly higher than ßA chains(4.55 ± 1.30% and 4.51 ± 0.91%, respectively; p = 0.000). The total glycation degree (α + ß) in HbG-Coushatta and HbG-Taipei heterozygotes were estimated to be 9% and 8% higher than those of HbA homozygotes (P＜0.001), respectively. CONCLUSION: ßG-Coushatta and ßG-Taipei glycation degrees were significantly higher than ßA, while the differences in total hemoglobin (α + ß) were small and unlikely to impact the clinical interpretation of HbA1c results.

Quantitation of Inositol Phosphates by HPLC-ESI-MS.

The coupling of anion exchange high-pressure liquid chromatography (HPLC) with electrospray ionization mass spectrometry (ESI-MS) allows for the simultaneous detection of the six forms of inositol phosphate (InsP). Here we describe a rapid quantitative analysis of InsPs by HPLC-ESI-MS, which can be applied to a wide array of sample types. With this method, InsPs could be separated and detected within 20 min of sample injection. The detection limit was as low as 25 pmol (i.e., ca. 2 nmol/g sample) for each type of InsP, which is particularly important for analytes that are often present at low abundance in nature.

Recognition of rare hemoglobin variants by hemoglobin A1c measurement procedures.

BACKGROUND: Unrecognized hemoglobinopathies can lead to measured hemoglobin A1c (Hb A1c) concentrations that are erroneous or misleading. We determined the effects of rare hemoglobin variants on capillary electrophoresis (CE) and HPLC methods for measurement of Hb A1c. METHODS: We prospectively investigated samples in which Hb A1c was measured by CE during a 14-month period. For samples in which the electropherograms suggested the presence of rare hemoglobinopathies, hemoglobin variants were identified by molecular analysis or by comparison with electropherograms of known variants. When sample volume permitted, Hb A1c was measured by 2 HPLC measurement procedures and by boronate affinity HPLC. RESULTS: Hb A1c was measured by CE in 33,859 samples from 26,850 patients. 15 patients (0.06%) were identified as having rare hemoglobinopathies: Hbs A2 prime, Agenogi, Fannin-Lubbock I, G Philadelphia, G San Jose, J Baltimore, La Desirade, N Baltimore, Nouakchott, and Roanne. Among 6 of these samples tested by 2 ion-exchange HPLC methods, the rare Hb was detected by both HPLC methods in only one sample, and none were detected by boronate affinity HPLC. The mean of the Hb A1c results of 2 HPLC methods differed from the result of the CE method by 0.7-2.2% Hb A1c in samples with variant hemoglobins versus <0.2% Hb A1c in samples without variants. CONCLUSION: Measurement procedures differ in the ability to detect the presence of rare Hb variants and to quantify Hb A1c in patients who harbor such variants.

Quantification of inositol phosphates in almond meal and almond brown skins by HPLC/ESI/MS.

The extraction and measurement of all six forms of inositol phosphates (InsPs) in almond meal and brown skins were improved from existing methods by pH adjustment, supplementation of EDTA, and rapid analysis via anion-exchange high-performance liquid chromatography coupled with electrospray ionization mass spectrometry. The quantity of InsPs in six major almond cultivars ranged from 8 to 12µmol/g in the meal and 5 to 14µmol/g in the brown skins. InsP6 was the dominant form, but lower forms still accounted for ∼20% of the total InsPs molar concentration in a majority of the samples. InsPs contributed 32-55% of the organic phosphorus content and 20-38% of the total phosphorus content in the meal. In brown skins, these ranges were 44-77% and 30-52%, respectively. The successful application of this analytical method with almonds demonstrates its potential use for re-examination of the reported phytic acid contents in many other tree nuts, legumes, grains, and complex foods.

Development of a dose assay for a Clostridium difficile vaccine using a tandem ion exchange high performance liquid chromatography method.

Clostridium difficile is a gram-positive intestine bacterium that causes a severe diarrhea and could eventually be lethal. The main virulence factor is related to the release of two major exotoxins, toxin A (TcdA) and toxin B (TcdB). Recent C. difficile-associated disease (CDAD) outbreaks have been caused by hypervirulent strains which secrete an additional binary toxin (CDTa/CDTb). Vaccination against these toxins is considered the best way to combat the CDAD. Recently, a novel tetravalent C. difficile vaccine candidate containing all four toxins produced from a baculovirus expression system has been developed. A dose assay to release this tetravalent C. difficile vaccine was developed using tandem ion-exchange HPLC chromatography. A sequential weak cation exchange (carboxyl group) and weak anion exchange (tertiary amine group) columns were employed. The four C. difficile vaccine antigen pIs range from 4.4 to 8.6. The final optimized separation employs salt gradient elution at two different pHs. The standard analytical parameters such as LOD, LOQ, linearity, accuracy, precision and repeatability were evaluated for this method and it was deemed acceptable as a quantitative assay for vaccine release. Furthermore, the developed method was utilized for monitoring the stability of the tetravalent C. difficile vaccine in final container.

Hb Cervantes, Hb Marañón, Hb La Mancha and Hb Goya: Description of 4 new haemoglobinopathies.

OBJECTIVES: α-thalassemias are caused by a deficiency in or absence of synthesis of the α-chain of haemoglobin (Hb). In contrast, structural haemoglobinopathies are due to mutations that change the amino acid sequence of the protein chain. We report 4 newly identified α-chain Hb variants. Two variants were hyper-unstable, whereas the other 2 were structural variants with an altered electrophoretic mobility. DESIGN AND METHODS: The first 2 families were identified because of microcytosis and hypochromia with a normal Hb A2 and Hb F but without iron deficiency. The other 2 families came to scrutiny because of a peak of abnormal Hb during routine analytical assays. These Hb variants were characterized by specific sequencing. RESULTS: The hyper-instability of Hb Cervantes is probably due to its lower affinity for the alpha chain haemoglobin-stabilizing protein (AHSP). Hb Marañón is another unstable Hb variant that produces an α-thalassemia phenotype. For the identification of Hb La Mancha, a molecular characterization by sequencing was required. Finally, Hb Goya was found to have the same electrophoretic mobility as Hb J. A lower percentage of the variant was obtained due to a possible component of instability, though the patient did not show evidence of anaemia. CONCLUSION: These variants of Hb add to the variety and complexity of disorders of the genes that encode Hb.