Glycated Hemoglobin Measurement: Comparison of Three Methods Versus High Performance Liquid Chromatography.

BACKGROUND: HbA1c result provide information on metabolic control in diabetes mellitus (DM) and could also be used for its diagnosis. For its determination, the laboratory must be certified by the National Glycohemoglobin Standardization Program (NGSP) or the International Federation of Clinical Chemistry (IFCC) and comply with a strict quality control program. AIMS: To determine the correlation and agreement between HbA1c results measured by three analytical methods (enzymatic, turbidimetric, and capillary electrophoresis) versus HPLC. METHODS: Method comparison-1245 samples from equal number of subjects at 45 Association of High Complexity Laboratories (Asociación de Laboratorios de Alta Complejidad-ALAC) centers, centralizing sample processing and operator. Statistical analysis-analysis of variance (ANOVA) and nonparametric Friedman ANOVA test for related samples, means, and medians. Correlation and concordance-Pearson's correlation and linear regression, intraclass correlation coefficient (Passing and Bablock and Bland and Altman). RESULTS: The comparison of mean values obtained by the four methods showed statistically significant, but clinically irrelevant, differences: HbA1c by HPLC versus Electrophoresis 0.06% (0.42 mmol/mol) P = .000 (± 1.96 DS -0.070 -0.047), Enzymatic 0.087% (1 mmol/mol) P = .000 (± 1.96 DS 0.077 0.098), Turbidimetric 0.056% (0.38 mmol/mol) P = 0.000 (± 1.96 DS -0.067 -0.044). Their concordance showed intraclass correlation of single measures of 0.982 P < .001 (95% CI 0.987 - 0.9838). CONCLUSIONS: The three methods present low variability and high correlation versus the HPLC.

A missense mutation in the extracellular domain of Fas: the most common change in Argentinean patients with autoimmune lymphoproliferative syndrome represents a founder effect.

UNLABELLED: Mutations in the Fas gene (TNFRSF6) are the most common causes of Autoimmune Lymphoproliferative Syndrome (ALPS-FAS). PURPOSE: In Argentina almost a third of patients with ALPS-FAS present a missense mutation affecting the extracellular cysteine rich domain 2 of Fas, p.Cys107Tyr (C107Y). This change was found in homozygous state in 2 patients from a consanguineous family, and heterozygously, in 3 other patients from 3 unrelated families. In these families, 12 relatives were identified as healthy carriers of the mutation. We sought to test the hypothesis that this mutation actually represents a single haplotype of TNFRSF6. METHODS: DNAs from ALPS-C107Y patients and their families, as well as from 150 Argentinean control subjects were sequenced for the known higher frequency single nucleotide polymorphisms (SNPs) of TNFRSF6. The C107Y-carriers were also genotyped at 5 microsatellites proximal to the Fas gene locus. RESULTS: All C107Y alleles presented a unique intragenic haplotype that could be restricted to this group. Extent of haplotype sharing and variability of microsatellite alleles in C107Y chromosomes support the presence of a single haplotype block including the mutation and encompassing 2.395 Mb. CONCLUSIONS: A founder effect for C107Y has been evidenced in this work and the most common recent ancestor to the patients probably lived 350 years ago. This constitutes the first report of a founder event in ALPS.