Hipoglucemia de causa autoinmune por anticuerpos anti-insulina / Autoimmune hypoglycemia due to anti-insulin antibodies

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Overestimation of Albumin Measured by Bromocresol Green vs Bromocresol Purple Method: Influence of Acute-Phase Globulins.

BACKGROUND: Usually serum albumin is measured with dye-binding assay as bromocresol green (BCG) and bromocresol purple (BCP) methods. The aim of this paper was to examine the differences in albumin measurements between the Advia2400 BCG method (AlbBCG), Dimension RxL BCP (AlbBCP) and capillary zone electrophoresis (CZE). METHODS: Albumin concentrations from 165 serum samples were analysed using AlbBCG, AlbBCP and CZE. CZE was employed to estimate different serum protein fractions. Influence of globulins on albumin concentration discrepancies between methods was estimated as well as the impact of the albumin method on aCa concentrations. Medcalc was employed for statistical analysis, setting a value of P < 0.05 as significant. RESULTS: Correlation of AlbBCG and AlbBCP was r = 0.948 (p < 0.0001), but mean difference was large. Bland-Altman plots showed greater bias at lower albumin concentrations. AlbBCG were positively biased versus CZE (3.54 g/L). There was good agreement between CZE and ALbBCP (< 1 g/L). The AlbBCG assay bias shows a good correlation with alpha-1-globulin concentrations (r = 0.758); moderate and weak correlations were observed with CRP (r = 0.729) and alpha-2-globulin (r = 0.585); we found no correlation with beta-globulin (r = 0.120) or gamma-globulin (r = -0.303). Mean aCa based on AlbBCG and AlbBCP methods were 2.34 ± 0.15 mmol/L and 2.46 ± 0.16 mmol/L (p < 0.01), with a mean BCG-BCP difference of -0.12. CONCLUSION: Albumin results from the BCP and BCG methods may result in unacceptable differences and clinical confusion, especially at lower albumin concentrations. Serum acute phase proteins contribute to overestimating the albumin concentration using AlbBCG.

Recursos y fuentes de infomación útiles en la práctica de la medicina de laboratorio basado en la evidencia / Resources and sources useful in evidence-based laboratory medicine practice

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Cell-free DNA as a noninvasive acute rejection marker in renal transplantation.

BACKGROUND: Acute rejection (AR) is a key conditioning factor for long-term graft function and survival in renal transplantation patients. The standard care with creatinine measurements and biopsy upon allograft dysfunction implies that AR is usually detected at advanced stages. Rapid noninvasive biomarkers of rejection are needed to improve the management of these patients. We assessed whether total cell-free DNA (tCF-DNA) and donor-derived cell-free DNA (ddCF-DNA) were useful markers for this purpose, both in plasma and in urine. METHODS: Plasma and urine samples from 100 renal transplant recipients were obtained during the first 3 months after transplantation. tCF-DNA and ddCF-DNA were analyzed by quantitative PCR for the HBB (hemoglobin, beta) and the TSPY1 (testis specific protein, Y-linked 1) genes, respectively. We observed 19 episodes of AR, as well as other complications, such as acute tubular necrosis, nephrotoxicity, and infections. RESULTS: Plasma tCF-DNA concentrations increased markedly during AR episodes, often before clinical diagnosis, and returned to reference values after antirejection treatment. A cutoff plasma tCF-DNA concentration of 12 000 genome equivalents/mL correctly classified AR and non-AR episodes in 86% of posttransplantation complications (diagnostic sensitivity, 89%; specificity, 85%). Although similar increases were observed during severe posttransplantation infections, use of the combination of plasma tCF-DNA and procalcitonin (PCT), a specific marker of sepsis, significantly improved the diagnostic specificity (to 98%; 95% CI, 92%-100%), with 97% of the episodes being correctly classified. Use of transrenal DNA and ddCF-DNA concentrations did not add relevant information. CONCLUSIONS: Given that renal biopsy is the gold standard for detecting AR, analysis of both plasma tCF-DNA and PCT could permit a more selective use of this invasive procedure.

Elevated transrenal DNA (cell-free urine DNA) in patients with urinary tract infection compared to healthy controls.

OBJECTIVE: To study whether levels of transrenal DNA (Tr-DNA) are influenced by the presence of urinary tract infections (UTI). METHODS: Tr-DNA concentrations were measured in 124 donors and 55 patients with UTI. Two methods for DNA extraction were compared. RESULTS: UTI patients showed higher concentrations than the donors (normal range: 0-147 GE/mL). QIAamp MiniElute Virus Spin Kit was more efficient than QIAamp DNA Blood Mini Kit. CONCLUSION: Increased concentrations of Tr-DNA urine DNA are shown in presence of UTI.

Increase in and clearance of cell-free plasma DNA in hemodialysis quantified by real-time PCR.

BACKGROUND: Recently cell-free plasma DNA has been described as a marker of apoptosis during hemodialysis (HD), but little is known about how different dialysis membranes may contribute to this process or whether pre-HD levels are restored afterwards. Here we evaluate the influence of the dialysis membrane on cell-free plasma DNA levels and investigate the clearance of plasma circulating DNA after HD. METHODS: Cell-free plasma DNA was measured using a real-time quantitative PCR for the beta-globin gene. Reference values for plasma DNA were established in a group of 100 healthy voluntary blood donors. Pre- and post-HD levels were also measured in 30 patients with end-stage renal disease on regular HD (52 sessions; 104 samples). The sessions lasted for 2.5-5 h. Different dialysis membranes were compared: high-flux (n=37) vs. low-flux (n=15) and polysulfone (n=42) vs. modified cellulose (n=10). To determine the time at which pre-HD levels are restored, DNA was quantified in serial plasma samples obtained from 10 of these 30 patients, just before and immediately after HD, as well as at 30, 60 and 120 min after HD. RESULTS: Reference plasma DNA values for healthy blood donors ranged from 112 to 2452 gEq/mL (median 740 gEq/mL). Cell-free plasma DNA levels significantly increased during HD (Wilcoxon test for paired samples, p<0.0001), with increases of more than four-fold observed in 75% of the patients after HD. There was no significant linear association between the length of the HD session (between 2.5 and 5 h) and the increase in cell-free plasma DNA concentration (Pearson correlation). No significant differences were observed between different types of membranes (Mann-Whitney U-test). Plasma DNA returned to pre-HD levels by 30 min after HD, regardless of the starting concentration. CONCLUSIONS: Plasma DNA levels significantly increase after a conventional 2.5-5-h HD session. Therefore, HD patients require special consideration for correct interpretation of plasma DNA concentrations. This parameter can be considered a reliable diagnostic tool for certain pathologies when measured at least 30 min after a HD session without further complications. The different dialysis membranes used in this study had no influence on cell-free plasma DNA concentrations, so the level of circulating DNA is not an appropriate marker of dialysis membrane biocompatibility.

Single-nucleotide polymorphisms in the promoter region of the PARKIN gene and Parkinson's disease.

Mutations in the PARKIN gene have been identified in families with recessively inherited Parkinson disease (PD). Common DNA-polymorphisms at the PARKIN gene could contribute to the risk for PD in the general population. Here we searched for DNA-polymorphisms in the PARKIN promoter. We found two single nucleotide polymorphisms (-324 A/G and -797 A/G). In order to analyse the association of PD with these and two previously described polymorphisms (1281 G/A, Asp394Asn, and 601 G/A, Ser167Asn) we genotyped 105 patients and 150 healthy controls. Allele and genotype frequencies for the four polymorphisms did not differ between patients and controls, or between patients with an early-onset (< or =40 years; n = 20) and a late-onset (>40 years; n = 85). According to our data, the genetic variation at the PARKIN gene (including promoter polymorphisms) did not contribute to the risk of developing PD in the general population.