Ischemia modified albumin as a marker of hypoxia in preterm infants in the first week after birth.

BACKGROUND: Tissue hypoxia remains a leading cause of morbidity and mortality in preterm infants. Current biomarkers often detect irreversible hypoxic cellular injury (i.e. lactate) and are non-specific. A new biomarker is needed which detects tissue hypoxia before irreversible damage occurs. AIMS: To investigate the relation between serum ischemia modified albumin (IMA), a marker of hypoxia; and analytic variables, patient related variables and conditions associated with hypoxia, in preterm infants. STUDY DESIGN: Retrospective cohort study. SUBJECTS: Infants with a gestational age < 30 weeks and/or birth weight < 1000 g. OUTCOME MEASURES: We collected two remnant blood samples in the first week after birth and measured IMA. IMA/albumin ratio (IMAR) was used to adjust for albumin. We assessed correlations between IMA(R) and analytic variables (albumin, lipemia- and haemolysis index); mean-2 h SpO2; mean-2 h variability of regional splanchnic oxygen saturation (rsSO2), measured using near-infrared spectroscopy; and patent ductus arteriosus (PDA). RESULTS: Sixty-five infants were included. Albumin, the lipemia- and haemolysis index correlated negatively with IMA (r:-0.620, P<0.001; r:-0.458, P<0.001; and r:-0.337, P=0.002). IMAR correlated negatively with SpO2 (rho:-0.614, P<0.001). Lower rsSO2 variability correlated with higher IMAR values (rho:-0.785, n=14, P=0.001 and rho:-0.773, n=11, P=0.005). Infants with a hemodynamic significant PDA (hsPDA) had higher IMAR values than infants without PDA (0.13 [0.11-0.28], n=16 vs. 0.11 [0.08-0.20], n=29, P=0.005 and 0.11 [0.09-0.18], n=13 vs. 0.09 [0.06-0.17], n=37, P=0.026). CONCLUSIONS: When adjusted for albumin, the lipemia- and haemolysis index, IMAR has potential value as a marker for systemic hypoxia in preterm infants, considering the associations with SpO2, variability of rsSO2, and hsPDA.

Influence of Storage and Inter- and Intra-Assay Variability on the Measurement of Inflammatory Biomarkers in Population-Based Biobanking.

BACKGROUND: In the present study, we examined the effect of sample storage on the reproducibility of several inflammatory biomarkers, including high-sensitivity C-reactive protein (hsCRP), high-sensitivity interleukin-6 (hsIL6), and high-sensitivity tumor necrosis factor alpha (hsTNFα). In addition, we assessed inter- and intra-assay variability between collaborating biobanks. METHODS: In total, 240 fasting plasma samples were obtained from the LifeLines biobank. Samples had been stored for less than 2 or more than 4 years at -80°C. Measurements were performed at three different laboratories. hsCRP was measured by immunonephelometry and ELISA, hsIL6, and hsTNFα samples were measured with ELISAs from two different manufacturers. For confirmation, similar analyses were performed on samples obtained from a subpopulation of 80 obese individuals. Passing-Bablok regression analysis and Bland-Altman plots were used to compare the results. RESULTS: We observed good stability of samples stored at -80°C. hsCRP measured on the day of blood draw was similar to levels measured after more than 4 years of storage. There were small interlaboratory differences with the R&D ELISAs for hsIL6 and hsTNFα. We found a linear correlation between the Bender Medsystems ELISA and the R&D ELISA for hsIL6, with significantly higher levels measured with the R&D ELISA. Over 90% of hsTNFα samples measured with the IBL ELISA were below the detection limit of 0.13 ng/L, rendering this assay unsuitable for large-scale analysis. Similar results were found in the confirmation study. CONCLUSION: In summary, plasma hsCRP showed good stability in samples stored for either less than 2 years or more than 4 years at -80°C. Both the R&D and Bender Medsystems for hsIL6 measurement yielded similar results. The IBL hsTNFα assay is not suited for use in biobanking samples. Assays for the measurement of inflammatory biomarker assays should be rigorously tested before large sample sets are measured.

Reference values for aldosterone-renin ratios in normotensive individuals and effect of changes in dietary sodium consumption.

BACKGROUND: Determination of the aldosterone-to-renin ratio (ARR) in blood is the preferred screening test for primary aldosteronism. Renin can be measured as the plasma renin activity (PRA) or the plasma renin concentration (PRC). Consequently, the ARR can be measured either based on the PRA (ARR(pra)) or based on the PRC (ARR(prc)). In contrast with the ARR(pra), the data on reference values for the ARR(prc) are limited. Moreover, whether the ARR(pra) or ARR(prc) is affected by variations in salt intake is unknown. METHODS: We measured the PRA, the PRC, and serum aldosterone in 100 normotensive individuals between 20 and 70 years of age before and after a 3-day oral sodium-loading test (SLT). Participants were stratified according to age and sex. Data are presented as the median and interquartile range (IQR). RESULTS: Urinary sodium excretion after the SLT was ≥200 mmol/24 h in all participants. Serum aldosterone, PRA, and PRC values were significantly reduced after the SLT. PRC and PRA results were highly correlated [Spearman rank correlation r(s) = 0.80 and 0.74 before and after SLT, respectively; P < 0.001 for both]. The central 95% reference intervals for ARR(pra) before and after SLT were 0.07-1.45 h(-1) and 0.06-1.84 h(-1), respectively. The corresponding reference intervals for ARR(prc) were 4.1-81.3 pmol/ng and 3.9-74.8 pmol/ng. The median ARR(prc) decreased after the SLT from 19.5 pmol/ng (IQR, 13.0-29.4 pmol/ng) to 18.6 pmol/ng (IQR, 9.4-27.1 pmol/ng) (P = 0.005), whereas the median ARR(pra) did not change (P = 0.12). Both the ARR(prc) and ARR(pra) at baseline were higher in women than in men, whereas no sex difference was observed after sodium loading. CONCLUSIONS: We present reference values for the ARR(prc) for healthy individuals. The ARR is affected to a variable degree by sex and sodium intake.

Salt loading affects cortisol metabolism in normotensive subjects: relationships with salt sensitivity.

We studied cortisol metabolism together with insulin sensitivity [homeostatic model assessment (HOMA)] and renal hemodynamics in 19 salt-resistant (sr) and nine salt-sensitive (ss) normotensive subjects after a low- and high-salt diet. Results are described as high- vs. low-salt diet. Sum of urinary cortisol metabolite excretion (sum(metabolites)) increased in sr subjects (3.8 +/- 1.6 vs. 3.1 +/- 1.1 microg/min per square meter, P < 0.05) and decreased in ss subjects (2.3 +/- 1.0 vs. 2.9 +/- 1.1 microg/min per square meter, P < 0.05). Plasma 0830 h cortisol decreased in sr subjects but did not change significantly in ss subjects. In all subjects, the absolute blood pressure change correlated negatively with the percentage change in sum(metabolites) (P < 0.05) and positively with the percentage change in renal vascular resistance (P < 0.05). Sum(metabolites) during high-salt diet correlated negatively with the percentage changes in plasma 0830 h cortisol (P < 0.05) and renal vascular resistance (P = 0.05). HOMA did not change in either group, but the percentage change in HOMA correlated positively with the percentage change in plasma cortisol (P = 0.001) and negatively with the percentage change in sum(metabolites) (P < 0.01). Parameters of 11 beta-hydroxysteroid dehydrogenase activity were not different between groups and did not change. In conclusion, these data suggest that cortisol elimination is affected differently after salt loading in sr and ss subjects. Changes in circulating cortisol might contribute to individual sodium-induced alterations in insulin sensitivity.