The complexity of kidney disease and diagnosing it - cystatin C, selective glomerular hypofiltration syndromes and proteome regulation

Estimation of kidney function is often part of daily clinical practice, mostly done by using the endogenous glomerular filtration rate (GFR)-markers creatinine or cystatin C. A recommendation to use both markers in parallel in 2010 has resulted in new knowledge concerning the pathophysiology of kidney disorders by the identification of a new set of kidney disorders, selective glomerular hypofiltration syndromes. These syndromes, connected to strong increases in mortality and morbidity, are characterized by a selective reduction in the glomerular filtration of 5-30 kDa molecules, such as cystatin C, compared to the filtration of small molecules <1 kDa dominating the glomerular filtrate, for example water, urea and creatinine. At least two types of such disorders, shrunken or elongated pore syndrome, are possible according to the pore model for glomerular filtration. Selective glomerular hypofiltration syndromes are prevalent in investigated populations, and patients with these syndromes often display normal measured GFR or creatinine-based GFR-estimates. The syndromes are characterized by proteomic changes promoting the development of atherosclerosis, indicating antibodies and specific receptor-blocking substances as possible new treatment modalities. Presently, the KDIGO guidelines for diagnosing kidney disorders do not recommend cystatin C as a general marker of kidney function and will therefore not allow the identification of a considerable number of patients with selective glomerular hypofiltration syndromes. Furthermore, as cystatin C is uninfluenced by muscle mass, diet or variations in tubular secretion and cystatin C-based GFR-estimation equations do not require controversial race or sex terms, it is obvious that cystatin C should be a part of future KDIGO guidelines.

Strong Associations Between Early Tubular Damage and Urinary Cytokine, Chemokine, and Growth Factor Levels in Elderly Males and Females

Acute tubular necrosis is associated with high mortality rates and it is important to develop new biomarkers for tubular damage. The aim of this study was to investigate the effect of early tubular damage on a large number of urinary cytokines, chemokines, and growth factors. We selected 90 urine samples from the Prospective Investigation of the Vasculature in Uppsala Seniors Study (41 males and 49 females). The tubular damage markers cystatin C, neutrophil gelatinase-associated lipocalin (NGAL), and kidney injury molecule-1 (KIM-1) were analyzed in the urine samples and urinary cytokine levels were analyzed with 2 multiplex assays (proximity extension assay). After adjustment for sex, body mass index, estimated glomerular filtration rate, smoking, and multiplicity testing using the false discovery rate approach, there remained 26 cytokines that correlated significantly with urine cystatin C, 27 cytokines that correlated with NGAL, and 66 cytokines that correlated with KIM-1. Tubular damage shows a strong association with urinary cytokines, chemokines, and growth factors. Our findings indicate that multiplex proteomics could be a promising new approach to explore the complex effects of tubular damage.

Strong Associations between Plasma Osteopontin and Several Inflammatory Chemokines, Cytokines, and Growth Factors

Osteopontin is a member of the proinflammatory cytokine network, a complex system that involves many chemokines, cytokines, and growth factors. The aim of the present study was to study the associations between osteopontin and a large number of chemokines, cytokines, and growth factors. We analyzed plasma and urine osteopontin in 652 men from the Uppsala Longitudinal Study of Adult Men (ULSAM) study cohort and compared the levels with the levels of eighty-five chemokines, cytokines, and growth factors. We found significant associations between plasma osteopontin and 37 plasma biomarkers in a model adjusted for age, and 28 of those plasma biomarkers were significant in a model also adjusting for cardiovascular risk factors. There were no significant associations after Bonferroni adjustment between urine osteopontin and any of the studied plasma cytokine biomarkers. This study shows that circulating osteopontin participates in a protein–protein interaction network of chemokines, cytokines, and growth factors. The network contains responses, pathways, and receptor binding interactions relating to cytokines, regulation of the immune system, and also regulation of apoptosis and intracellular signal transduction.

Addition of cystatin C predicts cardiovascular death better than creatinine in intensive care

Objective

Decreased kidney function increases cardiovascular risk and predicts poor survival. Estimated glomerular filtration rate (eGFR) by creatinine may theoretically be less accurate in the critically ill. This observational study compares long-term cardiovascular mortality risk by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation; Caucasian, Asian, paediatric and adult cohort (CAPA) cystatin C equation and the CKD-EPI combined creatinine/cystatin C equation.

Methods

The nationwide study includes 22 488 intensive care patients in Uppsala, Karolinska and Lund University Hospitals, Sweden, between 2004 and 2015. Creatinine and cystatin C were analysed with accredited methods at admission. Reclassification and model discrimination with C-statistics was used to compare creatinine and cystatin C for cardiovascular mortality prediction.

Results

During 5 years of follow-up, 2960 (13 %) of the patients died of cardiovascular causes. Reduced eGFR was significantly associated with cardiovascular death by all eGFR equations in Cox regression models. In each creatinine-based GFR category, 17%, 19% and 31% reclassified to a lower GFR category by cystatin C. These patients had significantly higher cardiovascular mortality risk, adjusted HR (95% CI), 1.55 (1.38 to 1.74), 1.76 (1.53 to 2.03) and 1.44 (1.11 to 1.86), respectively, compared with patients not reclassified. Harrell’s C-statistic for cardiovascular death for cystatin C, alone or combined with creatinine, was 0.73, significantly higher than for creatinine (0.71), p<0.001.

Conclusions

A single cystatin C at admission to the intensive care unit added significant predictive value to creatinine for long-term cardiovascular death risk assessment. Cystatin C, alone or in combination with creatinine, should be used for estimating GFR for long-term risk prediction in critically ill.

Cystatin C predicts long term mortality better than creatinine in a nationwide study of intensive care patients

Decreased glomerular filtration rate (GFR) is linked to poor survival. The predictive value of creatinine estimated GFR (eGFR) and cystatin C eGFR in critically ill patients may differ substantially, but has been less studied. This study compares long-term mortality risk prediction by eGFR using a creatinine equation (CKD-EPI), a cystatin C equation (CAPA) and a combined creatinine/cystatin C equation (CKD-EPI), in 22,488 patients treated in intensive care at three University Hospitals in Sweden, between 2004 and 2015. Patients were analysed for both creatinine and cystatin C on the same blood sample tube at admission, using accredited laboratory methods. During follow-up (median 5.1 years) 8401 (37%) patients died. Reduced eGFR was significantly associated with death by all eGFR-equations in Cox regression models. However, patients reclassified to a lower GFR-category by using the cystatin C-based equation, as compared to the creatinine-based equation, had significantly higher mortality risk compared to the referent patients not reclassified. The cystatin C equation increased C-statistics for death prediction (p < 0.001 vs. creatinine, p = 0.013 vs. combined equation). In conclusion, this data favours the sole cystatin C equation rather than the creatinine or combined equations when estimating GFR for risk prediction purposes in critically ill patients.

Day-to-day variation of the kidney proximal tubular injury markers urinary cystatin C, KIM1, and NGAL in patients with chronic kidney disease

Background: It is important to know the intraindividual variation of biomarkers to be able to distinguish a change of a biomarker due to the course of the disease from the normal biological variation of the marker. The purpose of this study was to investigate the day-to-day variability of urine markers in nephrology patients.Materials: 23 nephrology patients were included in the study. First morning urine samples were collected daily for ten consecutive days and analyzed for U-cystatin C, U-KIM1, U-NGAL and U-creatinine. The day-to-day variation was calculated as concentrations of the markers and as creatinine ratios. Values deviating more than the 90^th percentile of the normal intraindividual variation was used to define a disease/treatment specific change.Results: The day-to-day coefficient of variation (CV) for individual patients varied between 9.6 and 100.3% for NGAL (mean 45.6%) and between 8.8 and 107.3% for the NGAL/creatinine ratio (mean 43.8%). The corresponding values for KIM1 were between 10.9 and 60.2% (mean 30.1%) and for the ratio between 8.7 and 59.8% (mean 23.4%) and for cystatin C 3.8-67.4% (mean 25.0%) and for the cystatin C/creatinine ratio 5.9-78.4% (mean 24.8%).Conclusions: The similar intraindividual CV values between the renal tubules damage markers and their corresponding creatinine ratios speaks against using creatinine ratio. Using the 90^th percentiles of the CV values as a limit for clinical change means that NGAL has to change by 83.3%, KIM1 by 45.5% and Cystatin C by 46.3% before the change can be considered clinically significant in patients with chronic kidney disease.

Reference Intervals for Fecal Calprotectin in Pregnant Women Using a Particle Enhanced Turbidimetric Assay

BACKGROUND

Fecal calprotectin is widely used as a marker for inflammatory bowel diseases (IBD). IBD often affects women during their reproductive years, but there are no established reference intervals during pregnancy. The aim of the present study was to define reference values during pregnancy and in the postpartum period to allow comparisons between patient results and reference values.

METHODS

Fecal samples were collected from 84 healthy females during pregnancy week 26 to 28 and a second sample was collected six months after delivery. The samples were weighed, extracted, and centrifugated to remove debris. The extracted samples were then analyzed on a chemistry analyzer using a particle enhanced turbidimetric immunoassay reagent.

RESULTS

The calculated reference interval during pregnancy was < 127 μg/g (90% confidence interval, 90 - 164 μg/g) and the corresponding reference interval during the postpartum period was < 143 μg/g (60 - 226 μg/g). There were no significant statistical differences between F-calprotectin values analyzed at the two sampling times.

CONCLUSIONS

The reference values are slightly higher than the cutoff values of 50 - 100 μg/g often used as General cutoff for fecal calprotectin.

Associations Between Apolipoprotein A1, High-Density Lipoprotein Cholesterol, and Urinary Cytokine Levels in Elderly Males and Females

There exists a close relationship between cardiovascular diseases and chronic kidney disease. Apolipoprotein A1 and high-density lipoprotein (HDL) cholesterol are widely used as cardiovascular risk markers but they also have anti-inflammatory properties. The aim of this study was to investigate any associations between HDL levels and cytokine levels in urine. We randomly selected 90 urine samples from the Prospective Investigation of the Vasculature in Uppsala Seniors Study (41 males and 49 females). The samples were analyzed with 2 multiplex assays, Multiplex Inflammation I and Cardiovascular II kits (Olink Bioscience, Uppsala, Sweden). We analyzed the correlations between 158 cytokines in urine with apolipoprotein A1, HDL cholesterol, apolipoprotein B, and low-density lipoprotein cholesterol. There were strong correlations for apolipoprotein A1 and HDL cholesterol with individual cytokines. After adjustment for multiplicity testing, there were 33 significant correlations between apolipoprotein A1 and cytokine levels and 14 of these were also significantly correlated with HDL cholesterol. The strongest associations were observed for IL-1α, SPON2, RAGE, PAR-1, TRAIL-R2, IL-4RA, TNFRSF11A, and SCF. A total of 28 out of 33 correlations were negative, indicating a negative relationship between apolipoprotein A1 and urinary cytokines. The study shows a negative correlation between apolipoprotein A1 and HDL cholesterol and urinary cytokine levels. The finding is in agreement with the anti-inflammatory properties of HDL.

Lower creatinine concentration values and lower inter-laboratory variation among Swedish hospital laboratories in 2014 compared to 1996: results from the Equalis external quality assessment program

Background

Creatinine measurement for estimation of glomerular filtration rate (GFR) is a frequently used laboratory test. Differences in analytic creatinine methods have caused large inter-laboratory variation. International and national standardization efforts have been made in the last decade.

Methods

This study describes the results of the standardization efforts in Sweden by summarizing data for creatinine concentration in blood plasma in the Equalis quality assessment program during 1996–2014.

Results

Non-compensated Jaffe methods dominated in 1996–2001 (91 of 103 laboratories; 90%) and were then gradually replaced by either compensated Jaffe methods or enzymatic creatinine methods. In 2014 a majority of Swedish hospital laboratories (139 of 159; 87%) used enzymatic methods. The reported mean creatinine value by the Swedish laboratories was about 10 μmol/L higher than the isotope dilution mass spectrometry (IDMS) assured reference value in 2003, but consistent with the reference value from 2009 to 2014. The inter-laboratory CV was 7%–9% for creatinine values until 2007, and thereafter gradually decreased to about 4%–5% in 2014.

Conclusions

The introduction of enzymatic methods in Swedish laboratories has contributed to achieving a low inter-laboratory variation. Also, the reported values are lower for enzymatic methods compared to Jaffe methods, and the values obtained with enzymatic methods were consistent with IDMS certified values established at reference laboratories. Thus, many Swedish hospital laboratories reported 10 μmol/L lower, and more true, creatinine concentrations in 2012 than in 2003, which may cause bias in longitudinal studies.

Evaluation of Nova StatStrip and FreeStyle Precision Pro blood ketone tests using 3-hydroxybutyrate doped samples

BACKGROUND

The most clinically useful blood ketone in the diagnosis, management, and recovery of diabetes ketoacidosis in both adults and children is 3-hydroxybutyrate. In the absence of laboratory routine methods, several point-of-care methods are in use, but very few clinical evaluations are published.

METHODS

This study evaluates linearity and reproducibility of two handheld point-of-care meters for blood 3-hydroxybutyrate measurement for hospital use, Nova StatStrip, and FreeStyle Precision Pro. Whole blood from healthy volunteers was spiked with different concentrations of a 3-hydroxybutyrate solution and tested on the point-of-care instruments. The results were compared with plasma 3-hydroxybutyrate that was analyzed with a laboratory enzymatic end point spectrophotometric reference method.

RESULTS

Blood 3-hydroxybutyrate on StatStrip was linear with the reference method up to approximately 4 mmol/L, and FreeStyle was linear up to 6 mmol/L. At higher concentrations, the point-of-care instruments gave falsely too low results, especially the StatStrip meter. The FreeStyle meter had better precision and less bias than StatStrip.

CONCLUSION

In the acute setting of diabetes ketoacidosis, blood 3-hydroxybutyrate in the higher ranges should be interpreted with caution as the point-of-care meters are less accurate there.

Seasonal variability of NT-proBNP in Swedish primary care patients

The aim of this study was to determine if there is a seasonal variation in the widely used heart failure marker NT-proBNP. The study included all primary care requests for NT-proBNP in the county of Uppsala, Sweden, between January 2007 and December 2015. For seasonal variation, the NT-proBNP results for individual months were compared. The NT-proBNP values were highest in July to September, but there was also a minor peak in December-January. In conclusion, a seasonal periodicity for NT-proBNP was demonstrated in primary care patients. The data could be useful for practitioners for evaluation of NT-proBNP results and monitoring of patients with heart failure.

Urinary Osteopontin Predicts Incident Chronic Kidney Disease, while Plasma Osteopontin Predicts Cardiovascular Death in Elderly Men

BACKGROUND AND OBJECTIVES

The matricellular protein osteopontin is involved in the pathogenesis of both kidney and cardiovascular disease. However, whether circulating and urinary osteopontin levels are associated with the risk of these diseases is less studied.

DESIGN SETTING PARTICIPANTS AND MEASUREMENTS

A community-based cohort of elderly men (Uppsala Longitudinal Study of Adult Men [ULSAM]; n = 741; mean age: 77 years) was used to study the associations between plasma and urinary osteopontin, incident chronic kidney disease, and the risk of cardiovascular death during a median of 8 years of follow-up.

RESULTS

There was no significant cross-sectional correlation between plasma and urinary osteopontin (Spearman ρ = 0.07, p = 0.13). Higher urinary osteopontin, but not plasma osteopontin, was associated with incident chronic kidney disease in multivariable models adjusted for age, cardiovascular risk factors, baseline glomerular filtration rate, urinary albumin/creatinine ratio, and the inflammatory markers interleukin 6 and high-sensitivity C-reactive protein (odds ratio for 1 standard deviation [SD] of urinary osteopontin, 1.42, 95% CI 1.00-2.02, p = 0.048). Conversely, plasma osteopontin, but not urinary osteopontin, was independently associated with cardiovascular death (multivariable hazard ratio per SD increase, 1.35, 95% CI 1.14-1.58, p < 0.001, and 1.00, 95% CI 0.79-1.26, p = 0.99, respectively). The addition of plasma osteopontin to a model with established cardiovascular risk factors significantly increased the C-statistics for the prediction of cardiovascular death (p < 0.002).

CONCLUSIONS

Higher urinary osteopontin specifically predicts incident chronic kidney disease, while plasma osteopontin specifically predicts cardiovascular death. Our data put forward osteopontin as an important factor in the detrimental interplay between the kidney and the cardiovascular system. The clinical implications, and why plasma and urinary osteopontin mirror different pathologies, remain to be established.

Albumin adjustment of total calcium does not improve the estimation of calcium status

BACKGROUND

There is a longstanding controversy as to whether plasma measurements of total calcium should be adjusted for albumin concentration, and if so which formulas are the most appropriate.

METHODS

Ionised calcium, total calcium and albumin results, analysed at the same time at Uppsala University Hospital Laboratory between February 2005 and June 2013, were retrieved from a laboratory information system. The dataset included results from 20,003 patients. Total calcium was albumin-modified by a locally derived formula, based on 3106 patients from the dataset, and formulas from the literature. The agreement between the reference method ionised calcium and unadjusted total calcium and the seven different albumin-modifying calcium formulas, respectively, were compared with intra-class correlation coefficients (ICC).

RESULTS

Total calcium showed substantial agreement to ionised calcium, ICC 0.85 (95% CI 0.84-0.86) for the whole validation cohort. Albumin-modified calcium by different formulas showed significantly less or equal agreement, however the locally determined formula performed better than formulas taken from the literature. Also, total calcium classified the patient as hypo-normo- or hypercalcemic right in 82% of the patients. The albumin-modified calcium did not classify patients significantly better except in the subgroup hypoalbuminemia (<30 g/L) where the local formula classified the patients slightly better than total calcium.

CONCLUSIONS

Albumin modification of total calcium determinations is unlikely to add valuable information, and this practice should be abandoned. Ionised calcium should be used more frequently when aberrant results for total calcium are followed up, or in patients with known hypoalbuminemia.

Seasonal variations of urate in a Swedish adult population

Seasonality in the incidence and prevalence of gout has previously been reported but the cause of this seasonality in gout is not explained. The aim of this study was to evaluate possible seasonal variations of urate in a large unselected Swedish adult population. We analyzed 170,915 urate test results from patients at a tertiary care hospital between 2000 and 2016. The results were divided according to sex and sampling month of the year. The median urate values were overall higher in males compared to females and both males and females had peak urate concentrations in the summer months (June–August). There is a seasonal pattern for urate concentrations in a large Swedish population similar to the previously reported seasonality for gout. This may be clinically important and could contribute to the circannual variation of gout. The seasonal pattern should be recognized when evaluating patient results both in clinical practice and in research studies.

Associations between urinary kidney injury biomarkers and cardiovascular mortality risk in elderly men with diabetes

AIM

Three urinary biomarkers, kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), and cystatin C, have been suggested as clinically relevant highly specific biomarkers of acute kidney tubular damage. Yet, the utility of these biomarkers in the prognostication of diabetic nephropathy has been less studied. Therefore, we aimed to investigate the longitudinal association between these urinary biomarkers and cardiovascular mortality in patients with diabetes.

METHODS

The study sample consisted of participants with diabetes in the community-based Uppsala Longitudinal Study of Adult Men (n = 91; mean age 77.8 years). During follow-up (median 8.3 years, interval 0.7-13.4 years), 33 participants died of cardiovascular causes.

RESULTS

In a multivariable Cox regression model adjusting for age, glomerular filtration rate, and urinary albumin/creatinine ratio, higher urinary KIM-1/creatinine was associated with an increased risk for cardiovascular mortality (HR per SD increase 1.51, 95% confidence intervals 1.03-2.24, P = 0.03). Neither urinary NGAL/creatinine nor urinary cystatin C/creatinine were independently associated with an increased cardiovascular mortality risk.

CONCLUSION

In elderly men with diabetes, higher urinary KIM-1/creatinine was associated with an increased long-term risk of cardiovascular mortality independently of established markers of diabetic nephropathy. Our data provide support for kidney tubular damage as an important aspect of diabetic nephropathy that merits further investigation.

Urinary KIM-1, but not urinary cystatin C, should be corrected for urinary creatinine

OBJECTIVES

The interest for tubular damage markers such as urinary cystatin C (U-CystC) and kidney injury molecule-1 (U-KIM-1) grows, especially for the diagnosis of acute kidney injury. The trend to measure proteins in spot urine samples instead of 24-h urine collections calls for adjustment of urine dilution with urinary creatinine (UCr). However, it is not known whether UCr adjustment provides a more true value of basal U-CystC and U-KIM-1 levels than absolute values.

DESIGN & METHODS

This study examines the rationale for UCr correction for U-CystC and U-KIM-1 by exploring the linear relations between U-CystC and U-KIM-1 and UCr, respectively, and the biological day to day variation of absolute concentrations and UCr adjusted values of the two biomarkers.

RESULTS

Both U-CystC and U-KIM-1 concentrations correlated positively with UCr (R=0.37, P<0.001 and R=0.62, P<0.001, respectively) in 378 participants in a community cohort, which indicated a rationale for adjustment with UCr. However, U-CystC/Cr ratio associated negatively with UCr (R=- 0.31, P<0.001), which could indicate a certain amount of 'over-adjustment'. Morning urine collected for 10 consecutive days from 13 healthy volunteers showed a biological day to day variation of 82% for U-CystC, 75% for U-cystC/Cr ratio, 70% for U-KIM-1 and 46% for U-KIM-1/Cr ratio.

CONCLUSIONS

This study supports the use of U-KIM-1/Cr ratio in clinical population studies. Data supporting the use of U-CysC/U-Cr ratio were less convincing and the possible confounding of UCr has to be acknowledged in clinical settings.

Relationship of proximal tubular injury to chronic kidney disease as assessed by urinary kidney injury molecule-1 in five cohort studies

BACKGROUND

The primary biomarkers used to define CKD are serum creatinine and albuminuria. These biomarkers have directed focus on the filtration and barrier functions of the kidney glomerulus even though albuminuria results from tubule dysfunction as well. Given that proximal tubules make up ∼90% of kidney cortical mass, we evaluated whether a sensitive and specific marker of proximal tubule injury, urinary kidney injury molecule-1 (KIM-1), is elevated in individuals with CKD or with risk factors for CKD.

METHODS

We measured urinary KIM-1 in participants of five cohort studies from the USA and Sweden. Participants had a wide range of kidney function and were racially and ethnically diverse. Multivariable linear regression models were used to test the association of urinary KIM-1 with demographic, clinical and laboratory values.

RESULTS

In pooled, multivariable-adjusted analyses, log-transformed, creatinine-normalized urinary KIM-1 levels were higher in those with lower eGFR {β = -0.03 per 10 mL/min/1.73 m(2) [95% confidence interval (CI) -0.05 to -0.02]} and greater albuminuria [β = 0.16 per unit of log albumin:creatinine ratio (95% CI 0.15-0.17)]. Urinary KIM-1 levels were higher in current smokers, lower in blacks than nonblacks and lower in users versus nonusers of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers.

CONCLUSION

Proximal tubule injury appears to be an integral and measurable element of multiple stages of CKD.

The Roche Immunoturbidimetric Albumin Method on Cobas c 501 Gives Higher Values Than the Abbott and Roche BCP Methods When Analyzing Patient Plasma Samples

BACKGROUND

Serum/plasma albumin is an important and widely used laboratory marker and it is important that we measure albumin correctly without bias. We had indications that the immunoturbidimetric method on Cobas c 501 and the bromocresol purple (BCP) method on Architect 16000 differed, so we decided to study these methods more closely.

METHOD

A total of 1,951 patient requests with albumin measured with both the Architect BCP and Cobas immunoturbidimetric methods were extracted from the laboratory system. A comparison with fresh plasma samples was also performed that included immunoturbidimetric and BCP methods on Cobas c 501 and analysis of the international protein calibrator ERM-DA470k/IFCC.

RESULTS

The median difference between the Abbott BCP and Roche immunoturbidimetric methods was 3.3 g/l and the Roche method overestimated ERM-DA470k/IFCC by 2.2 g/l. The Roche immunoturbidimetric method gave higher values than the Roche BCP method: y = 1.111x - 0.739, R² = 0.971.

CONCLUSION

The Roche immunoturbidimetric albumin method gives clearly higher values than the Abbott and Roche BCP methods when analyzing fresh patient samples. The differences between the two methods were similar at normal and low albumin levels.

Cystatin C-based glomerular filtration rate associates more closely with mortality than creatinine-based or combined glomerular filtration rate equations in unselected patients

BACKGROUND

Decreased glomerular filtration rate (GFR) is an important cardiovascular risk factor, but estimated GFR (eGFR) may differ depending on whether it is based on creatinine or cystatin C. A combined creatinine/cystatin C equation has recently been shown to best estimate GFR; however, the benefits of using the combined equation for risk prediction in routine clinical care have been less studied. This study compares mortality risk prediction by eGFR using the combined creatinine/cystatin C equation (CKD-EPI), a sole creatinine equation (CKD-EPI) and a sole cystatin C equation (CAPA), respectively, using assays that are traceable to international calibrators.

METHODS AND RESULTS

All patients analysed for both creatinine and cystatin C from the same blood sample tube (n = 13,054) during 2005-2007 in Uppsala University Hospital Laboratory were divided into eGFR risk categories>60, 30-60 and <30 mL/min/1.73 m(2) by each eGFR equation. During follow-up (median 4.6 years), 4398 participants died, of which 1396 deaths were due to cardiovascular causes. Reduced eGFR was significantly associated with death as assessed by all eGFR equations. The net reclassification improvement (NRI) for the combination equation compared with the sole creatinine equation was 0.10 (p < 0.001) for all-cause mortality and 0.08 (p < 0.001) for cardiovascular mortality, indicating improved reclassification. In contrast, NRI for the combination equation, compared with the sole cystatin C equation, was -0.06 (p < 0.001) for all-cause mortality and -0.02 (p = 0.032) for cardiovascular mortality, indicating a worsened reclassification.

CONCLUSIONS

In routine clinical care, cystatin C-based eGFR was more closely associated with mortality compared with both creatinine-based eGFR and creatinine/cystatin C-based eGFR.

Comparison between Cystatin C- and Creatinine-Estimated Glomerular Filtration Rate in Cardiology Patients

OBJECTIVE

Estimation of the glomerular filtration rate (GFR) is essential for identification, evaluation and risk prediction in patients with kidney disease. Estimated GFR (eGFR) is also needed for the correct dosing of drugs eliminated by the kidneys and to identify high-risk individuals in whom coronary angiography or other procedures may lead to kidney failure. Both cystatin C and creatinine are used for the determination of GFR, and we aimed to investigate if eGFR by the two methods differ in cardiology patients.

METHODS

We compared cystatin C and creatinine (CKD-EPI) eGFR calculated from the same request from a cardiology outpatient unit (n = 2,716), a cardiology ward (n = 980), a coronary care unit (n = 1,464), and an advanced coronary care unit (n = 518) in an observational, cross-sectional study.

RESULTS

The median creatinine eGFR results are approximately 10 ml/min/1.73 m(2) higher than the median cystatin C eGFR that is up to 90 ml/min/1.73 m(2), irrespective of the level of care. Creatinine eGFR resulted in a less advanced eGFR category in the majority of patients with a cystatin C eGFR <60 ml/min/1.73 m(2).

CONCLUSIONS

Our study demonstrates a difference between creatinine and cystatin C eGFR in cardiology patients. It is important to be aware of which marker is used for the reported eGFR to minimize erroneous interpretations of the test results, as this could lead to under- or overmedication. Further studies are needed to determine the best method of estimating the GFR in cardiology units.

Estimation of the possible economic effects of a sequential testing strategy with NT-proBNP before echocardiography in primary care

BACKGROUND

The object of the study was to estimate the possible economic effects of a sequential testing strategy with NT-proBNP from a primary care payer perspective.

METHODS

The study data were collected from primary care physicians in the County of Uppland from 2005 through 2012. Two different cut-off levels were used for negative NT-proBNP in the rule-out test: 300 and 400 pg/mL. The cost-effectiveness of the testing strategy was estimated through the short-term cost avoidance and reduction in demand for echocardiographies.

RESULTS

The female patients were slightly older than the males. Based on the data from 2012, the estimated costs for NT-proBNP tests and echocardiographies per county were reduced by EUR 300000/100000 inhabitants with the 300 pg/mL cut-off and EUR 350000/100000 inhabitants with the 400 pg/mL.

CONCLUSIONS

The use of NT-proBNP as a rule-out test in a sequential testing strategy reduced the cost for diagnostic work-up of primary care patients with suspected heart failure.

Urinary kidney injury molecule-1 and the risk of cardiovascular mortality in elderly men

BACKGROUND AND OBJECTIVES

Kidney injury molecule-1 (KIM-1) has been suggested as a clinically relevant highly specific biomarker of acute kidney tubular damage. However, community-based data on the association between urinary levels of KIM-1 and the risk for cardiovascular mortality are lacking. This study aimed to investigate the association between urinary KIM-1 and cardiovascular mortality.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a prospective study, using the community-based Uppsala Longitudinal Study of Adult Men (N=590; mean age 77 years; baseline period, 1997-2001; median follow-up 8.1 years; end of follow-up, 2008).

RESULTS

During follow-up, 89 participants died of cardiovascular causes (incidence rate, 2.07 per 100 person-years at risk). Models were adjusted for cardiovascular risk factors (age, systolic BP, diabetes, smoking, body mass index, total cholesterol, HDL cholesterol, antihypertensive treatment, lipid-lowering treatment, aspirin treatment, and history of cardiovascular disease) and for markers of kidney dysfunction and damage (cystatin C-based eGFR and urinary albumin/creatinine ratio). Higher urinary KIM-1/creatinine (from 24-hour urine collections) was associated with a higher risk for cardiovascular mortality (hazard ratio per SD increase, 1.27; 95% confidence interval [95% CI], 1.05 to 1.54; P=0.01). Participants with a combination of high KIM-1/creatinine (upper quintile, ≥175 ng/mmol), low eGFR (≤60 ml/min per 1.73 m(2)), and microalbuminuria/macroalbuminuria (albumin/creatinine ratio≥3 g/mol) had a >8-fold increased risk compared with participants with low KIM-1/creatinine (<175 ng/mmol), normal eGFR (>60 ml/min per 1.73 m(2)), and normoalbuminuria (albumin/creatinine ratio<3 g/mol) (hazard ratio, 8.56; 95% CI, 4.17 to 17.56; P<0.001).

CONCLUSIONS

These findings suggest that higher urinary KIM-1 may predispose to a higher risk of cardiovascular mortality independently of established cardiovascular risk factors, eGFR, and albuminuria. Additional studies are needed to further assess the utility of measuring KIM-1 in the clinical setting.

Inflammatory biomarker pentraxin 3 (PTX3) in relation to obesity, body fat depots and weight loss

OBJECTIVE

The relation between inflammatory markers, adiposity and disease is under extensive study. Here we tested the hypothesis that the immunomodulatory protein pentraxin 3 (PTX3) is associated with adiposity in the general population.

METHODS

Serum PTX3 concentrations, body mass index (BMI), waist circumference (WC) and fat depots, as quantified by dual-energy X-ray absorptiometry and magnetic resonance imaging, were assessed in three community-based cohorts: ULSAM, n = 790, mean age 78 years; PIVUS, n = 1003, mean age 70 years, women 50%; and the NORDIET-trial, n = 86, mean age 53 years, women 63%. Participants were re-examined after 5 years (PIVUS, n = 804) or following a 6-week randomized controlled dietary intervention (NORDIET).

RESULTS

PTX3 levels were inversely associated with BMI and WC as well as with total and visceral fat (P < 0.05 for all; adjusted for age, inflammatory biomarkers and cardiovascular risk factors). The association between PTX3 and BMI appeared even stronger in nonobese individuals. A decrease in BMI over 5 years as well as weight loss following the NORDIET intervention were associated with increased serum PTX3 concentrations (P < 0.001).

CONCLUSIONS

These consistent data support an inverse association between circulating PTX3 and anthropometrical measures, calling for further mechanistic studies of the link between PTX3 and fat.

Circulating human fractalkine is decreased post-operatively after orthopedic and coronary bypass surgery

Fractalkine is an important chemokine involved in resolving normal inflammatory processes such as wound healing. Soluble fractalkine acts as a chemoattractant bringing cytotoxic and cytokine-producing cells to areas of inflammation. The aim of the present study was to investigate circulating fractalkine during inflammatory response induced by surgery.

MATERIALS AND METHODS

Fractalkine was analyzed in serum samples from orthopedic surgery patients (n=29) and coronary bypass patients (n=21). The samples were collected prior to surgery and 4 and 30 days after surgery, respectively.

RESULTS

Fractalkine concentrations decreased from pre-operative levels of 1,764 (1,330-2,434) pg/mL to 1,520 (1,330-2,434) pg/mL at 4 days after surgery, and to 1,285 (1,099-1,462) pg/mL 30 days after surgery in patients undergoing orthopedic procedures (p<0.01, 30 days post-operatively versus pre-operatively). Furthermore, fractalkine concentrations decreased significantly from pre-operative levels of 1,856 (1,520-2,434) pg/mL to 1,338 (964-1,650) pg/mL 4 days post-operatively and to 1,266 (1,080-1,338) pg/mL 30 days post-operatively in patients undergoing coronary bypass surgery (p<0.01, 30 days post-operative versus pre-operative values).

CONCLUSION

A significant and persistent decrease in circulating fractalkine was observed after orthopedic and coronary bypass surgery despite a marked inflammatory response.

Kidney injury molecule (KIM)-1 is associated with insulin resistance: results from two community-based studies of elderly individuals

BACKGROUND AND OBJECTIVES

Insulin resistance has been shown to be closely associated with glomerular filtration rate and urinary albumin/creatinine ratio, even prior to the development of diabetes. Urinary kidney injury molecule 1 (KIM-1) is a novel, highly specific marker of kidney tubular damage. The role of insulin resistance in the development of kidney tubular damage is not previously reported. Thus, we aimed to investigate the associations between insulin sensitivity (assessed by HOMA) and urinary KIM-1.

DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS

Two community-based cohorts of elderly individuals were investigated: Prospective Investigation of the vasculature in Uppsala seniors (PIVUS, n=701; mean age 75 years, 52% women); and Uppsala Longitudinal Study of adult men (ULSAM, n=533; mean age 78 years).

RESULTS

Lower insulin sensitivity was associated with higher urinary KIM-1 in both cohorts after adjustments for age, BMI, blood pressure, antihypertensive treatment, glomerular filtration rate, and urinary albumin-creatinine ratio (PIVUS: regression coefficient for 1-SD higher HOMA-IR 0.11, 95% CI 0.03-0.20, p=0.009, and ULSAM: 0.13, 95% CI 0.04-0.22, p=0.007). Results were similar in individuals without diabetes, with normal kidney function and normo-albuminuria.

CONCLUSIONS

Our findings in elderly individuals support the notion that the interplay between an impaired glucose metabolism and renal tubular damage is evident even prior to the development of diabetes and overt kidney disease.

Soluble TNF receptors and kidney dysfunction in the elderly

The importance of TNF-α and its soluble receptors (sTNFR1 and sTNFR2) in the development of kidney disease is being unraveled. Yet, community-based data regarding the role of sTNFRs are lacking. We assessed serum sTNFRs and aspects of kidney damage cross-sectionally in two independent community-based cohorts of elderly participants: Prospective Investigation of the Vasculature in Uppsala Seniors (n=815; mean age, 75 years; 51% women) and Uppsala Longitudinal Study of Adult Men (n=778; mean age, 78 years). Serum sTNFR1 correlated substantially with different aspects of kidney pathology in the Uppsala Longitudinal Study of Adult Men cohort (R=-0.52 for estimated GFR, R=0.22 for urinary albumin-to-creatinine ratio, and R=0.17 for urinary kidney injury molecule-1; P<0.001 for all), with similar correlations in the Prospective Investigation of the Vasculature in Uppsala Seniors cohort. These associations remained significant after adjustment for age, sex, inflammatory markers, and cardiovascular risk factors and were also evident in participants without diabetes. Serum sTNFR2 was associated with all three markers in the Prospective Investigation of the Vasculature in Uppsala Seniors cohort (P<0.001 for all). Our findings from two independent community-based cohorts confirm and extend results of previous studies supporting circulating sTNFRs as relevant biomarkers for kidney damage and dysfunction in elderly individuals, even in the absence of diabetes.

Urinary neutrophil gelatinase-associated lipocalin (NGAL) is associated with mortality in a community-based cohort of older Swedish men

OBJECTIVE

Neutrophil gelatinase-associated lipocalin (NGAL) indicates tubular kidney damage, neutrophil activation and possibly atherogenesis, however the prospective association between urinary NGAL (u-NGAL) and cardiovascular death in the community is not known.

METHODS

This study evaluates the association between urinary and serum NGAL and mortality in a Swedish population of 597 men aged 78 years. During the study (median follow-up 8.1 years) 261 men died, 90 of cardiovascular causes.

RESULTS

U-NGAL was associated with increased all-cause and cardiovascular mortality (HR 2.0 for quartile 4 vs. quartile 1, 95% CI 1.0-4.0, P < 0.05) in Cox regression models independently of cardiovascular risk factors, CRP and cystatin C estimated glomerular filtration rate (eGFRCysC) but not urinary Albumin (u-Alb). A combination of low eGFRCysC (≤60 mL/min), high u-Alb (≥3 mg/mmol Cr) and high u-NGAL (≥1.19 μg/mmol Cr) was associated with a 9-fold increased cardiovascular mortality (P < 0.001) and a 3-fold increased all-cause mortality (P < 0.001). Serum NGAL was associated with increased all-cause mortality risk independent of other cardiovascular risk factors (HR 1.4 for quartile 4 vs.1, 95% CI 1.0-1.9, P < 0.05) but not after adjustment with CRP, eGFRCysC or u-Alb.

CONCLUSION

This community study is the first to show that the tubular kidney biomarker u-NGAL associated with increased cardiovascular and all-cause mortality independent of cardiovascular risk factors and glomerular filtration. Additional research is needed to evaluate the utility of NGAL in clinical practice.

Urinary kidney injury molecule 1 and incidence of heart failure in elderly men

AIMS

There is growing recognition of the clinical importance of cardiorenal syndrome-the bidirectional interplay between kidney and cardiac dysfunction. Yet, the role of kidney tubular damage in the development of heart failure is less studied. The objective of this study was to investigate whether urinary kidney injury molecule (KIM)-1, a specific marker of tubular damage, predisposes to an increased heart failure risk.

METHODS AND RESULTS

This was a community-based cohort study [Uppsala Longitudinal study of Adult Men (ULSAM)] of 565, 77-year-old men free from heart failure at baseline. Heart failure hospitalizations were used as outcome. During follow-up (median 8.0 years), 73 participants were hospitalized for heart failure. In models adjusted for cardiovascular risk factors (age, systolic blood pressure, diabetes, smoking, body mass index, LDL/HDL ratio, antihypertensive treatment, lipid-lowering treatment, aspirin treatment, LV hypertrophy, and prevalent cardiovascular disease) and markers of kidney dysfunction and damage [cystatin C-based glomerular filtration rate (GFR) and urinary albumin/creatinine ratio], a higher urinary KIM-1/creatinine ratio was associated with higher risk for heart failure (hazard ratio upper vs. lower tertile, 1.81; 95% confidence interval 1.01-3.29; P < 0.05). Participants with a combination of low GFR (<60 mL/min/1.72 m(2)) and high KIM-1/creatinine (>128 ng/mmol) had a 3-fold increase in heart failure risk compared with participants with normal GFR and KIM-1 (P < 0.001).

CONCLUSION

Our findings suggest that kidney tubular damage predisposes to an increased risk for heart failure in the community. Further studies are needed to clarify the causal role of KIM-1 in the development of heart failure, and to evaluate the clinical utility of urinary KIM-1 measurements.

Day-to-day variation of urinary NGAL and rational for creatinine correction

OBJECTIVES

The number of clinical studies evaluating the new tubular biomarker urinary neutrophil gelatinase-associated lipocalin (U-NGAL) in urine are increasing. There is no consensus whether absolute U-NGAL concentrations or urinary NGAL/creatinine (U-NGAL/Cr) ratios should be used when chronic tubular dysfunction is studied. The aim was to study the biological variation of U-NGAL in healthy subjects and the rational for urinary creatinine (U-Cr) correction in two different study samples.

DESIGN AND METHODS

To study biological variation of U-NGAL and U-NGAL/Cr ratio and the association between U-NGAL and U-Cr in healthy subjects 13 young males and females (median age 29 years) collected morning urine in 10 consecutive days. Additionally, a random subsample of 400 males from a population-based cohort (aged 78 years) collecting 24-hour urine during 1 day was studied.

RESULTS

The calculated biological variation for absolute U-NGAL was 27% and for U-NGAL/Cr ratio, 101%. Absolute U-NGAL increased linearly with U-Cr concentration (the theoretical basis for creatinine adjustment) in the older males (R=0.19, P<0.001) and with borderline significance in the young adults (R=0.16, P=0.08). The U-NGAL/Cr ratio was, however, negatively associated with creatinine in the older males (R=-0.14, P<0.01) and in the young adults (R=-0.16, P=0.07) indicating a slight "overadjustment."

CONCLUSIONS

The study provides some support for the use of U-NGAL/Cr ratio but the rather large biological variation and risk of possible overadjustment need to be considered. Both absolute U-NGAL and U-NGAL/Cr ratios should be reported for the estimation of chronic tubular dysfunction.

Inflammation, oxidative stress, glomerular filtration rate, and albuminuria in elderly men: a cross-sectional study

Background

The role of inflammation and oxidative stress in mild renal impairment in the elderly is not well studied. Accordingly, we aimed at investigating the associations between estimated glomerular filtration rate (eGFR), albumin/creatinine ratio (ACR), and markers of different inflammatory pathways and oxidative stress in a community based cohort of elderly men.

Findings

Cystatin C-based GFR, ACR, and biomarkers of cytokine-mediated inflammation (interleukin-6, high-sensitivity C-reactive protein[CRP], serum amyloid A[SAA]), cyclooxygenase-mediated inflammation (urinary prostaglandin F2α [PGF2α]), and oxidative stress (urinary F2 isoprostanes) were assessed in the Uppsala Longitudinal Study of Adult Men(n = 647, mean age 77 years).

Results

In linear regression models adjusting for age, BMI, smoking, blood pressure, LDL-cholesterol, HDL-cholesterol, triglycerides, and treatment with statins, ACE-inhibitors, ASA, and anti-inflammatory agents, eGFR was inversely associated with CRP, interleukin-6, and SAA (β-coefficient −0.13 to −0.19, p < 0.001 for all), and positively associated with urinary F2-isoprostanes (β-coefficient 0.09, p = 0.02). In line with this, ACR was positively associated with CRP, interleukin-6, and SAA (β- coefficient 0.09-0.12, p < 0.02 for all), and negatively associated with urinary F2-isoprostanes (β-coefficient −0.12, p = 0.002). The associations were similar but with lower regression coefficients in a sub-sample with normal eGFR (>60 ml/min/1.73 m2, n = 514), with the exception that F2-isoprostane and SAA were no longer associated with eGFR.

Conclusion

Our data indicate that cytokine-mediated inflammation is involved in the early stages of impaired kidney function in the elderly, but that cyclooxygenase-mediated inflammation does not play a role at this stage. The unexpected association between higher eGFR/lower albuminuria and increased F2-isoprostanes in urine merits further studies.

Association between glomerular filtration rate and endothelial function in an elderly community cohort

BACKGROUND

Endothelial dysfunction is prevalent among individuals with chronic kidney disease. However, the association between glomerular filtration rate and endothelial function in the community is unclear and needs to be investigated in the general population.

METHODS

In the community-based Prospective Investigation of the Vasculature of Uppsala Seniors study (PIVUS, n = 952, mean age 70, women 49.3%), we investigated cross-sectional associations between estimated cystatin C-based glomerular filtration rate (eGFR), and 3 measures representing different aspects of endothelial function (endothelial-dependent vasodilation [EDV], endothelial independent vasodilatation [EIDV], and flow-mediated dilatation [FMD]). We also performed pre-specified sub-group analyses in participants with normal eGFR (>60 ml/min/1.73 m(2)).

RESULTS

In the whole cohort, 10 ml/min/1.73 m(2) higher eGFR was associated with 3% higher EDV (p = 0.001) and 2% higher EIDV (p = 0.007), adjusted for age and sex. The associations were attenuated and no longer statistically significant after adjusting for established cardiovascular risk factors. In participants with eGFR >60 ml/min/1.73 m(2), 10 ml higher eGFR was associated with 2% higher EDV (p = 0.04) after adjusting for sex and age. eGFR was not associated to FMD in any model or sub-sample.

CONCLUSION

This community-based study suggests that eGFR is associated with endothelial function also in persons with normal kidney function, but that this association is largely explained by confounding by established cardiovascular risk factors. Thus, our data do not support the notion of a direct causal interplay between renal and vascular function prior to the development of CKD.

Does consumption of two portions of salmon per week enhance the antioxidant defense system in pregnant women?

Salmon is a rich source of marine n-3 fatty acids, which may increase oxidative stress and, in turn, could affect the antioxidant defense system in blood plasma and erythrocytes of pregnant women. The Salmon in Pregnancy Study provided two meals of salmon per week to pregnant women from week 20 of gestation; the control group maintained their habitual diet low in oily fish. Higher selenium and retinol plasma concentrations were observed after dietary salmon supplementation. Besides, a concomitant increase in selenium and glutathione concentration as well as glutathione peroxidase and reductase activities were detected as pregnancy progressed. However, tocopherols, retinol, β-carotene, and coenzyme Q(10) decreased in late pregnancy. Collectively, our findings lead to the hypothesis that increased farmed salmon intake may increase antioxidant defenses during pregnancy. Clinical trials identifier NCT00801502.

24-Hour ambulatory blood pressure associates inversely with prostaglandin F(2α), interleukin-6 and F(2)-isoprostane formation in a Swedish population of older men

Vasoconstrictive prostaglandins (PGs), such as PGF(2α), F(2)-isoprostanes, and systemic inflammation may be involved in the physiological regulation of blood pressure (BP) and the pathophysiology leading to hypertension. However, studies evaluating these parameters and BP in human populations are sparse. We analysed the cross-sectional associations between 24-hour ambulatory BP and urinary 15-keto-dihydro-PGF(2α) (indicator of PG-mediated vasoconstriction and inflammation), plasma interleukin-6 (IL-6), C-reactive protein (CRP), serum amyloid A (SAA) and urinary F(2)-isoprostanes (indicator of vasoconstriction and oxidative stress) in 619 men in a Swedish older population (Uppsala Longitudinal Study of Adult Men, age 78 years). Both systolic and diastolic 24-hour BP correlated inversely with concentrations of 15-keto-dihydro-PGF(2α) (P<0.01) and F(2)-isoprostanes (P<0.01) independent on other cardiovascular risk factors. Additionally, diastolic 24-hour BP inversely correlated with plasma IL-6 (P<0.05) and 24-hour pulse pressure showed a positive linear correlation with IL-6, CRP and SAA. In conclusion, high BP is associated with decreased formation of vasoconstrictive PGF(2α) and F(2)-isoprostanes in this population of older men. These findings, although unlike our original hypothesis, might have an important physiological function which needs to be further evaluated.

Enhanced prostaglandin F2α formation in human pregnancy and the effect of increased oily fish intake: results from the Salmon in Pregnancy Study

Oily fish intake during pregnancy may reduce the risk of allergic diseases in infancy possibly by shifts in the fatty acid balance and subsequent altered prostaglandin (PG) formation. This intervention is the first study to evaluate if increased oily fish intake affects in vivo PGF(2α) formation during pregnancy. British pregnant women were randomised to two portions of farmed salmon weekly (n=47), or maintenance of their normal diet low in fish (n=41), from pregnancy week 20 until parturition. The concentrations of eicosapentaenoic and docosahexaenoic acids in plasma phosphatidylcholine (PC) were higher and the concentration of arachidonic acid in plasma PC was lower in the salmon group than the control group at weeks 34 and 38 of pregnancy. PGF(2α) formation was evaluated by urinary measurement of 15-keto-dihydro-PGF(2α), a major PGF(2α) metabolite, at 20, 34 and 38 weeks. In both the salmon and control groups urinary 15-keto-dihydro-PGF(2α) concentrations increased significantly during pregnancy, which may be of physiological importance. Oily fish intervention altered fatty acid concentrations but did not affect urinary 15-keto-dihydro-PGF(2α) concentrations in pregnant women.

Does increased intake of salmon increase markers of oxidative stress in pregnant women? The salmon in pregnancy study

The Salmon in Pregnancy Study provided two meals of salmon per week to pregnant women from week 20 of gestation; the control group maintained their habitual diet low in oily fish. Salmon is a rich source of marine n-3 fatty acids. Since marine n-3 fatty acids may increase oxidative stress, we investigated whether increased salmon consumption could affect markers of oxidative stress in mid and late pregnancy. Urinary 8-iso-prostaglandin F(2α), urinary 8-hydroxy-2'-deoxyguanosine, and plasma lipid peroxide concentrations did not change from week 20 to 38 of pregnancy and were not altered by increased consumption of salmon. Thus, increased intake of salmon during pregnancy does not increase oxidative stress, as judged by the markers of oxidative damage to lipids and DNA measured herein.