Microalbuminuria: a sensitive indicator of non-renal disease?

Association of Urinary Albumin:Creatinine Ratio with Outcome of Children with Sepsis

Objective

The aim of the study was to investigate the association of urinary albumin:creatinine ratio (ACR) with regard to the outcome of sepsis patients and to study the trends of ACR with severity of disease, organ dysfunction, microcirculation status, the use of inotrope, and mechanical ventilation use, and length of pediatric intensive care unit (PICU) stay.

Materials and methods

In the prospective observational study, the patients with varying categories of sepsis admitted in the PICU with stay >24 hours were enrolled consecutively. Urine samples were collected at the time of admission (ACR1), 12 hours (ACR2), and 24 hours (ACR3).

Results

One hundred and thirty-eight patients including 56 cases of sepsis, 31 of severe sepsis, 22 of septic shock, and 29 of multiorgan dysfunction syndrome (MODS) cases were analyzed. There were 29 (21%) deaths. ACR (median, IQR) was significantly higher in nonsurvivors [ACR1 198.9 (111.2–329.4) vs 124.5 (59.37–294.5), p 0.03], [ACR2 213.8 (112.5–350) vs 117.8 (62.6–211.9) p 0.008], [ACR3 231.8 (99.9–441.2 vs 114.4 (44.1–240.3), p 0.005]. The ACR is increased progressively with the increasing severity of sepsis (p < 0.001). The performance of ACR operative characteristics was compared with that of PRISM and PELOD scores. In deceased, ACR was significantly correlated with blood pH, lactate, and base deficit. A cutoff value of ACR 102.7 mg/g had sensitivity 86.2%, specificity 40.4%, positive predictive value 27.8%, and negative predictive value 91.7%. The use of inotropes, mechanical ventilation (>48 hours), and mortality was significantly higher in patients with ACR >102 mg/g. The probability of death varied from 17.6 to 19% in the first 24 hours of admission. ACR was significantly cheaper as compared to PRISM score and PELOD score estimations.

Conclusion

Urinary ACR, a cost-effective tool, correlates with the severity of sepsis and associated morbidity and mortality in children.

How to cite this article

Sachdev A, Raheja K, Gupta N, Chugh P. Association of Urinary Albumin:Creatinine Ratio with Outcome of Children with Sepsis. Indian J Crit Care Med 2020;24(6):465–472.

Low-dose hydrocortisone during severe sepsis: effects on microalbuminuria

OBJECTIVE

The aim of this study was to investigate the effect of low-dose hydrocortisone on glomerular permeability measured by the microalbuminuria to creatinine ratio (MACR) and on other markers of sepsis in severe septic patients.

DESIGN

Randomized prospective study.

SETTING

University intensive care unit.

PATIENTS

The study involved 40 patients with severe sepsis randomized into the hydrocortisone group (n = 20) and the standard therapy group (n = 20).

INTERVENTIONS

The hydrocortisone group received standard therapy plus a continuous infusion of hydrocortisone for 6 days, whereas the standard therapy group received only standard therapy.

MEASUREMENTS AND MAIN RESULTS

MACR, serum C-reactive protein, and procalcitonin concentrations were recorded every day from the day before the steroid therapy (T(0)) until the 6 days after (T(1), T(2), T(3), T(4), T(5), and T(6)). Concentrations in the hydrocortisone group and the standard therapy group were compared using Mann-Whitney test at each time. We also compared with Wilcoxon signed rank test the values determined in each group at T(0) with those at each subsequent time. Median MACR decreased from T(0) to T(6) in both patient groups; however, values were significantly lower in the hydrocortisone group from T(3) through to T(6). Median serum C-reactive protein also decreased from T(0) in both patient groups, with significantly lower values in the hydrocortisone group from T(3) through to T(6). There were no significant differences in procalcitonin between groups compared with baseline values or at any individual time point.

CONCLUSIONS

Low-dose hydrocortisone seems to reduce MACR and serum C-reactive protein but not procalcitonin in patients with severe sepsis. Further studies are needed to confirm these results and to understand the underlying molecular mechanisms.

Assessment of renal injury in vivo

The ICH S7A (Safety Pharmacology for Human Pharmaceuticals) guidelines specify that potential adverse pharmacologic effects of a test substance on renal function should be evaluated in supplemental studies when there is a cause for concern (ICH, 2001). For the most part, this can easily be accomplished by examination of the appropriate analytes in urine and blood collected as part of the routine preclinical safety studies. This review will serve as an overview of the selection, interpretation and limitations of standard clinical pathology methods (serum chemistry and urinalysis) for assessment of renal function in such studies, as well as provide some information on emerging biomarkers of renal function.

Microalbuminuria is associated with impaired glomerular permselectivity in lymphoma patients

Slightly increased urinary albumin excretion is frequently found in patients with lymphoma and other malignancies but the pathophysiological mechanisms have yet to be clarified. In this study, parameters of renal function in lymphoma patients with microalbuminuria were evaluated. Sixty-seven patients with histologically proven diffuse large B-cell lymphoma were included in the study at diagnosis. Urinary albumin excretion was measured by immunoturbidimetry and microalbuminuria was defined as an excretion rate between 20 and 200 microg/min. Glomerular function was further estimated by renal clearance of creatinine and IgG, and the IgG/IgG4 charge selectivity index. Tubular function was evaluated by renal clearance of beta(2)-microglobulin. The median value of IgG clearance was increased in the microalbuminuric patients (0.22 versus 0.18 microl/min; p = 0.03). The median selectivity index was significantly lower in patients with microalbuminuria (1.0 versus 2.2; p<0.0001). Urinary albumin excretion was correlated with both the renal clearance of IgG (p<0.0001) and the selectivity index (p<0.0001). These data suggest that a slightly elevated level of urinary albumin excretion in a population of patients with aggressive lymphoma reflects altered glomerular permselectivity probably due to a defect in charge selectivity. The glomerular sieving dysfunction may be associated with an inflammatory response to the malignancy. Further studies are needed to validate the clinical impact of the renal parameters in lymphoma patients.

Vessel injury and capillary leak

OBJECTIVE

To understand the mechanism of pathologic capillary leak in the critically ill patient.

DESIGN

Review of normal and altered physiology of the microvasculature. Review of recent literature describing pathogenesis, mediators, and interventions influencing capillary leak and microvascular repair.

SETTING

In vitro and in vivo studies, the latter including animal and human subjects.

MEASUREMENTS AND MAIN RESULTS

Capillary leak with resultant edema develops in the critical care setting on the basis of perturbations in Starling's equation, primarily as a result of increased capillary permeability to larger molecules. This process is most likely fueled by inflammatory mediators or mechanical stress. Attempts to prevent or treat this process remain largely unsuccessful; resuscitation is more often symptomatic than therapeutic. Models of microvascular repair focus on discrete injury and may not be applicable to the recovery of capillary damage secondary to a systemic leak

CONCLUSIONS

Our understanding of capillary leak syndrome remains fragmented and weighted toward specific mediators contributing to the leak. The implications of extensive edema and the mechanism by which it resolves continue to be the subject of speculation rather than study.

The clinical application of a urine albumin:creatinine ratio point-of-care device

INTRODUCTION

Microalbuminuria is an accepted predictive marker for the early detection of renal disease and the identification of patients at high risk of developing complications of diabetes and hypertension. The Bayer Clinitek 50 is a urine chemistry point-of-care analyser for the semi-quantitative measurement of albumin and creatinine and calculation of albumin:creatinine ratio (ACR).

METHOD

Urine samples were obtained from 252 consecutive patients attending a city center diabetic clinic, and from 40 patients on admission to the ICU. Albumin and creatinine measurements were carried out using the Clinitek 50 and by the central laboratory.

RESULTS

The Clinitek 50 results agreed with the central laboratory results in 89% of the diabetic patient samples and 80% of the ICU patient samples. Excluding samples defined as normal by the Clinitek 50 (ACR<3.4 mg/mmol) would have resulted in an 80% reduction in samples sent to the lab for further quantification. The average length of stay in the group of ICU patients with normal ACR was significantly less than for those patients with an abnormal ACR (p<0.005).

CONCLUSIONS

The Clinitek 50 provides useful, immediate clinical information regarding the microalbuminuria status for use in the diabetic clinic setting or as a potential immediate risk management tool in intensive care.

Urinary excretion of albumin and retinol binding protein in systemic lupus erythematosus

We have measured the urinary excretion of total protein, albumin and retinol binding protein (RBP) in random urine specimens obtained from 40 female patients with systemic lupus erythematosus (SLE). Thirty-three of these patients had no clinical evidence of any renal impairment (non-renal SLE); seven had overt renal disease (renal SLE). RBP:creatinine ratios were significantly higher in non-renal SLE patients compared with female controls (P = 0.002). There was no significant difference between urine total protein concentrations, albumin:creatinine or total protein:creatinine ratios in non-renal SLE patients when compared with controls, despite approximately 20% of these patients having elevated excretion of total protein or albumin. All seven renal SLE patients had elevated albumin:creatinine ratios but only four of them had an increased RBP:creatinine ratio. Of 29 non-renal SLE patients who had urinary total protein concentrations below 0.2 g/L, (i.e. approximating to a negative protein dipstick), 14 had increases in either albumin or RBP:creatinine ratios. Only two patients had increases in both. In the absence of clinical evidence of renal disease, increases in urinary albumin or RBP excretion could indicate subclinical nephropathy and measurements may have a role in the early diagnosis and subsequent monitoring of renal disease in SLE.