A11(T)
SPECTROPHOTOMETRIC ANALYSIS IN ESTIMATION OF 24-H SODIUM
EXCRETION FROM A SPOT URINE SAMPLE FOR EARLY DETECTION OF
RENAL TUBULOINTERSTICIAL TISSUE LESION IN PATIENTS WITH ARTERIAL
HYPERTENSION AND CHRONIC HEART FAILURE
Oganezova L, Arutyunov G
Russian State Medical University
BACKGROUND: Monitoring of sodium intake is clinically relevant due to ability of
excessive sodium intake to increase BP, reduce response to antihypertensive drug therapy.
Besides according to several researches tubulointersticial tissue (TIT) injury in patients with
arterial hyprtension (AH) and heart failure (HF) is prior to glomerular disfunction,
hyperfiltration and microalbuminuria due to endothelial dysfunction, hypoxia and oxidative
injury and long before proteinuria damages TIT. To prevent progressive kidney lesion and GFR
decline the purpose was to develop method for TIT injury detection. 24-h urine collection is
embarrassing, dipstick method has several disadvantages due to difficulties of results
interpretation and imperfect dipstick calibration for creatinine concentrations. Developed
method must be fast and easy for screening of large patient population.
METHODS: This pilot study included 34 patients with AH and 64 patients with HF 1-2 FC
(NYHA) with normal serum creatinine level and GFR. F/M=52/46, mean age was 57.5±8.7,
BMI=24.2±3.86 kg/m2. Salt intake was 2 g per 24 hours. All subjects submitted 24-h urine
collections along with an urine sample collected in the late afternoon/early evening before
dinner. Predicted 24-h sodium excretion was then determined from the spot urine
chloride/creatinine ratio using developed diagnosticum for portable spectrophotometric device.
Both ratios were adjusted for 24-h creatinine excretion. The level of nitrat-ion (N+) was
detected using spectrophotometric analysis. Augmentation index (AI) was measured with
applanation tonometry. Renal biopsy was performed in 7 patients. Statistical analysis was
performed using Statistica 6.0 Software for non-parametric parameters.
RESULTS: Predicted sodium excretion from spot urine correlated strongly with actual 24-h
sodium excretion, both for spectrophotometric analysis (r = 0.75; p=0.014), and the laboratory
method (r = 0.79, P= 0.003). In patients with more difference between sodium intake and
excretion there was more significant TIT fibrosis, confirmed by high gene expression of 6Ckine,
IL-8, MMP-3,7 and 9, urocinasa R, CXCR5, higher levels of higher levels of soluble adhesion
molecules (sVCAM-1 and sICAM-1) in renal biopsy. Significant decrease of N+ urine level
was associated with decrease of natriiuresis and increased AI, that can be an evidence of
vasoconstriction, increased rigidity of vessel wall due to sodium retention and ischemic damage
of TIT. 
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CONCLUSIONS: Developed spectrophotometric analysis appears promising as a convenient
and inexpensive means to serially assess 24-h sodium excretion in patients with AH and HF.
This express-method has showed the role of calculated delta between sodium intake and its
excretion and it can be effective in detection of early TIT injury. This express-method is
inexpensive, quantitive and accurate, it can be used as screening method in large population of
patients with AH and HF. Early detection of TIT injury and start of treatment can prevent
progressive loss of kidney function, decrease the number of patients with terminal kidney
failure requiring replacement therapy and burden of health systems for managing these patients.