Serum Cystatin C Concentration As A Marker Of Early Renal Dysfunction In Essential Hypertention

Background and aims: The morbidity and mortality of essential hypertension has been increasing recently over the world, scr the hypertensive injury of kidney is a intractable problem clinically, which was the secondary disease resulting in end-stage renal idsease in western countries. In early stage, the hypertensive injury of kidney is difficulty to be detected with routine tests clinically. The measure of "gold standard" for glomerular filtration rate (GFR) is inulin clearances which is not used clinically with its complicated operation. Therefore, the GFR is usually evaluated by means of creatinine clearance(Ccr), or more conveniently by measuring serum creatinine concentration(Scr). However, serum creatinine concentration is increased only when the GFR is reduced by approximately 50%, and may be affected by many factors ( such as body metabolism, body mass, fever, etc.) , so the sensitivity and specificity is low. Now, it is very important to search some markers for early diagnosis of the hypertensive injury of kidney.With the development of studies for hypertensive injury of kidney, many studies have demonstrated that the serum cystatin C is a good marker, with more sensitivity and specificity than Scr. Cystatin C is a cysteineproteinase inhibitor, which is not affected with other factors such as inflammatory processes, malignancy, body mass, fever et al. Structurally, cystatin C is a low molecular weight(about 13 000 Mr), positively charged molecule that is freely filtered at the glomerulus, so its concentration in serum is almost entirely determined by GFR. Cystatin C is elevated while the concentration of Scr is normal especially at the mild renal dysfunction, which is so called Creatinine-Blind Range. Urinary microalbumin(mALB )and N-acety-beta-D-glucosaminidase(NAG) are also sensitive markers to evaluate early renal glomerular/tubular damage.The purpose of this study was to investigate the values of the early markers (serum Cys C% Sci% urine mALB and NAG) for detecting the early renal disfunction in essential hypertention.Methods: 112 patients(67 male,49 female) with essential hypertension were enrolled in this study, who were in our hospital during March 2005 to September 2005,and we divided them into two groups : hypertension group(without diabetes) and hypertension with diabetes group. The clinical and demographic characteristics were recorded and the level of serum Cys C> Sc^ urinary mALB and NAG were measured on the first hospital ization day, and the data were analyzed with software SPSS 11.5.Results:1. The clinical and demographic characteristics of the patients: The period of hypertension was longer in hypertension with diabetes group(14.50 +10.81 year) than in hypertension group (9.32 + 10.48 year)( pO.Ol), and the level of blood sugar was significantly higher in hypertension with diabetes group(168.64 +143.65 mg/dl) than in hypertension group (91.90 + 9.23 mg/dl)( p<0.01),while there was no significant difference in gender, age ,BMI and blood pressure between the two groups.2. Serum Cys C> Scr and NAG of the two groups was in normal limits. Only the urinary mALB in hypertension with diabetes group exceeded normal limits;there was no significant difference in Cys C. Scr between the two groups. Urinary mALB and NAG in hypertension with diabetes group significantly increased than the other group(p<0.05).3. All the measured index was calculated into abnormal rate:the abnormal rate of serum Cys C> Scr> urinary mALB and NAG in hypertension group was respectively 6. 12%. 0. 00% > 16.33% and 20.41%;in hypertension with diabetes group was 11. 11%. 11.11%, 49.21% and 34.92%;In comparison with the rate in the former group, the abnormal rate of Scr and urinary mALB in hypertension with diabetes group significantly increased( pO.Ol).4. The correlation analysis of variables: The creatinine clearance(Ccr) was calculated with the Cockcroft and Gault (C&G)Formula: [140-age(years) ] Xbody weight/[0. 815Xplasma creatinine(umol/1)] (For women, the correction factor of 0.85 was used). Significant linear correlation was found between Cys C/ Scr and Ccr(r=-0. 236 and r=~0. 203 respectively, p<0. 05), while no significant linear correlation between urine mALB /NAG and Ccr.Conclusions:1. The renal disfunction was more severe in hypertension with diabetes group than in hypertension group.2. In the clinical assessment of hypertension early damage on kidney, serum Cys C, urinary mALB and NAG were sensitive markers, in which serum Cys C was more dependable.