Evaluation of plasma cystatin C as a marker for glomerular filtration rate in patients with type 2 diabetes.

AIM: To evaluate plasma cystatin C as a marker of the glomerular filtration rate in patients with type 2 diabetes and their age and sex-matched controls. MATERIALS AND METHODS: Forty-seven patients with one decade of type 2 diabetes and 51 non-diabetic control subjects were studied. Plasma cystatin C was measured by particle-enhanced turbidimetric immunoassay in a new application for the Hitachi 704 analyzer. For comparison, plasma creatinine and creatinine clearance were measured. The plasma clearance of 51Cr-EDTA by the single injection method was utilized as reference. RESULTS: In patients with type 2 diabetes the correlation coefficient between plasma cystatin C and the plasma clearance of 51Cr-EDTA was 0.774 (Spearman's coefficient) and that between plasma creatinine and the plasma clearance of 51Cr-EDTA was 0.556 (p = 0.001 for the difference). The correlation between creatinine clearance and the plasma clearance of 51Cr-EDTA was 0.411. In receiver operating characteristic (ROC) curve analysis the diagnostic accuracy of plasma cystatin C was significantly better than that of plasma creatinine (p = 0.047) or creatinine clearance (p = 0.001). The best diagnostic efficiency (98%) for cystatin C was obtained when the cut-off limit was set at 1.32 mg/l. In the control group the correlation coefficients were: between cystatin C and the plasma clearance of 51Cr-EDTA 0.627, between creatinine and the plasma clearance of 51Cr-EDTA 0.466 and between creatinine clearance and the plasma clearance of 51Cr-EDTA 0.416. The area under the ROC plot curve of cystatin C was also greatest in the control group, but the diagnostic accuracy of cystatin C was marginally better than that of either plasma creatinine (p = 0.05) or creatinine clearance (p = 0.08). Among the control subjects various non-renal causes may have interfered with cystatin C concentrations reducing the correlations. CONCLUSIONS: Cystatin C measurement is a more sensitive and specific test for GFR in patients with type 2 diabetes than plasma creatinine or its clearance, when GFR is normal or only slightly reduced. If an elevated cystatin C concentration is found, non-renal factors have to be excluded. The turbidimetric application described here can easily be applied for most clinical chemistry analyzers and is therefore useful in daily clinical practice.

Urinary albumin excretion rate is independently related to autonomic neuropathy in type 2 diabetes mellitus.

OBJECTIVE: To evaluate if urinary albumin excretion rate (UAER) is independently related to subclinical autonomic neuropathy in type 2 diabetes. DESIGN: A controlled cross-sectional study. SETTING: Primary health care centre. SUBJECTS: Consecutive recently diagnosed (< 1 year) type 2 diabetic patients (group A, n = 150) and patients with long-standing (median 11 years) type 2 diabetes (group B, n = 146) chosen at random. A nondiabetic control group (group C, n = 150) matched for age and gender to group A. MAIN OUTCOME MEASURES: Neuropathy by cardiovascular reflex tests and UAER by nephelometry. METHODS: Univariate statistics in group A + B (t-test chi 2- or McNemars test) with Valsalva and breathing ratios as categorical grouping variables and the independent variables gender, smoking, systolic and diastolic blood pressure, fasting serum cholesterol, HDL cholesterol, triglycerides, haemoglobin A1c, glucagon stimulated C-peptide, fasting and postload 1 and 2 h blood glucose and serum insulin, UAER, coronary heart disease and congestive heart failure. Logistic regression analyses in group A + B with Valsalva and breathing ratios as dependent categorical variables and age, systolic blood pressure, congestive heart failure, coronary heart disease, fasting blood glucose, serum triglycerides and UAER as independent variables. RESULTS: Compared to nondiabetic subjects the diabetic patients of both groups were at increased risk of neuropathy as judged by the Valsalva ratio (P < 0.01). In known diabetic patients with a UAER > or = 30 mg 24-1 h neuropathy was more common than amongst their normoalbuminuric counterparts (Valsalva test P = 0.007, breathing test P = 0.02). In logistic regression analysis UAER independently explained abnormal Valsalva (P = 0.015) and breathing tests (P = 0.04) in the group A + B. CONCLUSIONS: UAER is independently related to subclinical autonomic neuropathy in type 2 diabetes.

Urinary albumin excretion rate and its determinants after 6 years in non-insulin-dependent diabetic patients.

BACKGROUND: The present study was undertaken to clarify the progression of urinary albumin excretion rate (UAER) in non-insulin-dependent diabetic (NIDD) patients 6 years after diagnosis, and to elucidate the risk factors of nephropathy. METHODS: This is a population-based controlled (baseline) cohort study. The prospective evaluation utilized the diabetic patients as internal controls. The setting was an urban primary health care centre. Main outcome measures were the UAER-24 h and fractional urinary albumin excretion rate (FAC) and their relation to mean blood pressure, haemoglobin Alc, fasting serum insulin and cholesterol and renal size. RESULTS: UAER (mg/24 h) was increased (geometric mean, quartile 1 and 3) in the diabetic patients at baseline, compared to the non-diabetic control subjects; 21 (10 and 33) versus 12 (8 and 15), P = 0.0001 (Wilcoxon's rank test). The UAER-24 h was not increased in diabetic subjects at follow-up; 24 (7 and 49) P = 0.3791 versus diabetic subjects at baseline. Eighteen per cent of normoalbuminuric (UAER < 30mg/24 h) patients developed microalbuminuria (UAER = 30-300 mg/24 h) and 3% clinical nephropathy (UAER > 300 mg/24 h). Of the microalbuminuric subjects 19% progressed to clinical nephropathy, 46% remained microalbuminuric and 35% remitted to normoalbuminuria. Serum insulin concentration, after assessment of confounding factors, measured at the baseline predicted the UAER for all diabetic subjects at follow-up in multiple linear regression analysis in an independent and significant way (P = 0.01). Serum insulin concentration (P = 0.034) and diuretic therapy (P = 0.050) at baseline independently predicted the outcome of the categorical variable progressor/nonprogressor (n = 22/86) based on the UAER-24 h at baseline and at follow-up. CONCLUSIONS: Progression of the UAER during the first 6 years is found among approximately every fifth NIDD subject who develops either microalbuminuria (from normoalbuminuria) or clinical nephropathy (from microalbuminuria). The role of serum insulin (insulin resistance) or some factor associated with it, is suggestive in the genesis of kidney disease.

Occurrence of late specific complications in type II (non-insulin-dependent) diabetes mellitus.

The objective of the present study was to determine the occurrence of late specific complications, i.e., nephropathy, retinopathy, and autonomic neuropathy, in type II (non-insulin-dependent) diabetic subjects with a recent onset and with a disease duration of at least 5 years. The study design comprised of a population-based controlled cross-sectional survey of middle-aged type II diabetic subjects in the City of Tampere, Southwest Finland. The mean (SD) albumin excretion rate per 24 h was found to have increased in recently diagnosed diabetic subjects, i.e., 54 (111) mg (p < 0.0001), and in long-term diabetic subjects, 134 (479) mg (p < 0.0001), compared to nondiabetic controls, 16 (19) mg. Microalbuminuria (30 mg/24 h < or = albumin excretion rate < or = 300 mg/24 h) was detected in 8% of nondiabetic subjects and in 29% of recently diagnosed subjects and 27% of long-term diabetic subjects. The prevalence of clinical nephropathy (albumin excretion rate > 300 mg/24 h) was 7% in long-term and 4% in recently diagnosed diabetic subjects and zero in nondiabetic subjects. The differences between diabetic and nondiabetic subjects tested for microalbuminuria and clinical nephropathy were significant (p = 0.02-0.0001) exempting the difference between recently diagnosed female diabetic subjects and nondiabetic female subjects tested for clinical nephropathy. Seventy-five percent of biopsied diabetic subjects with an albumin excretion rate exceeding 100 mg/24 h were found to have diabetic glomerulosclerosis, while the rest had a normal finding. In long-term diabetic subjects the prevalence of nonspecific, background and proliferative retinopathies were present in 40%, 31%, and 8%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Glomerular filtration rate and kidney size in type 2 (non-insulin-dependent) diabetes mellitus.

The objective of the present study was to estimate glomerular filtration rate and kidney size in recently diagnosed and long-term type 2 (non-insulin-dependent) diabetic subjects. The study design comprised of a population-based controlled cross-sectional survey of middle-aged type 2 diabetic subjects in the City of Tampere, Southwest Finland. One hundred and fifty consecutive recently diagnosed and 146 long-term middle-aged type 2 diabetic subjects with a disease duration of at least five years and one hundred and fifty age- and sex-matched (to recent diabetic subjects) non-diabetic control subjects were recruited. The glomerular filtration rate by single-shot 51Cr-EDTA clearance and kidney size by native X-ray tomography were measured. The glomerular filtration rate (ml/min/1.73 m2) was increased in both recently diagnosed (males 121 [27] and females 112 [27]) and long-term (males 123 [24] and females 102 [36]) diabetic subjects (corrected for age) compared to control subjects (males 111 [26] and females 93 [17]). The kidney areas (cm2) were greater in both recent diabetic (males 116.6 [15.4] and females 99.1 [15.3] and long-term diabetic (males 118.3 [15.8] and females 100.4 [15.2]) subjects than in the control group (males 104.3 [12.0] and females 88.6 [12.0]). All differences between diabetic subjects and non-diabetic subjects were statistically significant (p < 0.05), except that between long-term diabetic and non-diabetic females for glomerular filtration rate (p = 0.07). Analyzed by linear regression glomerular filtration rate was related to kidney area in all study groups and to hemoglobin A1c in long-term diabetic males.(ABSTRACT TRUNCATED AT 250 WORDS)