The prognostic significance of proteinuria: the Framingham study

Urinary microalbumin as a marker for intermittent claudication

OBJECTIVE

The urinary microalbumin concentration was analysed in patients with intermittent claudication in order to investigate its usefulness as a marker for intermittent claudication.

MATERIALS AND METHODS

Urinary samples were collected prior to and following exercise in 15 patients with claudication. The patients walked on a treadmill as far as possible until they were stopped by pain. Urinary microalbumin concentration was measured by a latex agglutination system, and the result was considered abnormal when the concentration exceeded 10 mg/g creatinine. The ankle brachial pressure index (ABI) at rest and the time taken for the ankle pressure to return to the resting level following exercise (ABI recovery time) also were measured.

RESULTS

In seven (47%) of the patients, the urinary microalbumin concentration was elevated to more than 10 mg/g creatinine following exercise, while in eight (53%) it remained normal. The ABI recovery time was significantly longer in the patients in whom the microalbumin concentration was elevated, compared to that in patients without an elevated concentration. The urinary microalbumin concentration following exercise was reduced significantly when the walking distance was decreased 50% or 15%. Following vascular bypass surgery, the elevation in urinary microalbumin concentration was reduced.

CONCLUSIONS

The use of urinary microalbumin as a diagnostic marker for intermittent claudication is limited. However, in cases where the concentration is elevated, it can be used to follow the course of the disease.

Risk of developing end-stage renal disease in a cohort of mass screening

The prognostic significance of abnormal findings has not been demonstrated in a setting of mass screening. To evaluate the relative risk of end-stage renal disease (ESRD) indicated by various results of community-based mass screening, we utilized the registries of both community mass screening and chronic dialysis programs. In 1983, a total of 107,192 subjects over 18 years of age (51,122 men and 56,070 women) participated in dipstick urinalysis and blood pressure measurement in Okinawa, Japan. During ten years of follow-up, we identified 193 dialysis patients (105 men and 88 women) among them. Logistic regression analysis of clinical predictors of ESRD over 10 years was done and the adjusted odds ratio and 95% confidence interval were calculated in each of the predictors with adjustment to others. In the clinical predictors such as sex, age at screening, proteinuria, hematuria, systolic and diastolic blood pressure, proteinuria was the most potent predictor of ESRD (adjusted odds ratio 14.9, 95% confidence interval 10.9 to 20.2), and the next most potent predictor was hematuria (adjusted odds ratio 2.30, 95% confidence interval 1.62 to 3.28). Being of male gender was a significant risk factor for ESRD (adjusted odds ratio 1.41, 95% confidence interval 1.04 to 1.92). Diastolic blood pressure was also a significant predictor of ESRD (adjusted odds ratio 1.39, 95% confidence interval 1.17 to 1.64), but systolic blood pressure was not. In a mass screening setting, positive urine test, high diastolic blood pressure, and male sex were identified as the significant predictors of ESRD. Effect of glycosuria and other possible predictors of ESRD remained to be determined.

Lisinopril reduces postexercise albuminuria more effectively than atenolol in primary hypertension

Physical exercise causes transient albuminuria. The mechanisms of postexercise albuminuria are not fully clarified but stimulation of the reninangiotensin system (RAS) probably plays a major role through intrarenal haemodynamic changes causing an elevated filtration pressure. In a randomised, double-blind, crossover study we compared the effects on urinary albumin excretion (UAE) of lisinopril (L) and atenolol (A) therapy, i.e. we aimed to investigate whether inhibition of the RAS or inhibition of beta1-adrenoceptor-mediated effects of the sympathetic nervous system differed with regard to changes in UAE. Sixteen patients with uncomplicated primary hypertension were studied. Four standardised bicycle ergometer exercise tests were performed, before and after each active treatment period. UAE 30 min postexercise, determined by radioimmunoassay, was significantly lowered by both treatments: -278 mu g center dot min-1 (L) and -199 mu g center dot min-1 (A). The reduction of postexercise UAE achieved by treatment with the angiotensin-converting enzyme (ACE) inhibitor (L) was significantly greater than that achieved by the beta1-selective adrenoceptor blocker treatment. Blood pressure (BP) at rest and during exercise were equally reduced by both drugs. In conclusion, this study showed that antihypertensive treatment with an ACE inhibitor was more effective in reducing exercise-induced albuminuria than a beta1-selective adrenoceptor-blocking agent with a similar degree of BP reduction in patients with uncomplicated primary hypertension. This suggests that the RAS plays a major role in postexercise albuminuria in hypertensive subjects. The clinical significance of this finding, however, remains to be clarified.

Prevalence and prognostic significance of proteinuria in patients with lung cancer

The purpose of the present study was to ascertain the prevalence and prognostic significance of proteinuria in patients with lung cancer. Results of urinary dipstick testing were retrospectively reviewed in 1026 consecutive out-patients with histologically proven primary lung cancer and 475 consecutive out-patients with benign pulmonary disorders. Postoperative urinary dipstick test results were recorded in 243 surgically resected patients. Proteinuria was significantly more frequent in patients with lung cancer than in controls (30.1% vs 8.8%, p < 0.0001). The presence of proteinuria was significantly correlated with advanced disease stage (p < 0.0001). The frequency of proteinuria was significantly higher in patients with small cell carcinoma than in patients with other histologic types (p < 0.01). In the surgically resected patients, preoperative and postresection proteinuria occurred in 25.5% and 10.7% respectively (p < 0.0001). Patients with malignancies and proteinuria had significantly poorer survival than patients with normal urinary protein excretion (p < 0.0001). In a multivariate analysis including TNM stage, histologic type, sex, and age, proteinuria continued to be a significant predictor of reduced survival time. Our results suggest a high prevalence of increased urinary protein excretion in patients with primary lung cancer. Proteinuria may also be an independent predictor of poor survival.

Impaired endothelial function in patients with nephrotic range proteinuria

Proteinuria is associated with increased cardiovascular morbidity and mortality. Release of nitric oxide by the endothelium has been advanced as an important defense mechanism against vessel-wall damage. In the present study we therefore tested the hypothesis that proteinuria is associated with a defect in nitric oxide-dependent vasodilation, by using venous occlusion plethysmography of the forearm in nine patients with nephrotic range proteinuria (> 3.5 g/24 hr) and normal renal function (creatinine 83.1 +/- 8.7 mumol/liter), eight patients with active glomerulonephritis but normal renal function (creatinine 81.2 +/- 5.4 mumol/liter) and low range proteinuria (< 1.0 g/24 hr), and ten healthy volunteers. We infused L-NMMA (2 mg/min) to inhibit basal nitric oxide production, serotonin (0.1, 0.3 and 1.0 ng/kg/min) as an endothelium-dependent vasodilator, and nitroprusside (1, 10, 30 and 100 ng/kg/min) as an endothelium-independent vasodilator into the brachial artery. Administration of L-NMMA decreased basal forearm vascular resistance (FVR) by 30 +/- 4% in the nephrotic subjects, 38 +/- 4% in the non-nephrotic patients and by 37 +/- 2% in the healthy controls (P = 0.15). Upon the highest dose of serotonin FVR decreased in nephrotic subjects by 40 +/- 5%, which was less than in non-nephrotic patients (56 +/- 3%; P < 0.05) or in healthy controls (55 +/- 3%; P < 0.05). The maximal decrease in FVR upon nitroprusside infusion was not different between the groups (respectively 84 +/- 2, 84 +/- 3 and 84 +/- 2%). The impaired serotonin-induced vasodilation could be attributed to a defect in nitric oxide production, since L-NMMA almost completely prevented serotonergic vasodilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Thromboxane and neutrophil changes following intermittent claudication suggest ischaemia-reperfusion injury

OBJECTIVES

It has been postulated that ischaemia-reperfusion occurs in intermittent claudication resulting in neutrophil activation and release of soluble mediators, increasing systemic vascular permeability and enhancing atherogenesis.

METHODS

We measured neutrophil deformability, plasma thromboxane levels, and urinary microalbumin excretion in 30 male claudicants, and 10 age- and sex-matched controls, before and after exercise to maximum walking distance. Blood was taken from an antecubital vein.

RESULTS

There was an increase in urinary microalbumin excretion after exercise in claudicants. Statistically significant increases in the median and 90th percentile transit times (markers of neutrophil deformability) for isolated neutrophils from blood drawn 5 min after exercise in the claudicants were observed with no change in control subjects. Plasma thromboxane concentrations in claudicants increased within 10 min post-exercise. Plasma concentrations in controls were significantly lower throughout the study period. In the claudicant group, a positive correlation between the percentage change in the median transit time for neutrophils, and the percentage change in plasma thromboxane at 60 min post-exercise was found.

CONCLUSIONS

The results lend further support to the concept of ischaemia-reperfusion events in patients with intermittent claudication, leading to a systemic increase in vascular permeability as a result of endothelial injury or dysfunction (a crucial step in atherogenesis), associated with thromboxane production and neutrophil activation. We suggest that the above changes may contribute to the increased mortality seen in such patients.

Albumin excretion and vascular deaths in NIDDM

Non-insulin-dependent diabetes mellitus (NIDDM) is associated with premature mortality, generally thought to be exaggerated in patients with microalbuminuria. This prospective 8-year follow-up study aimed to determine outcome, mortality and cause of death in NIDDM patients with abnormal urinary albumin excretion compared to those with normal albumin excretion. We recruited 153 NIDDM patients with abnormal urinary albumin excretion and 153 control subjects with albumin excretion within the normal non-diabetic range, matched for age, sex and duration of diabetes, from three University hospital diabetic clinics in Newcastle upon Tyne. The outcome measures were status at follow-up, mortality and cause of death. Subjects with abnormal albumin excretion had a significantly higher 8-year mortality than matched control subjects (Odds Ratio 1.47, p = 0.02; 108 vs 66 per 1000 person years follow-up, p < 0.001). This difference was seen at all levels of abnormal albumin excretion, from just outside the normal range (10.6-29.9 microgram/min: 104 vs 61 per 1000 person years follow-up, p < 0.001) to more conventional definitions of microalbuminuria (> or = 30 micrograms/min: 111 vs 71 per 1000 person years follow-up, p < 0.01). Those with abnormal albumin excretion had an excess of vascular deaths compared to matched control subjects (Odds Ratio 1.70, p = 0.009), again at different levels of albumin excretion (10.6-29.9 micrograms/min p < 0.01, 30-150 micrograms/min p < 0.05). On multivariate analysis, age, initial ischaemic heart disease and initial albumin excretion rates were independent predictors of death from all causes.(ABSTRACT TRUNCATED AT 250 WORDS)

Proteinuria and mortality in diabetes: the WHO Multinational Study of Vascular Disease in Diabetes

The relation between proteinuria and mortality was investigated in 1188 patients with Type 1 diabetes and 3234 patients with Type 2 diabetes, aged 35-55 at baseline and followed up for a mean of 9.4 +/- 3.1 years in the WHO Multinational Study of Vascular Disease in Diabetes. Baseline prevalence of light or heavy proteinuria was the same (25%) in both types of diabetes after adjustment for differences in diabetes duration. Compared with patients with no proteinuria, all cause mortality ratios were 1.5 (95% confidence interval 1.1-2.0) and 2.9 (2.2-3.8) for Type 1 patients with light and heavy proteinuria, respectively, and 1.5 (1.2-1.8) and 2.8 (2.3-3.4) for Type 2 patients, after adjustment for age, duration of diabetes, blood pressure, cholesterol, and smoking. Proteinuria was associated with significantly increased mortality from renal failure, cardiovascular disease, and all other causes of death. In both types of diabetes, the association was strongest for renal deaths, and of similar magnitude for cardiovascular and all other causes of death. In conclusion, proteinuria is a common, important, and rather non-specific risk factor for increased morbidity and mortality in diabetes. The relation of proteinuria to mortality is similar for both types of diabetes. The benefits and risks of proteinuria reduction should be examined in large randomized trials with clinical endpoints.

Renal effects of nifedipine and captopril in patients with essential hypertension and reduced renal reserve

In this study we investigated the short-term effects of calcium channel blockers and angiotensin-converting enzyme inhibitors on renal hemodynamics and the urinary excretion of proteins with different relative mass in subjects with mild to moderate essential hypertension and apparently normal glomerular filtration rate but reduced renal functional reserve. Sixteen subjects underwent the following four treatments: (1) low-protein meal (0.2 g protein/kg body wt), (2) high-protein meal (1.3 g protein/kg body wt), (3) high-protein meal plus oral nifedipine (20 mg), and (4) high-protein meal plus oral captopril (50 mg). Two urine samples were obtained after meals. Blood samples were drawn at the midpoint of each 120-minute urine collection period. Urine and serum were tested for total protein, immunoglobulin G, albumin, alpha 1-microglobulin, retinol binding protein, and beta 2-microglobulin. Glomerular filtration rate and renal plasma flow were assessed by iothalamate and p-aminohippuric clearance, respectively. Compared with the high-protein meal alone, nifedipine elicited a clear-cut increase in the urinary excretion of total protein (+60%, P < .01), immunoglobulin G (+58%, P < .01), albumin (+25%, P < .05), retinol binding protein (+47%, P < .05), and beta 2-microglobulin (+52%, P < .05); captopril decreased the urinary excretion rate of immunoglobulin G (-26%, P < .05), albumin (-22%, P < .05), and beta 2-microglobulin (-34%, P < .05). The ratio between the clearances of immunoglobulin G and albumin was higher after nifedipine (+21%, P < .01) and unchanged after captopril (-9%, P = NS) compared with the high-protein meal alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Microalbuminuria in 411 untreated individuals with established hypertension, white coat hypertension, and normotension

We compared urinary albumin excretion in normotensive subjects and patients with white coat and established hypertension. The study involved prospective comparison of office blood pressure, daytime ambulatory blood pressure, and urinary albumin excretion in consecutive patients (n = 284) who were selected from general practice with newly diagnosed mild to moderate hypertension before the institution of pharmacologic antihypertensive therapy. All patients had a diastolic office blood pressure above 90 mm Hg; 173 had a consistently elevated diastolic blood pressure (established hypertension), and 111 had an average daytime ambulatory blood pressure below 90 mm Hg (white coat hypertension). A sample of 127 subjects drawn from the Danish national register served as a normotensive control group. The main outcome measure was the ratio of early morning urinary albumin to creatinine. This ratio differed significantly among the three groups, being (on a molar basis) 21 +/- 69 x 10(-6) in the normotensive subjects, 22 +/- 39 x 10(-6) in the white coat hypertensive patients, and 51 +/- 177 x 10(-6) in patients with established hypertension. The difference remained significant after correction for covariables. The ratio of early morning urinary albumin to creatinine was weakly but significantly correlated to blood pressure, was more pronounced for ambulatory than for office measurements, was more pronounced for systolic than for diastolic pressure, and was more pronounced for hypertensive than for normotensive individuals. The ratio was as reproducible a measure as 24-hour albumin excretion. We conclude that white coat hypertensive patients have less renal involvement than patients with established hypertension but more than a normotensive control group.

Epidemiology of microalbuminuria in the general population

Microalbuminuria in the general population is associated with recognized risk factors for cardiovascular disease such as hypertension, hyperglycemia, hyperinsulinemia, and hyperlipidemia; and it is an independent predictor of subsequent cardiovascular mortality in hypertensive, diabetic, and elderly populations. Although different methods have been used for measuring and expressing urinary albumin excretion and a variety of cutoff levels have been used for defining microalbuminuria, prevalence of microalbuminuria appears to be higher in non-Europeans (8%-28%) than in Europeans (2%-10%). However, because of the large within-individual variability of urinary albumin excretion and the relatively low prevalence of microalbuminuria, large studies are required to detect statistically significant associations between albuminuria and cardiovascular risk factors. Evidence presented here supports the proposition that microalbuminuria represents a marker of cardiovascular disease risk in nondiabetic individuals as well as diabetic individuals. Moreover, because of a high sensitivity of the test and because albuminuria is a concomitant of many forms of renal disease, microalbuminuria also has a role in detecting patients with renal involvement associated with essential hypertension, lupus erythematosus, women with pre-eclampsia, and subjects with unsuspected primary and secondary nephropathies.

Occupational hydrocarbon exposure and chronic nephropathy

This review aims at discussing the questions raised by the hydrocarbon-related chronic nephropathy and its possible consequence, the hydrocarbon-related chronic renal failure. It has been attempted to adopt the point of view of the clinician. Therefore, the most important part of the review is devoted to a presentation and an analysis of the available data on humans. The main features of the available studies on human subjects are presented, their conclusions discussed in the light of the possible methodological flaws, and practical conclusions drawn. After a discussion of the main difficulties encountered for selecting the suitable exposure indicator, the studies are discussed in order of decreasing quality of the study design (cohort, case-control, cross-sectional studies, and the case reports). It is concluded that a great deal of controversies about chronic hydrocarbon-related nephropathy is explained by differences in the study design and that hydrocarbon-induced nephropathy is probably more than a mere hypothesis, although a causal relationship has not yet been proven. Finally, some practical consequences for dealing with a hydrocarbon-exposed patient diagnosed with a kidney disease and the need for further research are discussed.

Salt sensitivity in hypertension. Renal and cardiovascular implications

The mechanisms responsible for the increase in blood pressure response to high salt intake in salt-sensitive patients with essential hypertension are complex and only partially understood. A complex interaction between neuroendocrine factors and the kidney may underlie the propensity for such patients to retain salt and develop salt-dependent hypertension. The possible role of vasodilator and natriuretic agents, such as the prostaglandins, endothelium-derived relaxing factor, atrial natriuretic factor, and kinin-kallikrein system, requires further investigation. An association between salt sensitivity and a greater propensity to develop renal failure has been described in certain groups of hypertensive patients, such as blacks, the elderly, and those with diabetes mellitus. Salt-sensitive patients with essential hypertension manifest a deranged renal hemodynamic adaptation to a high dietary salt intake. During a low salt diet, salt-sensitive and salt-resistant patients have similar mean arterial pressure, glomerular filtration rate, effective renal plasma flow, and filtration fraction. On the other hand, during a high salt intake glomerular filtration rate does not change in either group, and effective renal blood flow increases in salt-resistant but decreases in salt-sensitive patients; filtration fraction and glomerular capillary pressure decrease in salt-resistant but increase in salt-sensitive patients. Salt-sensitive patients are also more likely than salt-resistant patients to manifest left ventricular hypertrophy, microalbuminuria, and metabolic abnormalities that may predispose them to cardiovascular diseases. In conclusion, salt sensitivity in hypertension is associated with substantial renal, hemodynamic, and metabolic abnormalities that may enhance the risk of cardiovascular and renal morbidity.

Prognostic value of urinary albumin excretion rate and other risk factors in elderly diabetic patients and non-diabetic control subjects surviving the first 5 years after assessment

In 1981-1982 urinary albumin excretion rates were determined in 211 diabetic and 216 non-diabetic subjects aged 60-74 years. By April 1992 122 diabetic and 58 non-diabetic probands had died. Dividing the two study populations at an albumin excretion rate of 15 micrograms/min showed that 69.3% of diabetic subjects with values at or above the limit, and 49.9% of those with values below (log rank test p = 0.0082) had died. The corresponding values for non-diabetic subjects were 44.4% and 21.0%, respectively (log rank test p = 0.0002). In single factor log rank tests ischaemic heart disease and a low value of HDL were also predictive of death in the diabetic population during a 10-11-year observation period. In the non-diabetic population ischaemic heart disease, hypertension, and a serum creatinine level above the median value were predictive. In further log rank analyses probands dying during the first years, (e.g. the first 2 years) were removed from the calculations. The prognostic value of the above-mentioned factors diminished with time. In a Cox Regression analysis we found that the predictive value of urinary albumin excretion rate to mortality had disappeared when subjects who had died during the first 5 years were removed from the analysis, whereas HDL in the diabetic patients and blood pressure and serum creatinine in non-diabetic subjects were still of significant predictive value. We therefore conclude that urinary albumin excretion rate is a more short-term predictor of mortality than previously thought, in contrast to HDL, hypertension and serum creatinine.

Determinants of end-stage renal disease in Pima Indians with type 2 (non-insulin-dependent) diabetes mellitus and proteinuria

To identify factors related to the development of end-stage renal disease after the onset of proteinuria, its incidence was determined in 364 Pima Indians aged 35 years or older with Type 2 (non-insulin-dependent) diabetes mellitus and proteinuria (protein-to-creatinine ratio > or = 0.5 g/g). Of these 364 subjects, 95 (36 men, 59 women) developed end-stage renal disease. The cumulative incidence was 40% 10 years after and 61% 15 years after the onset of proteinuria. The incidence of end-stage renal disease was significantly related to the duration of diabetes, the duration of proteinuria, higher 2-h plasma glucose concentration, type of diabetes treatment, and the presence of retinopathy at the time of recognition of the proteinuria, but not to age, sex, or blood pressure. Duration of proteinuria influenced the risk of end-stage renal disease, contingent, however, upon the duration of diabetes at the onset of proteinuria. The higher cumulative incidence of end-stage renal disease 15 years after the onset of proteinuria in Pima Indians (61%) than in Caucasians from Rochester, Minnesota (17%) may be attributable, in part, to the younger age of onset of Type 2 diabetes in Pima Indians than in Caucasians, to ethnic differences in susceptibility to renal disease, or to lower death rates among the Pima Indians from competing causes of death, such as coronary heart disease.

Albuminuria in aborigines and Europids of south-eastern Australia

OBJECTIVE

To determine the prevalence of albuminuria in Aborigines and Australians of European descent (Europids), as part of an epidemiological study of glucose intolerance and cardiovascular risk factors based in country towns of south-eastern Australia.

DESIGN

Population-based cross-sectional study, with Aborigines and Europids of south-eastern Australia as the reference populations.

METHOD

Random urine samples were collected from people aged > or = 35 years, and tested with Albuscreen (a test kit sensitive to urinary albumin concentrations of 0.03 g/L) and two other methods in the field. The samples were later analysed for the calculation of urinary albumin:creatinine ratios, which were then categorised according to cut-off points for abnormal renal function that have been proposed in the literature.

RESULTS

Three hundred and six Aborigines and 553 Europids participated, with response rates of 90% and 94% respectively. According to Albuscreen, albuminuria was more common in Aborigines than in Europids. In men, 36% (95% confidence interval [CI], 20%-52%) of Aborigines exceeded the albumin concentration of 0.03 g/L, compared with 14% (CI, 9%-19%) of Europids (P < 0.01); in women, 39% (CI, 27%-51%) of Aborigines exceeded 0.03 g/L, compared with 18% (CI, 12%-24%) of Europids (P < 0.01). Sixty-one per cent (CI, 44%-78%) of Aboriginal men had a urinary albumin:creatinine ratio of > or = 1.30 mg/mmol, compared with 12% (CI, 7%-17%) of Europid men (P < 0.01); 56% (CI, 44%-68%) of Aboriginal women exceeded this cut-off point, compared with 23% (CI, 16%-30%) of Europid women (P < 0.01).

CONCLUSION

A higher prevalence of renal disease in the Aboriginal population of south-eastern Australia is expected. Risk factors for renal disease in Aborigines throughout Australia require elucidation.

Microalbuminuria and coronary heart disease in non-diabetics

Microalbuminuria (or urinary albumin excretion rates (AER) above normal limits) is associated with coronary heart disease (CHD) particularly in diabetics. To determine the sensitivity and specificity of AER for CHD in a non-diabetic population we prospectively studied 115 consecutive patients undergoing coronary angiography and 66 undergoing exercise electrocardiography (ECG). There was no relationship between AER and the severity of CHD determined by angiography (Gensini-scored). While microalbuminuria (AER > 20 micrograms/minute) was 91% specific it had low sensitivity (12%). Microalbuminuria is not a sensitive indicator of CHD in a non-diabetic population.

Fibrinogen and the albumin-globulin ratio in recurrent stroke

BACKGROUND AND PURPOSE

In following patients initially recruited for a cross-sectional study of blood viscosity in ischemic cerebrovascular disease, it was noted that those having a low albumin-globulin ratio appeared to experience the majority of subsequent vascular events. Accordingly, a prospective study in which subjects were assigned to a high or low albumin-globulin cohort was undertaken to examine the relation between a low albumin-globulin ratio, the presence of clinical risk factors for stroke, and the occurrence of subsequent stroke, myocardial infarction, or vascular death.

METHODS

Three groups of subjects were followed for an average of 1.5 +/- 0.8 years to ascertain vascular end points. Group 1 consisted of 126 patients with acute ischemic stroke; group 2 included 109 subjects matched with group 1 for age, medications, and recognized clinical risk factors for stroke; and group 3 was composed of 84 healthy volunteers, matched for age with groups 1 and 2. The median albumin-globulin ratio for group 1 at enrollment, 1.45, was used to dichotomize patients into two cohorts: all subjects with an albumin-globulin ratio of 1.45 or less were assigned to the "low" albumin-globulin cohort; those whose ratio was greater than 1.45 were assigned to the "high" albumin-globulin cohort. The occurrence of vascular end points was verified during subsequent hospitalizations and outpatient clinic visits and by telephone interviews of patients and providers.

RESULTS

A total of 51 vascular events occurred, including 39 in group 1, 8 in group 2, and 4 in group 3. Subjects in either group 1 or 2 who were in the low albumin-globulin cohort had at least double the risk for a subsequent vascular event compared with their counterparts in the high albumin-globulin cohort (P < .01 and P < .03, respectively). In comparison with the high albumin-globulin cohort, significantly more patients in the low albumin-globulin cohort in group 1 had a history of prior stroke (P < .03). When groups 1 and 2 were combined, both a low albumin-globulin ratio and diabetes had a significant independent association with increased risk for subsequent vascular events in a Cox proportional-hazards model (P < .01 and P < .03, respectively).

CONCLUSIONS

The results of this study indicate that significantly increased risk for subsequent vascular events in stroke patients and in subjects with clinical risk factors for stroke is associated with a shift in the concentrations of blood proteins to a prothrombotic environment characterized by lower levels of albumin and an increased concentration of globulins and fibrinogen.

Hemodynamic alterations and urinary albumin excretion in patients with essential hypertension

Salt-sensitive animals as well as patients with essential hypertension appear to have a greater propensity to develop renal disease as a consequence of hypertension. They also manifest an abnormal renal hemodynamic adaptation to changes in dietary sodium intake and blood pressure. This suggests that the two may be related. Some patients with essential hypertension manifest an increase in urinary albumin excretion (UAE). It is uncertain whether this is more common in salt-sensitive patients and whether it represents a marker for progressive renal disease. The effect of antihypertensive agents on UAE varies substantially depending on the agent used, and it is not necessarily related to the antihypertensive action. Whether antihypertensive agents that more effectively reduce UAE may also result in greater renal protective effects remains to be established.

Isradipine decreases exercise-induced albuminuria in patients with essential hypertension

The aim of our study was to investigate the effects of exercise on albuminuria and blood pressure in patients with essential hypertension, and the short-term effect of the calcium channel blocker isradipine on exercise-induced albuminuria (UAE) and blood pressure in the same patients. Ten patients (7 males, 3 females) with essential hypertension were admitted to the study. The mean age was 54 +/- 2.7 years and the mean body mass index was 27 +/- 1 kg/m2. Patients performed two physical exercise tests on a cycloergometer. Workload was increased by 30 watts every 2 min until 90% of the theoretical maximal heart rate was achieved. This workload was maintained for 5 min. Samples for albuminuria assay were collected at the end of exercise and 1 h after exercise. The first physical exercise test was performed after 15 days of placebo washout; the second exercise was performed after 10 days of therapy with isradipine 5 mg once daily p.o. After 10 days of therapy with isradipine, UAE immediately after (31 +/- 8.3 micrograms/min) and 1 h after exercise (31.5 +/- 7.3 micrograms/min) were significantly (p < 0.05) lower as compared to the values found after placebo (37.1 +/- 9.3 micrograms/min; 43.5 +/- 9.9 micrograms/min). Our data show that short-term administration of the calcium channel blocker isradipine is able to cause a concomitant significant decrease in exercise-induced pressor and albuminuric response in patients with essential hypertension. The finding that short-term calcium channel blockade can reduce exercise-induced albuminuria in essential hypertensive patients suggests that progression of nephropathy in this early phase could be slowed by isradipine in these patients.

A comparative study of lisinopril and atenolol on low degree urinary albumin excretion, renal function and haemodynamics in uncomplicated, primary hypertension

The presence of slightly increased urinary albumin excretion (UAE), even at levels well below levels detectable by an ordinary dipstick, has been suggested as a predictor of cardiovascular morbidity and as a reflection of the degree of overall vascular permeability. The aim of the present investigation was to study the effects of two different antihypertensive drug regimens, an ACE inhibitor and a beta-adrenoceptor antagonist, on the low UAE rate observed in subjects with uncomplicated, mild to moderate primary hypertension. After a 4-week placebo run-in period, 49 patients (mean age 54 y) were randomly assigned in a double blind manner either to further 4 weeks on placebo (P, n = 15), 8 weeks on lisinopril (L, n = 17; 20 mg/40 mg o.d.) or 8 weeks on atenolol (A, n = 17; 50 mg/100 mg o.d.). The 24-h UAE was measured every second week. At entry and after 4 weeks the glomerular filtration rate and the renal plasma flow were measured. Both drugs lowered blood pressure (BP) to a similar extent after 4 and 8 weeks of treatment; the blood pressures were 160/106 (P), 159/104 (L) and 154/103 (A) at entry, and 133/83 (L) and 134/87 (A) at the end of the study after 8 weeks. On entry the 24-h UAE in all patients ranged from 4 to 49 mg (mean 14.1 mg), and it did not differ significantly between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Microalbuminuria in patients with essential hypertension: effects of several antihypertensive drugs

PURPOSE

Microalbuminuria can be present in 10% to 40% of patients with essential hypertension and is associated with an increased incidence of cardiovascular events. The effect of commonly used antihypertensive agents on urinary albumin excretion (UAE) has not been well established. The aim of this study was to evaluate the effects of a converting enzyme inhibitor, a calcium channel blocker, a beta blocker, and a diuretic on UAE and on creatinine clearance in patients with mild to moderate hypertension.

PATIENTS AND METHODS

We prospectively measured UAE prior to and 4 and 8 weeks after treatment with enalapril, nitrendipine, atenolol, or a diuretic in 48 patients with essential hypertension and microalbuminuria.

RESULTS

All these agents were equally effective in reducing arterial pressure. However, enalapril but not the other agents significantly decreased UAE.

CONCLUSION

Eight weeks of therapy with enalapril may reduce UAE in patients with mild to moderate essential hypertension, whereas other agents, such as nitrendipine, atenolol, or diuretics, had no measurable effect on UAE. The clinical and prognostic significance of these observations remains to be established.

Natural history of chronic proteinuria complicating pregnancy

OBJECTIVE

Although the significance of proteinuria is well-documented for pregnancy complicated by preeclampsia or diabetes, protein excretion of up to 300 mg per day is considered normal for uncomplicated pregnancy. Our purpose was to determine the significance of otherwise "asymptomatic" proteinuria identified during pregnancy.

STUDY DESIGN

We reviewed the perinatal outcome of 65 pregnancies in 53 women with the following criteria: (1) proteinuria exceeding 500 mg per day, (2) no previously known renal disease, (3) no reversible renal dysfunction, and (4) no evidence for preeclampsia at discovery.

RESULTS

Renal insufficiency coexisted in 62% of women, and 40% had chronic hypertension. Excluding 8 abortions, 53 (93%) of 57 pregnancies resulted in live infants; 45% of infants were delivered preterm and 23% had growth retardation. Of these 57 women, 62% demonstrated clinical evidence compatible with superimposed preeclampsia, and although the incidence of preeclampsia was increased with isolated proteinuria (29%), it was increased even more when there was associated chronic hypertension (incidence 100%) or renal insufficiency (incidence 58%). All 21 women who eventually underwent renal biopsy had histologic evidence of renal disease. To date, with only a limited follow-up of these 53 women, 11 (20%) have progressed to end-stage renal disease.

CONCLUSION

"Asymptomatic" proteinuria is associated with a number of adverse pregnancy outcomes and serious long-term maternal morbidity.

Comments on the clinical impact of hypertension in type I diabetes

In type I diabetes, the quality of life and, in essence, the long-term prognosis or life expectancy of the patient are invariably related to the manifestation of untoward complications. Increased arterial blood pressure (hypertension) has a great influence in these complications. Cumulative evidence has shown that proteinuric type I diabetic patients are easily susceptible to hypertension and its accompanying sequelae. The debilitating effects of hypertension on the progressive development of diabetic nephropathy leading to renal dysfunction and mortality in renal transplant patients have been documented. Proliferative retinopathy and cardiovascular lesions are also frequent devastating complications in hypertensive-diabetic patients. The mechanism of sodium/lithium countertransport activity and the genetic predisposition to hypertension require further elucidation.

Eight to nine year mortality in known non-insulin dependent diabetics and controls

Microalbuminuria is known to predict mortality in elderly, non-insulin dependent diabetic individuals. To test whether this is also so when studied prospectively and over a longer period, we followed 228 persons with known diabetes mellitus and an age and sex matched, non-diabetic cohort for eight to nine years. Both cohorts were found during a population screening in 1981-1982 of 5292 citizens aged 60 to 74 years. At ascertainment extensive clinical and biochemical examinations including determination of urinary albumin were carried out. At May 15, 1990 111 diabetic and 46 non-diabetics had died (P less than 0.0001). In the diabetic cohort the median value of urinary albumin excretion (UAE) was 17.40 micrograms/min. In the group with values at or above 17.40 micrograms/min 62 died, compared with 40 deaths in the group with values below (P = 0.003). In the non-diabetic cohort the median UAE value was 7.52 micrograms/min. In the upper group 26 died, in the lower 15 (P = 0.05). Cox regression analyses showed coefficients of regression for ln(UAE) of 0.333 (P less than 0.001) for the diabetic group and 0.236 (P = 0.048) for the non-diabetic group. In the Cox model for the diabetics, ischemic heart disease was also of independent significance to mortality. The final model for the non-diabetics included hypertension and sex as significant variables. It is concluded that in a prospective study of elderly diabetics urinary albumin excretion rate is the best prognostic factor for long-term mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Microalbuminuria in systemic sclerosis

A prospective study was performed to determine urinary albumin excretion in a group of 28 patients with systemic sclerosis. At the initial screen one patient had proteinuria and three had microalbuminuria. One year later these abnormalities persisted and in two of of the patients serum creatinine had significantly increased. In addition, a further three patients had developed microalbuminuria. In a control group of 10 patients with primary Raynaud's disease none had microalbuminuria. In a second control group of 16 patients with unrelated skin diseases one patient had microalbuminuria and one proteinuria, but both these patients had a history of hypertension. It is concluded that microalbuminuria is more common in patients with systemic sclerosis than in patients of equivalent age with other dermatological conditions but no vascular disease.

Microalbuminuria and associated cardiovascular risk factors in the community

The prevalence of microalbuminuria and relationship to cardiovascular risk factors was examined in a cross-sectional community survey of cardiovascular risk factors. Microalbuminuria (when classified as albumin concentration greater than 20 micrograms/ml) was present in 6.3% of subjects but in conjunction with an albumin/creatinine ratio greater than 3.5 in only 2.2%. Diastolic blood pressure, prevalence of abnormal electrocardiographs, and to a lesser extent systolic blood pressure and fibrinogen concentration, were greater in those with albuminuria concentrations greater than 20 micrograms/ml. The strongest positive univariate correlates of albumin/creatinine ratios in those with detectable albuminuria were age, fibrinogen, blood pressure, total- and low density lipoprotein-(LDL) cholesterol, apo B and alcohol intake, whereas fasting insulin and insulin resistance were inversely correlated. Multiple regression analysis revealed that age, gender, systolic blood pressure and insulin resistance independently accounted for 37% of the variability in albumin/creatinine ratios. When those 10 subjects with microalbuminuria and albumin/creatinine ratios greater than 3.5 were matched with 20 with normoalbuminuria for age, gender and body mass index, the microalbuminuric subjects had significantly lower LDL cholesterol/apo B ratios and a tendency to lower high density lipoprotein (HDL) cholesterol and HDL cholesterol/apo A1 ratios. Microalbuminuria is uncommon in the general population, and is related to ageing, blood pressure and other vascular risk factors. It may reflect the presence of established cardiovascular disease.

Calcium antagonism in essential hypertension: effect on renal haemodynamics and microalbuminuria

Sixteen middle-aged men with primary hypertension were treated with the calcium antagonist isradipine over a 9-week period in a randomized, placebo-controlled, double-blind cross-over manner. At the end of the intervention period the urinary albumin excretion rate, systemic and renal haemodynamics, haemorheological properties of blood and plasma concentrations of atrial natriuretic peptide, noradrenaline and peripheral renin activity were determined. Treatment with isradipine resulted in a substantial reduction in blood pressure due to a reduction in peripheral resistance. The mean albumin excretion rate was not influenced by the isradipine treatment. In a multivariate analysis, changes in the urinary albumin excretion rate were only related to changes in blood pressure.

Assessment of intermittent claudication by quantitation of exercise-induced microalbuminuria

Urinary albumin excretion rates, expressed as albumin-creatinine ratios (ACR, mg/mmol) were measured before and after exercise in 23 claudicants and 10 controls. The mean (range) resting ACRs in the claudicants and controls were 4.42 (0.2-34.6) and 0.77 (0.3-2.8) respectively (P less than 0.001). ACR increased after exercise by a mean of 153% in claudicants to 9.7 (0.2-48.1; P less than 0.001) with no change in controls, 0.79 (0.2-2.1). In patients with claudication there was a positive correlation between ankle pressure recovery time and the relative increase in ACR after exercise (r = 0.64, P less than 0.01). The post-exercise increase in ACR was reduced in all nine patients who underwent bypass surgery. Measurement of ACR after exercise appears to be related to severity of muscle ischaemia and may assist in the assessment of patients with intermittent claudication.

Effect of surgery on the systemic inflammatory response to intermittent claudication

The hypothesis that intermittent claudication initiates a systemic inflammatory response was investigated by studying the effect of exercise on markers of neutrophil activation and vascular permeability in 25 claudicants and 10 controls. Urinary albumin excretion, previously demonstrated to reflect vascular permeability, increased significantly after exercise in claudicants and was associated with decreased neutrophil filterability and increased serum lysozyme activity. No similar exercise-induced changes were seen in controls or in claudicants after successful arterial bypass surgery. These results suggest that intermittent claudication is associated with potentially deleterious systemic manifestations that are surgically reversible.

Microalbuminuria as predictor of increased mortality in elderly people

OBJECTIVE

Correlation of the urinary albumin excretion rate and the risk of death among elderly subjects.

DESIGN

216 Subjects aged 60-74 whose urinary albumin excretion rate had been determined were followed up 62-83 months later.

SETTING

Municipality of Fredericia, Denmark.

SUBJECTS

223 People who had been selected as control subjects for diabetics found during a systematic screening for diabetes of all people aged 60-74 living in the municipality of Fredericia, Denmark. Of these subjects, 216 had an extensive clinical and biochemical examination within a few weeks of selection.

MAIN OUTCOME MEASURE

Death.

RESULTS

The median urinary albumin excretion rate was 7.52 micrograms/min. Eight of those with a rate below the median died compared with 23 with a rate equal to or greater than the median (p = 0.0078). The median albumin excretion rate in the 31 who died was 15.00 micrograms/min. Cardiovascular disease was the most common cause of death in both groups. A multivariate regression analysis of survival data was performed using the proportional hazards model. Besides albumin excretion rate, male sex, serum creatinine concentration, and hypertension were found to be of prognostic value.

CONCLUSIONS

The association between the albumin excretion rate and mortality that has been described in recent years in patients with diabetes mellitus may be present in elderly people in general, even when other known risk factors are taken into account.

Albuminuria reflects widespread vascular damage. The Steno hypothesis

Albuminuria in Type 1 (insulin-dependent) diabetes is not only an indication of renal disease, but a new, independent risk-marker of proliferative retinopathy and macroangiopathy. The coincidence of generalised vascular dysfunction and albuminuria, advanced mesangial expansion, proliferative retinopathy, and severe macroangiopathy suggests a common cause of albuminuria and the severe renal and extrarenal complications associated with it. Enzymes involved in the metabolism of anionic components of the extracellular matrix (e.g. heparan sulphate proteoglycan) vulnerable to hyperglycaemia, seem to constitute the primary cause of albuminuria and the associated complications. Genetic polymorphism of such enzymes is possibly the main reason for variation in susceptibility.

Preclinical detection of nephrotoxicity: description of the tests and appraisal of their health significance

The prevention of renal diseases induced by chemicals requires the use of tests with which adverse renal effects can be detected at a stage when removal from exposure to the offending agent(s) may lead to complete recovery or may at least prevent an accelerated decline in renal function. The screening tests used in clinical medicine for assessing the functional integrity of the kidney are not sufficiently sensitive to attain this objective. In this review, we describe the tests currently available for detecting incipient renal damage and attempt to assess their health significance. A minimal battery of tests is recommended for the detection of groups in industry or in the general population who are at risk. If an increased prevalence of abnormal values for these parameters is found repeatedly in a population, efforts should be made to identify the causal agent(s) and, if possible, to reduce the exposure. Follow-up examinations of subjects identified in this way are also indicated, in order to define the predictive value of the detected changes better.

Microalbuminuria as predictor of vascular disease in non-diabetic subjects. Islington Diabetes Survey

The relation between urinary albumin excretion rate (AER) and vascular disease was studied in 187 subjects aged over 40 selected from 1084 cases attending a diabetic screening project. AER exceeded 20 micrograms/min in 3 of 13 newly diagnosed diabetic subjects (23%) and 16 of 171 non-diabetic subjects (9.4%). There was a weak relation between AER and both systolic and diastolic blood pressures. Coronary heart disease was found in 54 of 164 (32.9%) subjects with AER of 20 micrograms/min or less and in 14 of 19 (74%) with AER above this. Peripheral vascular disease was present in 16 of 165 (9.7%) subjects with AER of 20 micrograms/min or less and 8 of 18 (44%) with a high AER. Logistic regression, including diabetes, impaired glucose tolerance, systolic and diastolic blood pressures, smoking, age, sex, ethnic origin, and body mass index, demonstrated the independence of this relation between AER above 20 micrograms/min and coronary heart disease (odds ratio [OR] 6.38, 95% confidence interval 1.91-21.4) and peripheral vascular disease (OR 7.72, 2.14-27.8). After a mean of 3.6 (SD 0.19) years, 167 subjects (89.3%) were traced. There had been 9 deaths, 3 (2.0%) among 149 subjects with normal AER and 6 (33%) among 18 microalbuminuric subjects (OR 24.33, 5.40-109.7).

Left ventricular hypertrophy among dark- and light-skinned Puerto Rican men: the Puerto Rico Heart Health Program

Racial groups were assessed by determinations of skin color in 3366 urban men in the Puerto Rico Heart Health Program, an epidemiologic study of coronary heart disease in Puerto Rico. These men participated in a comprehensive cardiovascular examination that included assessment of blood pressure, relative weight, physical activity, cigarette smoking, left ventricular hypertrophy (LVH) as determined by ECG, and measurements of skinfold thickness. They were followed for mortality over the next 6 years. Dark-skinned Puerto Rican men had a higher prevalence of both definite and possible LVH-ECG after stratifying by levels of hypertension, relative weight, physical activity, number of cigarettes smoked, and subscapular skinfold thickness. After multivariate adjustment of these factors, the dark-skinned men had approximately twice the prevalence of both definite and possible LVH-ECG as the lighter skinned men. Definite LVH-ECG carries a high mortality risk over the next 6 years as compared to men without definite LVH (fivefold increased risk in lighter skinned and sevenfold increased risk in darker skinned Puerto Rican men).

Prevalence, concentration, and prognostic importance of proteinuria in patients with malignancies

Protein was found significantly more frequently in single urine samples from 504 patients with malignancy (290; 58%) than in 529 controls (119; 22%) (p less than 0.01). Median protein concentration was greater (p less than 0.001) in patients with neoplasia (0.14 g/l) than in controls (0.07 g/l). Actuarial analysis showed a median survival of 4.5 months in patients with proteinuria compared with 10 months in those without (p less than 0.001). The association between proteinuria and shorter survival was statistically significant for patients with gut tumours, lung tumours, and tumours at other sites analysed as a group. Patients with myeloma or urinary tract tumours were not studied. In many patients with malignancy the presence of proteinuria may be associated with a substantially reduced survival time.

Microalbuminuria: a major risk factor in non-insulin-dependent diabetes. A 10-year follow-up study of 503 patients

The impact of microalbuminuria on mortality as well as other risk factors was investigated in a 10-year follow-up study of 503 predominantly non-insulin-dependent diabetic patients of whom 265 had died. Using Cox's regression analysis the prognostic influence of age, sex, age at diagnosis, known diabetes duration, blood pressure, fasting plasma glucose, relative weight, serum creatinine, retinopathy, and treatment was evaluated as well as morning urine albumin concentration (UAC) in four categories, i.e. UAC less than or equal to 15 micrograms/ml (normal), 15 micrograms/ml less than UAC less than or equal to 40 micrograms/ml, 40 micrograms/ml less than UAC less than or equal to 200 micrograms/ml and UAC greater than 200 micrograms/ml. Age, UAC, known duration, and serum creatinine were the only significant risk factors. After correction for the other three independent risk factors, the hazard ratios in the elevated UAC categories relative to the group with UAC less than or equal to 15 micrograms/ml were 1.53 (p = 0.007), 2.28 (p = 0.000002), and 1.82 (p = 0.02). The statistically significant correlations with UAC were: age (r = 0.09, p less than 0.05), duration (r = 0.14, p less than 0.01), systolic blood pressure (r = 0.12, p less than 0.01), serum creatinine (r = 0.33, p less than 0.001), and fasting plasma glucose (r = 0.12, p less than 0.01). Increased UAC was associated also with retinopathy (p = 0.01). Fifty-eight per cent of the deaths were caused by cardiovascular disease or stroke; only 3% died from uraemia. A reinvestigation including blood pressure, fasting plasma glucose, and UAC was made on 208 survivors.