Micral Test Research Articles

A Comparative Evaluation of Various Methods for Microalbuminuria Screening

Background/Aims: Microalbuminuria is a marker of abnormal vascular response and a predictor of cardiovascular morbidity and mortality. We evaluated a new quantitative office-based method to assess urinary albumin excretion (UAE) and compared it to other established methods. Methods: Spot urine samples from 165 patients were analyzed at a single study site using the HemoCue system, Clinitek Microalbumin, and Chemstrip Micral test, as well as at a central laboratory, where UAE and creatinine levels were measured. The central laboratory UAE values were used as reference. We evaluated the validity of the HemoCue results and compared them to the respective data for the laboratory albumin-to-creatinine ratio (ACR). Additionally, we assessed, diagnostic sensitivity, specificity, and positive and negative predictive values of all four methods, as well as the reproducibility of the HemoCue measurements. Results: Linear regression analysis demonstrated a good correlation for the HemoCue system (y = 0.9978x – 1.0217, R² = 0.904) and ACR (y = 0.0815x + 0.3373, R² = 0.784). Sensitivity and specificity for microalbuminuria diagnosis were 92 and 98% for HemoCue, 73 and 96% for ACR, 100 and 81% for Clinitek Microalbumin, and 70 and 83% for Chemstrip Micral dipstick, respectively. The correlation coefficient of duplicate HemoCue measurements was r = 0.98 (p < 0.001). Conclusions: The HemoCue system for microalbuminuria detection was as accurate and precise as laboratory ACR estimations. Its diagnostic performance was much better than that of widely used dipstick methods.

Reduction of blood pressure and microalbuminuria by intensified antihypertensive treatment in diabetic and non-diabetic hypertensive patients

To examine Blood Pressure (BP) and occurrence of Microalbuminuria (MA) in hypertensive patients with BP > 140/90 mm Hg in general practice and to examine the effect of intensified BP-treatment. A total of 1396 patients (589 with type-2 diabetes) with hypertension were included in an open multicenter GP-study. 52,8% were male, 25% were smokers and the mean BMI was 28,9. We examined systolic and diastolic BP, MA (Micral test), cholesterol and triglycerides and Hgb-A1C. The BP treatment was intensified according to the doctors own choice at visits at 1, 2, 5 and 11 months and the patients were re-examined after 11 months. Target BP was 130/85 mm Hg for D, 140/90 for ND. Mean BP was 161/91 mm Hg at inclusion (156/87 in the diabetic group (D), 164/94 in the non-diabetic group (ND)). At 11 months BP was significantly reduced to 140/82 mm Hg (138/80 in D and 141/84 in ND). 21,3% of D reached a BP < 130/85 mm Hg. In ND 38,7% reached a BP < 140/90 mm Hg. MA was found at inclusion in 31,5% of the patients (41,7% in D, 23,9% in ND). At 11 months the number of patients with MA was significantly reduced to 19,1% (25,7% in D and 14,4% in ND). Se-total cholesterol was 5,45 in D and 5,84 in ND, se-triglycerides 2,25 in D and 1,79 ND and HgbA1C 7,5 in the diabetic group with no significant changes during the 11 months. The highly significant reduction of BP (18/7 mm Hg in D and 23/10 mm Hg in ND) shows that increased attention to the patients BP and intensified antihypertensive treatment results in a much better control of hypertension. MA was often found in the patients with type-2 diabetes. The proportion of patients with MA was reduced by 16% (relatively -38% in D). It is a new finding that 23,8% of hypertensive patients without diabetes have MA, which may be the first sign of incipient nephrosclerosis. In this group it was possible to reduce the occurrence by 9,4% (relatively - 40%) by intensified antihypertensive treatment.

Diagnostic significance of transferrinuria and albumin-specific dipstick testing in primary care patients with elevated office blood pressure

This study assesses the diagnostic accuracy of transferrinuria and an albumin-specific dipstick assay for detection of renal target organ damage (microalbuminuria) in hypertensive patients in a general practice setting. A spot urine sample of 130 nondiabetic patients with elevated office blood pressure readings (>140 and/or 90 mmHg) was investigated by measuring albumin to creatinine ratio (ACR) and transferrin to creatinine ratio (TCR) and by using an albumin-specific dipstick test (Micral). ACR was considered as comparative gold standard. TCR was elevated (>0.19 mg/mmol) in 26 urine samples (20.0% of the test samples). ACR was raised in 29 samples (22.3% of the test samples). Elevated TCR had a sensitivity of 97% and specificity of 91% for detection of microalbuminuria. Positive predicting value for microalbuminuria was 65%; negative predicting value was 99%. Correlation between ACR and TCR was strong (r=0.96). Dipstick testing for albumin was positive in 23 urine samples (17.7% of the test samples), 27 (20.8%) tests were false positive and six (4.6%) false negative. When dipstick was positive, the sensitivity of detecting microalbuminuria was 79%, and specificity 73%. In conclusion, detection of urinary transferrin in nondiabetic patients with hypertension is strongly associated with urinary albumin excretion. However, assessment of TCR does not identify additional patients with microalbuminuria compared to measurement of ACR alone. The semiquantitative Micral test offers a simple and valuable method to screen hypertensive patients for microalbuminuria in a primary care setting.

Screening for microalbuminuria amongst medical students in University of Benin, Nigeria: a pilot study

Microalbuminuria, a predictive tool in both diabetics and hypertensive, is associated with an increase in vascular mortality and morbidity in the healthy population. A cohort of apparently healthy medical students was screened for microalbuminuria using micral test strips. Data on history of hypertension, diabetes mellitus, renal disease and smoking were collected using a self-administered structured questionnaire. Blood pressure and body mass index (BMI) were recorded in all subjects. Microalbuminuria was present in 61% of the students. It was commonly encountered in students who are smokers, have a family history of diabetes mellitus and hypertension. BMI of students with normoalbuminuria was significantly lower than in students with MA (p = 0.012). MA positively correlated with BMI (r = 0.13, p = 0.40). Microalbuminuria is alarmingly prevalent in the group of students studied and may probably predate clinical diagnosis of diabetes mellitus and hypertension. There is need for follow-up and close monitoring of students who have been identified to have MA, as early preventive strategies may be useful. Key Words: Screening, microalbuminuria, healthy students (Jnl Med. & Biomed Res.: 1(2) 2002: 29-33)

Results from the TIP (Tritace in Proteinuria) Intensified Monitoring Project

Albuminuria has been shown to identify patients with an increased cardiovascular risk, and in clinical studies ACE inhibitors reduce the urinary protein excretion. It was the primary aim of this intensified monitoring project to determine whether these results can be reproduced in a clinical practice setting. Micro- (2.7–22.6 mg albumin/mmol creatinine) or macroalbuminuria (>22.6 mg/mmol) was confirmed by a central laboratory in 598 out of 773 patients with hypertension who had albuminuria >50 mg/l on a Micral Test^® II performed by 147 general practitioners. Coronary heart disease (prevalence rates 15% in patients with normalbuminuria, 33% in patients with microalbuminuria, and 40% in patients with macroalbuminuria), heart failure (prevalence rates 19, 29, and 32%, respectively), left ventricular hypertrophy (prevalence rates 30, 42, and 38%, respectively), and peripheral vascular disease (prevalence rates 7, 15, and 20%, respectively) were significantly more common in patients with elevated urinary albumin excretion. 230 patients with microalbuminuria and 202 subjects with macroalbuminuria were treated with the angiotensin-converting enzyme inhibitor ramipril for 6 months. The treatment significantly lowered mean arterial blood pressure (from a median value of 120 mm Hg, quartiles 113–125 mm Hg, to 103 mm Hg, quartiles 100–109 mm Hg) as well as urinary albumin excretion (from a median value of 18 mg/mmol creatinine, quartiles 7.2–54.6 mg/mmol creatinine, to 6.5 mg/mmol creatinine, quartiles 1.6–23.1 mg/mmol creatinine). The treatment efficacy was unaffected by age, body mass index, and smoking status. Patients with diabetes mellitus type II and heart failure also had a significant, although less pronounced reduction of albuminuria. In summary, we conclude that ramipril is able to reduce the urinary albumin excretion in a clinical practice setting, as has been shown in clinical studies. However, the treatment response is not completely uniform, as special patient populations seem to be more resistant to therapy.

Association of urinary albumin concentration with casual and ambulatory blood pressure: a similar relationship in normotensive and hypertensive subjects.

The urinary albumin level has been found to be positively correlated with blood pressure in hypertensive patients. To our knowledge, this relationship has not been evaluated in normotensive subjects and compared with that in hypertensives using casual and ambulatory blood pressure measurements. In this cross-sectional study, a cohort of 234 normotensive and hypertensive participants wore an ambulatory blood pressure monitor for 24 h, standardized casual blood pressure measurements being taken. The urinary albumin concentration was determined by the dipstick Micral Test. The bivariate and multivariate relationship between urinary albumin concentration and demographic and blood pressure measures was investigated using correlational and regression analyses. The prevalence of microalbuminuria was significantly greater in the hypertensive than normotensive participants. The urinary albumin concentration was positively associated with both casual and ambulatory measures of blood pressure in both the normotensive and hypertensive subsamples, stronger correlations being found for systolic blood pressure. The relationship between systolic blood pressure and urinary albumin concentration was similar in the normotensive and hypertensive subsamples. These findings confirm earlier reports of the greater prevalence of microalbuminuria in patients with hypertension than in normotensive participants, as well as those reporting a continuous relationship in hypertensive participants. This study extends prior research to a normotensive subsample, in whom a similar relationship of blood pressure to microalbuminuria, using both ambulatory and casual measures of blood pressure, was found. Future research should investigate the causal direction of this relationship.

Rapid screening test evaluation for microalbuminuria in diabetes mellitus.

Microalbuminuria predicts clinical nephropathy and cardiovascular disease in diabetes mellitus. This study was undertaken to evaluate a screening microalbuminuria test with the Micral test II dipstick in a general practice setting and compare whether, if three urine samples are tested, any advantage is offered over a testing single sample. Two hundred and eighty diabetic patients attending a primary health care centre were studied. The first morning urine albumin concentration was determined by dipstick over 3 consecutive days. We studied two valuation methods: Method 1. Three-sample method: the test was considered positive if albumin was equal to or above 20 mg/l in at least two of three tests; Method 2. Single-sample method: we selected the third test, i.e. the most recent urine sample; if albumin was equal to or above 20 mg/l it was considered positive. The gold standard was the albumin excretion rate measured by a nephelometric method in a 24-h urine collection. Sensitivity, specificity, predictive values and Kappa coefficient were calculated. The diagnostic performance was assessed by a receiver operating characteristic curve. Microalbuminuria was defined for different thresholds of albumin excretion rate, 15, 20, 25 and 30 microg/min: their frequency was 38, 29, 23 and 18%, respectively. For method 1, the sensitivity of Micral test II oscillated between 70-94% and the specificity between 93-83%. For method 2, the sensitivity oscillated between 64-86%, and the specificity between 88-80%. Both methods had a high diagnostic performance. The Kappa coefficient was 84 and 60% for method 1 and 2, respectively. The Micral test II is a rapid, valid and reliable method for microalbuminuria screening in diabetic patients. It constitutes an important tool for diabetic surveillance in general practice. Although the use of three samples provides better results, the use of a single sample produces acceptable results at a low cost.

The MICRAL test for diabetic microalbuminuria: predictive values as a function of prevalence.

The MICRAL test is an immunospecific dipstick for detection of low concentrations of albumin in urine (microalbuminuria). The test is intended to be used for screening in an ambulatory setting. The utility of the test depends on its ability to accurately predict which patients will be classified as either microalbuminuric or normoalbuminuric by means of a standard laboratory method for determination of albumin in urine. We have analysed data from studies with a total of 2904 samples of urine from diabetic patients. The data are from our own study (190 samples) and from a selected set of 10 publications. The results from standard laboratory measurements of albumin in urine were used as " gold standards". The sensitivity and specificity as calculated from the pooled data were 83.2 and 92.3%, respectively. The predictive values were calculated using simulated changes in the prevalence of microalbuminuria (MAU). At a prevalence of MAU of 1% the predictive value of a negative test is 99.9% but that of a positive test only 9.8%. At a prevalence of MAU of 80% the positive predictive value is 97.7% and the negative predictive value 57.9%. In general, any change in the prevalence will lead to a change in the predictive values. Thus the prevalence of MAU in the given clinical setting is a decisive factor in determining the utility of the MICRAL test.