Title

The prevalence of persistent albuminuria and its associated risk factors in hypertensive patients of Karachi Pakistan.

Date of Award

2007

Document Type

Thesis

Degree Name

Master of Science in Epidemiology & Biostatistics (MSc Epidemiology & Biostats)

Department

Community Health Sciences

Abstract

Kidney failure is a worldwide public health problem, with increasing incidence and prevalence, high costs and poor outcome. Detection and treatment of Chronic kidney disease (CKD), before the stage of kidney failure, is therefore of paramount importance especially in the context of developing countries. Albuminuria is one of' the earliest markers of kidney damage and screening for albuminuria is recommended in patients at increased risk for CKD, including those with hypertension, diabetes, cardiovascular disease and a family history of CKD. Accurate estimation of albuminuria requires timed collection of urine over 24 hour, which is cumbersome in routine clinical practice. An alternative method is detection of albuminuria in spot urine sample, either by albumin concentration alone or albumin-to creatinine ratio, which are relatively easy to obtain in the ambulatory setting. In general, ACR has been shown to have slightly better diagnostic accuracy than UAC alone for detection of albuminuria in many populations. We conducted this study to determine the prevalence of persistent albuminuria, defined as urine albumin concentration of 20mg/L and urine sex-specific albumin-to-creatinine ratio of 20 and 3Omg/gm for males and females respectively persisting for more than 3 months in hypertensive population and to study its associated risk factors. A cohort of hypertensive subjects from community who had been screened once for the presence of microalbuminuria, were studied. Those with microalbuminuria and a proportion of normoalbuminoric subjects were retested after a minimal interval of three months. The evaluation included administration of a questionnaire for potential risk factors, measurement of blood pressure, anthropometry (height, weight), and laboratory tests including serum and urinary creatinine, complete urine analysis in addition to microalbumin detection by Nephelometry. All assessments were performed to a standard protocol that confirmed to the international standards for definitions and measurements. Data was analyzed using appropriate descriptive analysis and univariate and multivariable logistic regression analysis methods. From 1340 hypertensives who were screened initially, 240 (17.9%) had tested positive for microalbuminuria. 72% of 240 microalbuminuric could be reevaluated in the present study. From 1100, one hundred one normoalbuminoric were reevaluated to test the diagnostic accuracy of UAC & ACR. The overall response rate was 83.6% however; respondents and nonrespondents populations were comparable. The prevalence of persistent abnormal albuminuria calculated by urine albumin concentration and albumin-to-creatinine ratio was 9.3% and 8.1%respectively. The mean age of subjects with persistent albuminuria was significantly higher compared to hypertensive normoalbuminuric, 56.4 years versus 53.3 years. There was higher proportion of male subjects in the group with persistent albuminuria than normal albuminuric group (48% vs 34.7%) and the difference reached statistical significance (p=0.003). Positive family history of kidney disease was significantly higher in subjects with persistent albuminuric group (24%), than in control group (5.5%),(P=<0.001). Subjects in the persistent albuminuric group had higher mean Cholesterol level compared to normal group and this reached statistical significance. On regression analysis age, male sex, and positive family history of kidney disease emerged as significant demographic risk factors for persistent albuminuria. Of the measurable variable, progressively higher levels of systolic BP, and serum cholesterol were associated with risk of persistent albuminuria. A significant interaction was found between family history of kidney disease and age (p = 0.058), and which can be translated as with the positive family history of kidney disease the risk for the development of persistent albuminuria considerably increases in the young age [AOR= 15.5 with 95% CI: 7.35, 39.9]. In conclusion, although our findings show that both UAC and ACR are good screening tests, the proportion of estimates of UAC within 15, 30 and 50 % of ACR remains suboptimal. (i.e.23.3%, 34.3% and 48% respectively).This suggests that these tests have good accuracies to detect the presence and absence of albuminuria, but UAC may be limited in its ability to quantify the magnitude of albuminuria.

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