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Screening for early diabetic nephropathy: which sample to detect microalbuminuria?
Abstract:
In a study to monitor the acceptability of using a timed overnight urine collection to measure microalbuminuria in a large diabetic population, it was found that only 184 (69.4%) of 265 diabetics returned the urine collection to the hospital laboratory. Three proposals for an initial screening test to predict high risk microalbuminuria were analysed. Proposal I: a random urinary albumin concentration (RAC) greater than 25 micrograms/ml predicts an overnight albumin excretion rate (AER) greater than 30 micrograms/min. In 159 diabetics, the sensitivity of this screening test was 56%, specificity 81%, and predictive value 15%. Proposal II: an albumin concentration greater than 20 micrograms/ml in an early morning urine sample predicts an overnight AER greater than 30 micrograms/min. In 175 diabetics, the sensitivity of this screening test was 86%, specificity 97%, and predictive value 71%. Proposal III: an albumin/creatinine ratio (albumin mg/l creatinine mmol/l) greater than 3.5 in an early morning urine sample predicts an overnight AER greater than 30 micrograms/minute. In 171 diabetics, the sensitivity of this screening test was 100%, specificity 95%, and predictive value 64%. It is concluded that an albumin/creatinine ratio performed on an early morning urine sample brought to the diabetic clinic would be a useful initial screening test to detect an overnight AER greater than 30 micrograms/min.
Insights
A simple early morning urine test using an albumin/creatinine ratio is an effective initial screening tool for detecting microalbuminuria in diabetic patients, improving upon other methods.
Area of Science:
- Nephrology
- Diabetology
- Clinical Chemistry
Background:
- Microalbuminuria is a key indicator of diabetic kidney disease.
- Timed overnight urine collection for albumin excretion rate (AER) is accurate but has low patient compliance.
- Development of a reliable, patient-friendly screening test is needed for early detection.
Purpose of the Study:
- To evaluate the acceptability of timed overnight urine collection for microalbuminuria measurement.
- To assess the predictive accuracy of three proposed screening tests for identifying high-risk microalbuminuria.
Main Methods:
- Compared patient return rates for timed overnight urine collection.
- Analyzed sensitivity, specificity, and predictive value of three screening methods: random urinary albumin concentration (RAC), early morning albumin concentration, and albumin/creatinine ratio (ACR).
- Used overnight albumin excretion rate (AER > 30 micrograms/min) as the gold standard.
Main Results:
- Patient compliance with overnight urine collection was low (69.4%).
- Proposal I (RAC > 25 micrograms/ml) showed low sensitivity (56%) and predictive value (15%).
- Proposal II (early morning albumin > 20 micrograms/ml) demonstrated high sensitivity (86%) and specificity (97%).
- Proposal III (ACR > 3.5) exhibited excellent sensitivity (100%) and specificity (95%), with a predictive value of 64%.
Conclusions:
- Timed overnight urine collection is poorly accepted by diabetic patients.
- An early morning urine albumin/creatinine ratio is a highly sensitive and specific screening test for microalbuminuria.
- The ACR test is a practical and useful initial screening tool for detecting elevated overnight AER in diabetic patients.