Uncertain clinical utility of contemporary strategies for microalbuminuria testing

Albuminuria screening in children with type 1 diabetes prior to and during the COVID-19 pandemic

BACKGROUND

Albuminuria is an important risk factor for adverse renal and cardiovascular outcomes in type 1 diabetes (T1D). We sought to describe: (1) adherence to albuminuria screening prior to and during the COVID-19 pandemic and (2) occurrence of abnormal urine albumin-creatinine ratio (ACR) tests in children with T1D.

METHODS

This cohort study involved children aged 18 years or younger with T1D followed in the diabetes clinic at a pediatric tertiary center. Data was collected from 2016 to 2020. Adherence was defined by Diabetes Canada (DC) Guidelines for T1D in Children and Adolescents (2018).

RESULTS

Of the 165 children who met DC criteria for screening; 88 (32%) were male and the median age at diagnosis was 5.8 years. Twenty-eight (17%) children had not completed a single ACR test, and 30 (18%) completed all eligible ACR tests. Test completion decreased from 66% in 2019 to 45% in 2020. Of the 345 ACR tests completed, 40 (11%) were abnormal (>2.5 mg/mmol) and 29 abnormal ACR tests (72%) were not repeated.

CONCLUSION

Adherence to albuminuria screening in this pediatric diabetes clinic is suboptimal with deterioration during the COVID-19 pandemic. Patient/physician and program-level strategies to improve adherence will play an important role in quality improvement.

IMPACT

Albuminuria screening is an important part of pediatric diabetes care. In our study, pediatric albuminuria screening adherence was suboptimal at 66% in 2019 and deteriorated during the pandemic to 45% in 2020. Program and patient-level adherence to clinical guidelines and barriers to accessing diabetes care during the pandemic merit further study.

Proteinuria versus albuminuria in chronic kidney disease

Chronic kidney disease (CKD) is defined according to a decrease in the glomerular filtration rate and kidney damage such as proteinuria or albuminuria. Dip-stick proteinuria is only sensitive to albumin and correlates poorly with quantitative 24 h proteinuria, the most commonly used measure in renoprotective randomized controlled clinical trials (RCT). The amount of proteinuria correlates with the efficacy of angiotensin-converting enzyme inhibitors in non-diabetics in RCT. Random urine protein to creatinine ratio (PCR) or albumin to creatinine ratio (ACR) correlates with 24 h urinary excretion. Dip-stick proteinuria correlates poorly with ACR, while PCR correlates reasonably well with ACR. Because of a high analytical variability, efforts are in progress to standardize ACR (but not PCR) measurement. There have been no studies on the direct comparison between proteinuria and albuminuria in terms of utilities (biomarker, surrogate end-point and cost-effectiveness). In this regard, both proteinuria and albuminuria are good biomarkers for cardiovascular events, renal events or mortality. However, there are limitations in RCT regarding the validity of proteinuria or albuminuria as a surrogate end-point. In contrast, measuring proteinuria or albuminuria followed by treatment with angiotensin inhibitors is cost-effective for diabetics, hypertension and aging. CKD guidelines differ in their opinions regarding the choice between ACR and PCR. Based on the current evidence, ACR might be recommended for the diabetics and PCR for the non-diabetics.

Hypertension-based clinical risk strategies for detecting microalbuminuria in diabetes

BACKGROUND

Microalbuminuria screening to identify patients at risk of diabetic nephropathy is widely accepted.

AIM

To investigate whether blood-pressure-based strategies can identify such patients without the need for microalbuminuria testing.

METHODS

Spot urine for albumin/creatinine ratios was performed in all patients over an 18-month period. The performance of four combinations of clinical models, based on existing triggers for anti-hypertensive intervention (prior use and/or existing systolic BP exceeding 140 or 160 mmHg and/or dipstick proteinuria exceeding 1+ or 2+) was evaluated at microalbuminuria thresholds of 3.5 and 10 mg/mmol. The models were ranked 1 to 4, based on their escalating relative strengths in predicting need for intervention.

RESULTS

Of 3748 patients, 1257 (34%) or 739 (20%) exceeded microalbuminuria thresholds of 3.5 or 10 mg/mmol. All four models predicted microalbuminuria risk (areas under ROC curves 0.60-0.77, all p < 0.001). The models (1-4) identified 2220, 2465, 2803 or 2937 for intervention, respectively, irrespective of microalbuminuria status, and missed 368, 232, 194 or 126 at 3.5 mg/mmol and 164, 87, 81 or 45 at 10 mg/mmol.

DISCUSSION

Clinical models using routinely measured parameters reduced the target population for microalbuminuria screening by 60-80%, missing 3-10% of patients with albumin/creatinine ratios exceeding 3.5 mg/mmol or 1-4% of those exceeding 10 mg/mmol.