Diagnostic Accuracy of Smartphone-Enabled Urinary Albumin-to-Creatinine Ratio Testing

Albuminuria is an important biomarker for detecting chronic kidney disease (CKD), particularly in at-risk individuals. Advances in diagnostic technology have introduced home-use, semiquantitative testing methods such as the FDA-cleared Minuteful Kidney Test (MKT). This study compares the diagnostic accuracy of the MKT to the Beckman Coulter AU 480 analyzer, a standard laboratory quantitative method, for detecting albuminuria in individuals with or at risk for CKD.

Urine samples were obtained from individuals with risk factors for kidney damage. Each sample was analyzed for the urinary albumin-to-creatinine ratio (uACR) using both the MKT and the laboratory standard method. Albuminuria was classified according to KDIGO guidelines: A1 (uACR <30 mg/g, "normal to mildly increased"), A2 (uACR 30-300 mg/g, "moderately increased"), and A3 (uACR >300 mg/g, "severely increased"). Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of MKT were calculated against the laboratory standard.

Out of 615 collected urine samples, 555 met inclusion criteria. Albuminuria (uACR >30 mg/g) was detected in 24.9% of samples using the laboratory method (95% CI: 21.3%-28.5%). The MKT demonstrated a sensitivity of 96.4%, specificity of 84.2%, NPV of 98.6%, and PPV of 66.8%. MKT accurately categorized 85.6% of samples into the KDIGO albuminuria categories A1, A2, and A3, identifying 100% of laboratory-confirmed A3 samples as abnormal.

The MKT shows high sensitivity, exceeding the guideline-required threshold (>85%, P < 0.001), and acceptable specificity for detecting albuminuria in high-risk populations. This device offers the potential to improve CKD detection and management and facilitate early intervention in primary care and community settings, where accurate rule-out capabilities are essential.