Paper-Based Device for Naked Eye Urinary Albumin/Creatinine Ratio Evaluation

Ryuya Hiraoka, Kento Kuwahara, Yun Chiao Wen, Tzung Hai Yen, Yuki Hiruta, Chao Min Cheng, Daniel Citterio

Research output: Contribution to journalArticlepeer-review

44 Citations (Scopus)


This paper introduces the concept of "Drawing-PADs" (Drawing paper-based microfluidic analytical devices) allowing to intuitively evaluate the urinary albumin (Alb) index, a clinically important parameter used for the early detection of renal deficiencies related to diabetes, among others. To enable regular monitoring of the Alb index, a simple examination method suitable for self-diagnosis is highly desirable. The Drawing-PADs rely on the simultaneous naked eye detection of Alb and creatinine (Cre) on a single device according to the distance-based microfluidic PAD (μPAD) approach. The Alb index is visualized by simply drawing a straight line connecting the top of two color-changed assay channel sections (Alb and Cre channels), followed by visually confirming the position of the intercept of the drawn straight line. The semiquantitative Alb index evaluation performed with Drawing-PADs does not require any equipment such as a camera, software, or a color reference chart. The obtained results are independent of the sample volume and are not influenced by changes in the absolute Alb and Cre concentrations caused by urine excretion variations, making spot urine assays possible. Classification of Alb index values according to clinically relevant criteria (normoalbuminuria, microalbuminuria, and macroalbuminuria) is readily achieved within 15 min and has been validated for 15 human urine samples including diabetic patients and healthy volunteers.

Original languageEnglish
Pages (from-to)1110-1118
Number of pages9
JournalACS Sensors
Issue number4
Publication statusPublished - 2020 Apr 24


  • albumin index
  • colorimetry
  • distance-based
  • microfluidic
  • naked eye
  • paper-based analytical device

ASJC Scopus subject areas

  • Bioengineering
  • Instrumentation
  • Process Chemistry and Technology
  • Fluid Flow and Transfer Processes


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