Smartphone-based point-of-care analyzer for rapid hemoglobin and potassium monitoring in end-stage renal disease and perioperative renal transplantation patients.

This study aimed to develop a smartphone-based analyzer capable of detecting hemoglobin and potassium levels, with clinical validation using a perioperative renal transplant cohort. We implemented azide-methemoglobin and potassium-tetraphenylborate reactions to detect hemoglobin and potassium levels respectively. A smartphone-based system using ambient light sensors and a Phyphox application was used to measure the light intensity changes, with concentrations calculated via calibration curves. 461 hemoglobin measurements and 481 serum potassium test results from 133 patients with end-stage renal disease admitted for pre-transplant evaluation and 51 perioperative renal transplantation patients were analyzed. According to the Bland-Altman analysis, hemoglobin and potassium measurements showing biases of -1.80 g/L (95% limits of agreement: -7.40 to 3.79 g/L) and 0.015 mM (95% limits of agreement: -0.566 to 0.596 mM), respectively. The diagnostic accuracy was acceptable, with overall rates of 86.55% for anemia and 87.73% for dyskalemia. Error grid analysis indicated that 0.40% of hemoglobin values exceeding the ±10.00% limits and 5.81% of potassium values surpassing the ±0.05 mM limits. The analyzer demonstrated remarkable efficiency, achieving median turnaround times of 2 and 29 min for hemoglobin and potassium, respectively. Additionally, we analyzed 221 critical laboratory values from pre-transplant and post-transplant patients. The analysis identified electrolytes and acid-base disorders as the second most frequent pre-transplant and most frequent post-transplant critical alerts and dyskalemia predominated within this category. Similarly, anemia predominated within the pre-transplant and post-transplant hematologic emergencies. In conclusion, the analyzer offers advantages including portability, accuracy, stability and rapidity, and demonstrates significant clinical value for renal transplant recipients.