Real-time point-of-care total protein measurement with a miniaturized optoelectronic biosensor and fast fluorescence-based assay

Measurement of total protein in urine is key to monitoring kidney health in diabetes. However, most total protein assays are performed using large, expensive laboratory chemistry analyzers that are not amenable to point-of-care analysis or home monitoring and cannot provide real-time readouts. We developed a miniaturized optoelectronic biosensor using a vertical cavity surface-emitting laser (VCSEL), coupled with a fast protein assay based on protein-induced fluorescence enhancement (PIFE), that can dynamically measure protein concentrations in protein-spiked buffer, serum, and urine in seconds with excellent sensitivity (urine LOD = 0.023 g/L, LOQ = 0.075 g/L) and over a broad range of physiologically relevant concentrations. Comparison with gold standard clinical assays and standard fluorimetry tools showed that the sensor can accurately and reliably quantitate total protein in clinical urine samples from patients with diabetes. Our VCSEL biosensor is amenable to integration with miniaturized electronics, which could afford a portable, low-cost, easy-to-use device for sensitive, accurate, and real-time total protein measurements from small biofluid volumes.

Urinary albumin strip assay as a screening test to replace quantitative technology in certain conditions

Background The clinical laboratory plays a crucial role in the diagnosis and monitoring of chronic kidney disease. The quantitative measurement of urine albumin in a spot sample, expressed as ratio per creatinine (ACR) is the most frequently used biomarker for such a purpose. Our aim was to evaluate the diagnostic performances of a strip for measuring ACR for differentiating patients who are candidates for subsequent albumin quantification, and to evaluate the economic effects of its implementation. Methods We systematically measured strip analysis when quantitative urinary albumin was requested. Semiquantitative urinary albumin was measured using a UC-3500 (Sysmex, Kobe, Japan), based on the protein error of a pH indicator. We collected and reviewed all the values of quantified urinary albumin and their corresponding results in ACR strip tests. We calculated the diagnostic indicators for ACR at different albumin and creatinine values using the quantitative ACR measurement as a "gold standard". We also studied the economic effects based on both tests prices (€1.31 for quantitative albumin plus creatinine, and €0.04 for an albumin strip). Results The study included 9148 patients (mean age 63, 46.3% men). The results at different albumin and creatinine cutoffs showed the best performance when 10 mg/L and above 50 mg/dL, respectively. Based on our results, we would have saved 3506 urine albumin and creatinine tests in the study period, corresponding to €4226.94. Conclusions The present study supports the use of the ACR strip test to identify pathological albuminuria values to be measured through quantitative methods. Considerable economic savings are possible.

Screening for chronic kidney disease in a community-based diabetes cohort in rural Guatemala: a cross-sectional study

OBJECTIVE

Screening is a key strategy to address the rising burden of chronic kidney disease (CKD) in low-income and middle-income countries. However, there are few reports regarding the implementation of screening programmes in resource-limited settings. The objectives of this study are to (1) to share programmatic experiences implementing CKD screening in a rural, resource-limited setting and (2) to assess the burden of renal disease in a community-based diabetes programme in rural Guatemala.

DESIGN

Cross-sectional assessment of glomerular filtration rate (GFR) and urine albumin.

SETTING

Central Highlands of Guatemala.

PARTICIPANTS

We enrolled 144 adults with type 2 diabetes in a community-based CKD screening activity carried out by the sponsoring institution.

OUTCOME MEASURES

Prevalence of renal disease and risk of CKD progression using Kidney Disease: Improving Global Outcomes definitions and classifications.

RESULTS

We found that 57% of the sample met GFR and/or albuminuria criteria suggestive of CKD. Over half of the sample had moderate or greater increased risk for CKD progression, including nearly 20% who were classified as high or very high risk. Hypertension was common in the sample (42%), and glycaemic control was suboptimal (mean haemoglobin A1c 9.4%±2.5% at programme enrolment and 8.6%±2.3% at time of CKD screening).

CONCLUSIONS

The high burden of renal disease in our patient sample suggests an imperative to better understand the burden and risk factors of CKD in Guatemala. The implementation details we share reveal the tension between evidence-based CKD screening versus screening that can feasibly be delivered in resource-limited global settings.