Use of colorimetric test strips for monitoring the effect of hemodialysis on salivary nitrite and uric acid in patients with end-stage renal disease: a proof of principle.

BACKGROUND: Initial screening of potential biomarkers for monitoring dialysis was performed with saliva samples collected from patients with end-stage renal disease (ESRD). A more thorough analysis of the most promising markers identified in the initial screening was conducted with saliva samples acquired at hourly intervals throughout dialysis to monitor analyte concentrations as dialysis progressed. We observed that salivary nitrite (NO(2)(-)) and uric acid (UA) concentrations consistently decreased as dialysis proceeded. METHODS: Solution-based colorimetric-detection chemistries for NO(2)(-) and UA were converted to a test strip format to produce a simple method for semiquantitatively measuring NO(2)(-) and UA concentrations in the clinic or at the patient's home. We assessed the test strips with saliva samples collected from both ESRD patients undergoing dialysis and healthy control volunteers to qualitatively monitor the effect of dialysis on salivary NO(2)(-) and UA. We used computer software to analyze digital images of the resulting test strip color intensities. RESULTS: Test strip measurements showed that mean salivary concentrations of NO(2)(-) and UA were decreased in ESRD patients by 86% and 39%, respectively, compared with 15% and 9% for time-matched controls. Comparison of test strip results with calibrated solution-based assays suggests that the test strips can semiquantitatively measure salivary concentrations of NO(2)(-) and UA. CONCLUSIONS: The colorimetric test strips monitored changes in salivary NO(2)(-) and UA concentrations that occurred in ESRD patients during dialysis. The test strips may prove useful for noninvasively evaluating dialysis progress and may also be useful for monitoring renal disease status.

Microsensor arrays for saliva diagnostics.

Optical fiber microarrays have been used to screen saliva from patients with end-stage renal disease (ESRD) to ascertain the efficacy of dialysis. We have successfully identified markers in saliva that correlate with kidney disease. Standard assay chemistries for these markers have been converted to disposable test strips such that patients may one day be able to monitor their clinical status at home. Details of these developments are described. In addition, saliva from asthma and chronic obstructive pulmonary disease (COPD) patients is being screened for useful diagnostic markers. Our goal is to develop a multiplexed assay for these protein and nucleic acid biomarkers for diagnosing the cause and severity of pulmonary exacerbations, enabling more effective treatment to be administered. These results are reported in the second part of this article.