Determination of indoxyl sulfate by spectrofluorimetric method in human plasma through extraction with deep eutectic solvent

A rapid and efficient analytical method was established to quantify indoxyl sulfate (IS) in plasma through extraction technique with a deep eutectic solvent (DES) and spectrofluorimetric method. DES (choline chloride: urea) was mixed with plasma samples for the extraction of IS, followed by the addition of dipotassium hydrogen phosphate (K2HPO4) solution to form an aqueous two-phase system. The fluorescence intensity of IS which was first extracted to the DES-rich-phase and then back-extracted into the salt-rich-phase, was measured by spectrofluorimetric method. Some key factors such as pH, centrifugation speed and time, the volume ratio of DES/salt, and salt concentration were optimized. Under the optimized conditions, the suggested method had a dynamic range between 20 and 160 µg/mL with a coefficient of determination (R2) of 0.99. Precision (relative standard deviation) was less than 15% and accuracy (% relative recovery) was ± 15% at the nominal concentration level. In addition, results showed that IS levels in real samples were higher than 40 µg/mL which was compatible with reported IS levels in end-stage renal disease (ESRD) patients. Overall, all the results reflect the fact that the presented analytical method can potentially be used for the determination of IS in real plasma samples.

Serum indoxyl sulfate predicts adverse cardiovascular events in patients with chronic kidney disease

BACKGROUND/PURPOSE

Indoxyl sulfate (IS) is a protein-binding molecule that exhibits cardiovascular (CV) toxicity. This study determined whether the serum IS level can be used to predict the risk of major adverse CV events (MACEs) in patients with chronic kidney disease (CKD).

METHODS

We studied 147 patients with CKD stage 1-5 over a 3-year follow-up period. IS was measured through mass spectrometry. Patients' demographics were collected and analyzed to predict outcomes by using multivariable Cox regression.

RESULTS

Forty-seven (32.0%) patients had MACEs. IS remained significantly associated with MACEs after multivariable regression analysis. The area under the receiver operating characteristic curve for IS levels was 0.708 (95% confidence interval: 0.618-0.798).

CONCLUSION

IS may have a critical role in the prediction of CV disease in patients with CKD. Further large-scale investigations are warranted and suggested.