Background
Cystatin C is a key GFR biomarker. Recently, Siemens recalibrated the assay based on certified reference material ERM-DA471/IFCC. The NIH-funded longitudinal chronic kidney disease in ...children (CKiD) study has > 3000 cystatin C measurements based on a pre-IFCC calibrator provided by Siemens. Since cystatin C values for CKiD are now standardized to IFCC certified reference material, it is important to relate the IFCC-calibrated results to the previous values so that there are no discontinuous results.
Methods
We diluted cystatin C ERM-DA471/IFCC (5.48 mg/L) into buffer and compared results with predicted ones. We then updated the cystatin C application on our BN II nephelometer to provide results based on pre-IFCC and IFCC calibrations of CKiD specimens simultaneously. We assayed 51 previously analyzed sera and 62 fresh additional specimens.
Results
The predicted concentrations from the IFCC standard were consistently 17% higher than the measured values using the pre-IFCC calibration (
y
= 1.1686
x
). Similarly, the re-run and fresh sample concentrations were 17% higher via the IFCC calibration than by the pre-IFCC calibration (
y
= 1.168
x
). There was very high reliability in the measurements using the previous calibration for re-run specimens (0.99) and for 33 pristine specimens using IFCC calibration (0.99).
Conclusions
We confirm the recalibration proposed by Siemens. To convert pre-IFCC results to IFCC-calibrated concentrations, the value is multiplied by 1.17. Conversely, one divides IFCC-calibrated results by 1.17 to estimate GFR via previously published pre-IFCC CKiD eGFR equations. For older adolescents, cystatin C has already been standardized and can be directly applied to the CKD-EPI equations.
Previous research has demonstrated that ligands for the gamma subtype of peroxisome proliferator-activated receptors (PPARs) reduce inflammation in two different murine models of colitis. This study ...was designed to examine the potential efficacy of rosiglitazone, a ligand for the gamma subtype of PPARs, as a therapy for active ulcerative colitis.
Fifteen patients with mild to moderately active ulcerative colitis despite therapy with 5-aminosalicylic acid compounds were enrolled in an open-label study of rosiglitazone (4 mg b.i.d. p.o.) for 12 wk. Thirteen of 15 patients were receiving concomitant therapy with corticosteroids and/or immunomodulator medications. Disease activity was measured with the Disease Activity Index.
After 12 wk of therapy, four patients (27%) had achieved clinical remission, of whom three (20%) also had an endoscopic remission. Four additional patients (27%) had a clinical response without achieving remission. Two patients were hospitalized with worsened disease activity, and one patient was withdrawn for nephrotic syndrome.
These data suggest that ligands for the gamma subtype of PPARs may represent a novel therapy for ulcerative colitis. A double blind, placebo-controlled, randomized trial is warranted.
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