Background:We evaluated a new, automated multicapillary zone electrophoresis (CE) instrument (Capillarys ® , 4.51 software version; Sebia) for human serum protein analysis. Methods: With the Capillarys ␤1-␤2؉® reagent set, proteins were separated at 7 kV for 4 min in 15.5 cm ؋ 25 m fused-silica capillaries (n ‫؍‬ 8) at 35.5°C in a pH 10 buffer with online detection at 200 nm. Serum samples with different electrophoretic patterns (n ‫؍‬ 265) or potential interference (n ‫؍‬ 69) were analyzed and compared with agarose gel electrophoresis (AGE; Hydrasys ® -Hyrys ® , Hydragel protein(e) 15/30 ® reagent set; Sebia). Results: CVs were <3.5% for albumin, <11% for ␣ 1 -globulin, <4.1% for ␣ 2 -globulin, <7.4% for ␤-globulin, and <5.8% for ␥-globulin (3 control levels); measured throughput was 60 samples/h. In patients without paraprotein (n ‫؍‬ 116), the median differences between CE and AGE were ؊5.4 g/L for albumin, 4.0 g/L for ␣ 1 -globulin, 0.7 g/L for ␣ 2 -globulin, 0.6 g/L for ␤-globulin (P <0.001 for all fractions), and ؊0.1 g/L for ␥-globulin (not significant). More samples had at least one ␥-migrating peak detected by CE (n ‫؍‬ 135 vs 130; paraprotein detection limit, ϳ0.5-0.7 g/L), but fewer were quantified (n ‫؍‬ 84 vs 91) because of ␥-to ␤-migration shifts. There was a 1.2 g/L median difference between CE and AGE for ␥-migrating paraprotein quantification (n ‫؍‬ 69; P <0.001). Several ultraviolet-absorbing substances (lipid

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Plasma cystatin C, a new marker of glomerular filtration rate (GFR), was prospectively evaluated in surgical intensive care. Cystatin C was measured (immunonephelometry, Dade-Behring) in 10 patients selected to cover a full range of GFR (phase I) and in 28 unselected consecutive patients followed for 5 days post-admission (phase II). Results were compared with (51)Cr-EDTA clearance (phase I only), plasma creatinine (kinetic Jaffe, Roche), 24-h or estimated by Cockcroft and Gault (CG) creatinine clearance (CrCl), and modified diet in renal disease (MDRD)-estimated GFR. In phase I, the highest correlation with(51)Cr-EDTA clearance (22-198 mL/min) was noted for CG CrCl (r(2): 0.883, p<0.001). During phase II follow-up, 24-h CrCl could not be calculated in 25% of daily evaluations. Cystatin C correlated with creatinine (0.856, p<0.0001) and CG CrCl with MDRD GFR (0.926, p<0.0001) in renal failure (10-78 mL/min, n=60). There was a +40% (p<0.001) median difference between cystatin C and creatinine (as a % of upper normal cut-off). Sensitivity/specificity to detect a <80 mL/min CG CrCl was 88/97% for cystatin C vs. 48/100% for creatinine (laboratory cut-off). In patients with normal and stable renal function (n=14), day-to-day intra-individual variation was 7.4% for cystatin C (vs. 10.6% for creatinine). In intensive care unit surgical adult patients, CG CrCl provides an easy and cost-effective estimate of GFR. Superior to creatinine, plasma cystatin C can be measured in selected patients where CG CrCl is known to be inaccurate.

Background: Cystatin C has recently been proposed as an alternative marker of glomerular filtration rate. The diagnostic value of plasma cystatin C for the longitudinal assessment of kidney function after renal transplantation, however, has not been addressed. Methods: Renal function was evaluated in 30 adults receiving renal transplants (46 ± 9 years, mean ± SD) and in 56 healthy controls (38 ± 10 years) using cystatin C. Plasma cystatin C was determined daily starting the day of surgery and for 3 weeks after surgery by an immunonephelometric assay. Results: Plasma concentration significantly decreased during the first week (−44% vs −29% for creatinine). Plasma cystatin C correlated with plasma creatinine (r = 0.741; P &lt;0.0001) and the reciprocal of the creatinine clearance estimated by the Cockcroft-Gault formula (r = 0.882; P &lt;0.001). In all three cases of acute renal impairment, the increase in plasma cystatin C values was more prominent than that of creatinine. Conclusions: Plasma cystatin C is an alternative and accurate marker of allograft function in adult transplant patients. Increased sensitivity compared with creatinine for the detection of acute reduction in glomerular filtration rate allows in some cases a more rapid diagnosis of acute rejection or treatment nephrotoxicity.

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