| 1. |
- Grubb, Anders, et al.
(författare)
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Generation of a new cystatin C-based estimating equation for glomerular filtration rate by use of 7 assays standardized to the international calibrator
- 2014
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 60:7, s. 974-986
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:Many different cystatin C-based equations exist for estimating glomerular filtration rate. Major reasons for this are the previous lack of an international cystatin C calibrator and the nonequivalence of results from different cystatin C assays.METHODS:Use of the recently introduced certified reference material, ERM-DA471/IFCC, and further work to achieve high agreement and equivalence of 7 commercially available cystatin C assays allowed a substantial decrease of the CV of the assays, as defined by their performance in an external quality assessment for clinical laboratory investigations. By use of 2 of these assays and a population of 4690 subjects, with large subpopulations of children and Asian and Caucasian adults, with their GFR determined by either renal or plasma inulin clearance or plasma iohexol clearance, we attempted to produce a virtually assay-independent simple cystatin C-based equation for estimation of GFR.RESULTS:We developed a simple cystatin C-based equation for estimation of GFR comprising only 2 variables, cystatin C concentration and age. No terms for race and sex are required for optimal diagnostic performance. The equation, [Formula: see text] is also biologically oriented, with 1 term for the theoretical renal clearance of small molecules and 1 constant for extrarenal clearance of cystatin C.CONCLUSIONS:A virtually assay-independent simple cystatin C-based and biologically oriented equation for estimation of GFR, without terms for sex and race, was produced.
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| 2. |
- Björk, Jonas, et al.
(författare)
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Accuracy of GFR estimating equations combining standardized cystatin C and creatinine assays: a cross-sectional study in Sweden
- 2015
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Ingår i: Clinical Chemistry and Laboratory Medicine. - : Walter de Gruyter GmbH. - 1434-6621 .- 1437-4331. ; 53:3, s. 403-414
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Tidskriftsartikel (refereegranskat)abstract
- Background: The recently established international cystatin C calibrator makes it possible to develop non-laboratory specific glomerular filtration rate (GFR) estimating (eGFR) equations. This study compares the performance of the arithmetic mean of the revised Lund-Malmo creatinine and CAPA cystatin C equations (MEAN(LM-REV+CAPA)), the arithmetic mean of the Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI) creatinine and cystatin C equations (MEAN(CKD-EPI)), and the composite CKD-EPI equation (CKD-EPICREA+CYSC) with the corresponding single marker equations using internationally standardized calibrators for both cystatin C and creatinine. Methods: The study included 1200 examinations in 1112 adult Swedish patients referred for measurement of GFR (mGFR) 2008-2010 by plasma clearance of iohexol (median 51 mL/min/1.73 m(2)). Bias, precision (interquartile range, IQR) and accuracy (percentage of estimates +/- 30% of mGFR; P-30) were compared. Results: Combined marker equations were unbiased and had higher precision and accuracy than single marker equations. Overall results of MEAN(LM-REV+CAPA)/MEAN(CKD-EPI)/CKD-EPICREA+CYSC were: median bias -2.2%/-0.5%/-1.6%, IQR 9.2/9.2/8.8 mL/min/1.73 m(2), and P-30 91.3%/91.0%/91.1%. The P-30 figures were about 7-14 -percentage points higher than the single marker equations. The combined equations also had a more stable performance across mGFR, age and BMI intervals, generally with P-30 >= 90% and never <80%. Combined equations reached P-30 of 95% when the difference between eGFR(CREA) and eGFR(CYSC) was <10% but decreased to 82% at a difference of >= 40%. Conclusions: Combining cystatin C and creatinine assays improves GFR estimations with P-30 >= 90% in adults. Reporting estimates of both single and combined marker equations in clinical settings makes it possible to assess the validity of the combined equation based on the agreement between the single marker equations.
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| 3. |
- Hansson, Lars-Olof, et al.
(författare)
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Performance evaluation of a turbidimetric cystatin C assay on different high-throughput platforms
- 2010
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Ingår i: Scandinavian Journal of Clinical & Laboratory Investigation. - : Informa UK Limited. - 1502-7686 .- 0036-5513. ; 70:5, s. 347-353
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Tidskriftsartikel (refereegranskat)abstract
- Objective. The goal with this study was to evaluate the analytical performance of a new cystatin C immunoassay (Tina-quant (R) a Cystatin C, Roche Diagnostics GmbH). The evaluation was carried out at four centers according to a standardized protocol. Material and methods. The Tina-quant (R) a Cystatin C is a latex particle-enhanced immunoturbidimetric assay. Roche cobas (R) 6000, MODULAR ANALYTICS SWA and COBAS INTEGRA (R) instruments were included in the study. Method comparison studies were carried out against two turbidimetric methods (Dako Cystatin C, Gentian Cystatin C), and one nephelometric method (Siemens N-Latex Cystatin C). Results. Linearity was proven throughout the measuring range from 0.4 to 8 mg/L. Within-run CVs ranged from 0.7-2.8%, and total CVs from 1.4-4.7 % (concentration range 0.6-3.9 mg/L). Comparable results were obtained with paired serum and Li-heparinate plasma samples. Good agreement was achieved in the comparisons between the Tina-quant (R) a Cystatin C assay and the other commercially available cystatin C assays, two different turbidimetric methods (slope range 0.88-1.04, intercept < 0.17 mg/L, r >= 0.993) and one nephelometric assay (slope range 0.90-1.05, intercept < 0.21 mg/L, r >= 0.986). Conclusions. The Tina-quant (R) a Cystatin C assay was shown to be precise and accurate with proven linearity over the measuring range. Good comparability was obtained with other commercially available assays for the determination of cystatin C. The Tina-quant (R) a Cystatin C assay is very well suited for clinical use on routine clinical chemistry analysers to detect renal dysfunction with a 24 h availability.
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| 4. |
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| 5. |
- Nyman, Ulf, et al.
(författare)
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The revised Lund-Malmo GFR estimating equation outperforms MDRD and CKD-EPI across GFR, age and BMI intervals in a large Swedish population
- 2014
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Ingår i: Clinical Chemistry and Laboratory Medicine. - : Walter de Gruyter GmbH. - 1434-6621 .- 1437-4331. ; 52:6, s. 815-824
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Tidskriftsartikel (refereegranskat)abstract
- Background: The performance of creatinine-based glomerular filtration rate (GFR) estimating equations may vary in subgroups defined by GFR, age and body mass index (BMI). This study compares the performance of the Modification of Diet in Renal Disease (MDRD) study and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations with the revised Lund-Malmo equation (LM Revised), a new equation that can be expected to handle changes in GFR across the life span more accurately. Methods: The study included 3495 examinations in 2847 adult Swedish patients referred for measurement of GFR (mGFR) 2008-2010 by plasma clearance of iohexol (median 52 mL/min/1.73 m(2)). Bias, precision [interquartile range (IQR)] and accuracy [percentage of estimates +/- 10% (P-10) and +/- 30% (P-30) of mGFR] were compared. Results: The overall results of LM Revised/MDRD/CKD-EPI were: median bias 2%/8%/11%, IQR 12/14/14 mL/min/1.73 m(2), P-10 40%/35%/35% and P-30 84%/75%/76%. LM Revised was the most stable equation in terms of bias, precision and accuracy across mGFR, age and BMI intervals irrespective of gender. MDRD and CKD-EPI overestimated mGFR in patients with decreased kidney function, young adults and elderly. All three equations overestimated mGFR and had low accuracy in patients with BMI <20 kg/m(2), most pronounced among men. Conclusions: In settings similar to the investigated cohort LM Revised should be preferred to MDRD and CKD-EPI due to its higher accuracy and more stable performance across GFR, age and BMI intervals.
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| 6. |
- Flodin, Mats, et al.
(författare)
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Evaluation of Dade Behring N Latex Cystatin C reagent on Abbott ci8200
- 2006
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Ingår i: Upsala Journal of Medical Sciences. - 0300-9734 .- 2000-1967. ; 111:2, s. 209-213
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Tidskriftsartikel (refereegranskat)abstract
- Plasma cystatin C has been shown in several studies to be superior to plasma creatinine for estimation of glomerular filtration rate (GFR). Reporting cystatin C results in mL/min using conversion formulas for transforming cystatin C expressed as mg/L to GFR expressed as mL/min has greatly facilitated the clinical use of the marker. At our hospital we have an increasing demand for cystatin C and at present we perform over 1,400 cystatin C analyses a month. The test is available at all hours. This in combination with the volume emphasises the need to have the assay close to the routine chemistry instrument to reduce handling time per test and time to report test results. We have thus evaluated the Dade Behring N Latex Cystatin C assay (Dade Behring, Deerfield, IL, USA) on Architect 68200 (Abbott Laboratories, Abbott Park, IL, USA). The nephelometric method on the ProSpec (Dade Behring) and the turbidimetric method on Architect 68200 showed very good agreement (y = 1.0072x + 0.0042; R-2 = 0.987). Accordingly, running the cystatin C analyses on a chemistry instrument (Architect 68200) would be proper to increase the availability of the analysis and reduce turnaround times.
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| 7. |
- Flodin, Mats, et al.
(författare)
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Variations in assay protocol for the Dako cystatin C method may change patient results by 50% without changing the results for controls
- 2006
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Ingår i: Clinical Chemistry and Laboratory Medicine. - 1434-6621 .- 1437-4331. ; 44:12, s. 1481-1485
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Tidskriftsartikel (refereegranskat)abstract
- Background: Cystatin C is increasingly used as a glomerular filtration marker, but so far only a few companies produce most of the cystatin C reagents suited for turbidimetry or nephelometry use in clinical laboratories. Methods: We studied different protocols for measuring cystatin C on an Architect ci8200 system using cystatin C reagents from Dako (Glostrup, Denmark). The results were compared with those obtained with Dade Behring reagents (Deerfield, IL, USA) on a BN ProSpec system. Results: Differences in assay protocol on the same instrument with the Dako reagent yielded an up to 50% difference in glomerular filtration rate calculated from the cystatin C results when analyzing patient samples, but had no effect on the results for controls. There were also significant differences regarding linearity and kinetics between samples and controls/calibrators. Conclusions: The results indicate different reactivity of the Dako antibodies against calibrators and controls in comparison with patient samples, highlighting the importance of using controls and calibrators that do not differ from patient samples.
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| 8. |
- Hansson, Lars-Olof, et al.
(författare)
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Comparison between Chicken and Rabbit Antibody Based Particle Enhanced Cystatin C Reagents for Immunoturbidimetry
- 2008
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Ingår i: Journal of immunoassay & immunochemistry. - : Informa UK Limited. - 1532-1819 .- 1532-4230. ; 29:1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- We have compared three commercial particle enhanced cystatin C reagents. One of the reagents utilizes chicken antibodies and the other two reagents are rabbit antibody based. We show that the chicken antibody based reagent yields a higher delta absorbance when reacting with the antigen. IgY coupled to latex particles show a strong scatter response even at high antigen concentrations in contrast to the steep decline in scatter previously reported for IgY antibodies in solution. The reagent also showed a low CV for duplicate samples. Laying hens thus seems as an interesting source of antibodies for particle-enhanced immunoassays.
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| 9. |
- Helmersson-Karlqvist, Johanna, et al.
(författare)
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The age related association is more pronounced for cystatin C estimated GFR than for creatinine estimated GFR in primary care patients
- 2013
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Ingår i: Clinical Biochemistry. - : Elsevier BV. - 0009-9120 .- 1873-2933. ; 46:16-17, s. 1761-1763
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Tidskriftsartikel (refereegranskat)abstract
- ObjectivesThere is an age associated change in GFR but this association may be influenced by the method used. The aims of the present study were to assess the association between age and cystatin C and creatinine based glomerular filtration rate estimates in primary care patients, and to determine the proportion of patients with clinically important renal impairment.Materials and methods1552 samples with simultaneous requests for creatinine and cystatin C from 1552 primary care patients in the county of Uppsala, Sweden were analysed. MDRD, CKD-EPI and cystatin C equations were used to calculate glomerular filtration rate (GFR) and the associations between GFR and age were explored.ResultsThe yearly change in cystatin C estimated GFR was 1.24 mL/min/1.73 m2 while the corresponding decline for creatinine estimated GFR was 0.76 mL/min/1.73 m2 for MDRD and 0.99 mL/min/1.73 m2 for CKD-EPI.ConclusionsThe age related association with GFR estimates is smaller for creatinine estimates than for cystatin C estimates. This leads to differences in the number of patients with reduced eGFR detected with the three estimates and the patient treatment will depend on the estimate used. This is not coherent with a good patient care and we thus need to develop new eGFR equations with better agreement between the estimates.
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| 10. |
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