| 1. |
- Björk, Jonas, et al.
(författare)
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A new tool for predicting the probability of chronic kidney disease from a specific value of estimated GFR.
- 2010
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Ingår i: Scandinavian Journal of Clinical and Laboratory Investigation. - : Informa UK Limited. - 1502-7686 .- 0036-5513. ; Jul 1, s. 327-333
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Objective. To demonstrate how patients' probability of having chronic kidney disease (CKD) stage 3-5 (measured GFR <60 mL/min/1.73 m(2)) can be predicted from a specific value of estimated glomerular filtration rate (eGFR). Material and methods. The probability of CKD stage 3-5 was predicted from a logistic regression model (n = 850) using three different eGFR prediction equations: Lund-Malmö, MDRD and CKD-EPI. Population weighting was used to illustrate how this probability varies in three different populations: original sample (55% true prevalence of CKD stage 3-5), a screening (6.7% prevalence) and a CKD population (84% prevalence). Results. All three eGFR-equations had high classification ability (area under the receiver-operating-characteristic curve = 97%). The probability of CKD stage 3-5 increased with decreasing eGFR, varied substantially among the populations studied and to some extent between the eGFR-equations. Using the Lund-Malmö equation as illustration, the probability of CKD stage 3-5 is > 90% only when eGFR is <38 mL/min/1.73 m(2) in a screening population, whereas it is > 90% already when eGFR is <51 mL/min/1.73 m(2) in a CKD population. Conversely, the probability of CKD stage 3-5 is <10% if eGFR > 59 mL/min/1.73 m(2) in a screening population, whereas it is <10% only when eGFR is > 88 mL/min/1.73 m(2) in a CKD population. Conclusion. Instead of reporting diagnostic accuracy as sensitivity, specificity, and predictive values, actual eGFR supplemented with the probability that it represents a true GFR <60 mL/min/1.73 m(2) may be more valuable for physicians. Clinical (pre-test) probability in the population must be considered when predicting this probability.
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| 2. |
- Björk, Jonas, et al.
(författare)
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A novel method for creatinine adjustment makes the revised Lund-Malmö GFR estimating equation applicable in children
- 2020
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Ingår i: Scandinavian Journal of Clinical and Laboratory Investigation. - : Informa UK Limited. - 0036-5513 .- 1502-7686. ; 80:6, s. 456-463
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to establish creatinine growth curves separately for males and females that can be used to adjust childhood levels of serum creatinine to corresponding adult levels. Linear regression with fractional polynomials of age as independent variable was used to construct creatinine growth curves for a reference cohort (n = 83,157 samples from Belgium and Sweden, age 2-40 years). Adjusted creatinine obtained from the growth curves was used to improve accuracy of estimated glomerular filtration rate (eGFR) based on the Lund-Malmö revised (LMR) equation in children. The LMR equation based on creatinine values adjusted to age 18 years was validated against measured GFR (mGFR) in a separate cohort of 4005 children from four different European countries. Validation metrics included median bias, precision, and accuracy expressed as percentage of estimates within ±30% (P30) of mGFR. Remarkable improvements in bias and accuracy were observed; P30 increased from 56% to 74% after creatinine adjustments in children with mGFR <75 mL/min/1.73 m2 (n = 932), while P30 was relatively unchanged (89-90%) at mGFR ≥75 mL/min/1.73 m2 (n = 3073). The suggested approach with adjusted creatinine makes LMR applicable in children irrespective of their renal function.
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| 3. |
- Björk, Jonas, et al.
(författare)
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Accuracy diagrams : a novel way to illustrate uncertainty of estimated GFR
- 2017
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Ingår i: Scandinavian Journal of Clinical and Laboratory Investigation. - : Informa UK Limited. - 0036-5513 .- 1502-7686. ; 77:3, s. 199-204
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Tidskriftsartikel (refereegranskat)abstract
- Most studies that validate GFR equations present accuracy results stratified by measured GFR (mGFR; diagnostic correctness) or by estimated GFR (eGFR; diagnostic predictiveness) only, without a clear distinction in interpretation. The accuracy of a GFR equation is normally reported in percent (e.g. P30), but is often misinterpreted when stratified by eGFR. The aim of the study was to develop new accuracy measures and diagrams that allow straightforward interpretations and illustrations of the uncertainty in eGFR in clinical practice. We applied quantile regression to the distribution of estimation errors for two creatinine-based GFR equations, LM-REV and CKD-EPI, in a clinical cohort (n = 3495) referred for GFR measurement (plasma clearance of iohexol). Measures of bias and precision and accuracy intervals (AIs) were expressed in mL/min/1.73 m2. Diagrams with AIs were chosen as a novel way to present the error margin in eGFR at a pre-specified certainty level. It was shown that creatinine-based equations are still quite inaccurate in that large estimation errors could not be ruled out with satisfactory certainty. As an example, the 75% AI for the most accurate equation, LM-REV, was approximately ±10 mL/min/1.73 m2 at eGFR = 45 mL/min/1.73 m2, whereas it ranged between −13 and +20 mL/min/1.73 m2 at eGFR = 90 mL/min/1.73 m2. Accuracy intervals presented in diagrams can be used to illustrate the uncertainty of eGFR. Future validation studies should assess the variability in the predictiveness of eGFR across populations and clinical settings using tools and performance measures that are easy to interpret.
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| 4. |
- Björk, Jonas, et al.
(författare)
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Revised equations for estimating glomerular filtration rate based on the Lund-Malmö Study cohort.
- 2011
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Ingår i: Scandinavian Journal of Clinical and Laboratory Investigation. - : Informa UK Limited. - 1502-7686 .- 0036-5513. ; 71, s. 232-239
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Objective. To increase the accuracy of estimated GFR (eGFR) from creatinine overall and at measured GFR ≥90 mL/min per 1.73 m(2) by revising the Lund-Malmö (LM) equations, to elaborate on more complex forms to improve the LM and CKD-EPI equations further, and to assess benefits of adding lean body mass (LBM). Material and methods. Swedish Caucasians (n = 850, 376 women; median 60, range 18-95 years) referred for GFR measurement (plasma iohexol-clearance: median 55, range 5-173 mL/min/1.73 m(2)) constituted the Lund-Malmö Study cohort. Bias, precision, accuracy, expressed as median absolute percentage difference and percentage of estimates ±10% (P(10)) and ±30% (P(30)) of measured GFR, and classification ability with respect to five GFR stages were compared with the original LM, CKD-EPI and MDRD equations. Results. LM Revised overall performed better than LM Original without LBM due to increased accuracy at measured GFR ≥90 mL/min/1.73 m(2). Further extensions of the CKD-EPI or LM equations did not substantially improve overall performance. In particular, the performance of LM Revised at measured GFR ≥90 mL/min/1.73 m(2) could not be improved further without decreasing accuracy and classification ability at lower GFR-levels. Adding LBM to the equations had no strong effect on accuracy. Conclusion. Comparisons with the CKD-EPI and MDRD equations suggest that the LM equations are superior for the present Swedish population, due to markedly higher accuracy of the LM equations at measured GFR <30 mL/min/1.73 m(2). However, the LM equations cannot be recommended for use in general clinical practice until validated in other populations.
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| 5. |
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| 6. |
- Grubb, Anders, et al.
(författare)
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Cystatin C, a marker for successful aging and glomerular filtration rate, is not influenced by inflammation.
- 2011
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Ingår i: Scandinavian Journal of Clinical and Laboratory Investigation. - : Informa UK Limited. - 1502-7686 .- 0036-5513. ; 71, s. 145-149
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Background. The plasma level of cystatin C is a better marker than plasma creatinine for successful aging. It has been assumed that the advantage of cystatin C is not only due to it being a better marker for glomerular filtration rate (GFR) than creatinine, but also because an inflammatory state of a patient induces a raised cystatin C level. However, the observations of an association between cystatin C level and inflammation stem from large cohort studies. The present work concerns the cystatin C levels and degree of inflammation in longitudinal studies of individual subjects without inflammation, who undergo elective surgery. Methods. Cystatin C, creatinine, and the inflammatory markers CRP, serum amyloid A (SAA), haptoglobin and orosomucoid were measured in plasma samples from 35 patients the day before elective surgery and subsequently during seven consecutive days. Results. Twenty patients had CRP-levels below 1 mg/L before surgery and low levels of the additional inflammatory markers. Surgery caused marked inflammation with high peak values of CRP and SAA on the second day after the operation. The cystatin C level did not change significantly during the observation period and did not correlate significantly with the level of any of the four inflammatory markers. The creatinine level was significantly reduced on the first postoperative day but reached the preoperative level towards the end of the observation period. Conclusion. The inflammatory status of a patient does not influence the role of cystatin C as a marker of successful aging, nor of GFR.
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| 7. |
- Grubb, Anders, et al.
(författare)
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Improved estimation of glomerular filtration rate (GFR) by comparison of eGFR(cystatin C) and eGFR(creatinine)
- 2012
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Ingår i: Scandinavian Journal of Clinical & Laboratory Investigation. - : Informa UK Limited. - 1502-7686 .- 0036-5513. ; 72:1, s. 73-77
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Tidskriftsartikel (refereegranskat)abstract
- Objective. GFR-prediction equations based upon cystatin C and creatinine have better diagnostic performance in estimating GFR than equations based upon only one of the two markers. The present work concerns in what way a comparison between separate estimations of GFR based upon cystatin C (eGFR(cystatin C)) or creatinine (eGFR(creatinine)) can be used to evaluate the diagnostic performance of a combined cystatin C-and creatinine-based estimation of GFR. Methods. The difference between eGFR(cystatin C) and eGFR(creatinine) was compared with measured GFR (iohexol clearance) and a combined cystatin C- and creatinine-based estimation of GFR in a Swedish-Caucasian cohort of 857 adult patients. Results. A difference between eGFR(cystatin C) and eGFR(creatinine) of >= 40% indicated a markedly reduced diagnostic performance of the combined cystatin C- and creatinine-based estimation of GFR. Conclusion. Comparison of the agreement between eGFR(cystatin C) and eGFR(creatinine) can be used to evaluate the diagnostic performance of combined cystatin C-and creatinine-based estimations of GFR. If 'threshold values' for discordance are exceeded, it must be considered whether the clinical context requires the use of an invasive gold standard method to measure GFR. In some clinical contexts either creatinine or cystatin C are known to be invalidated as markers of GFR and in these situations the use of only the cystatin C-or the creatinine-based GFR estimate should be considered when the 'threshold values' are exceeded.
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| 8. |
- Leion, Felicia, et al.
(författare)
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Estimating glomerular filtration rate (GFR) in children. The average between a cystatin C- and a creatinine-based equation improves estimation of GFR in both children and adults and enables diagnosing Shrunken Pore Syndrome.
- 2017
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Ingår i: Scandinavian Journal of Clinical and Laboratory Investigation. - : Informa UK Limited. - 0036-5513 .- 1502-7686. ; 77:5, s. 338-344
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Tidskriftsartikel (refereegranskat)abstract
- Estimating glomerular filtration rate (GFR) in adults by using the average of values obtained by a cystatin C- (eGFRcystatin C) and a creatinine-based (eGFRcreatinine) equation shows at least the same diagnostic performance as GFR estimates obtained by equations using only one of these analytes or by complex equations using both analytes. Comparison of eGFRcystatin C and eGFRcreatinine plays a pivotal role in the diagnosis of Shrunken Pore Syndrome, where low eGFRcystatin C compared to eGFRcreatinine has been associated with higher mortality in adults. The present study was undertaken to elucidate if this concept can also be applied in children. Using iohexol and inulin clearance as gold standard in 702 children, we studied the diagnostic performance of 10 creatinine-based, 5 cystatin C-based and 3 combined cystatin C-creatinine eGFR equations and compared them to the result of the average of 9 pairs of a eGFRcystatin C and a eGFRcreatinine estimate. While creatinine-based GFR estimations are unsuitable in children unless calibrated in a pediatric or mixed pediatric-adult population, cystatin C-based estimations in general performed well in children. The average of a suitable creatinine-based and a cystatin C-based equation generally displayed a better diagnostic performance than estimates obtained by equations using only one of these analytes or by complex equations using both analytes. Comparing eGFRcystatin and eGFRcreatinine may help identify pediatric patients with Shrunken Pore Syndrome.
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| 9. |
- Nyman, Ulf, et al.
(författare)
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Different equations to combine creatinine and cystatin C to predict GFR. Arithmetic mean of existing equations performs as well as complex combinations
- 2009
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Ingår i: Scandinavian Journal of Clinical & Laboratory Investigation. - : Informa UK Limited. - 1502-7686 .- 0036-5513. ; 69:5, s. 619-627
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To test various ways of combining creatinine and cystatin C in equations to predict glomerular filtration rate (GFR). Material and methods: Performance of the following expressions to predict GFR was compared with measured GFR (iohexol clearance, mL/min/1.73 m(2)) in 857 patients: (i) Lund-Malmo creatinine equation, (ii) Grubb cystatin C equation, (iii) arithmetic mean of (1) and (2), (iv) geometric mean of (1) and (2), (v) linear regression on (1) and (2), (vi) regression on (1) and cystatin C, and (vii) regression on creatinine, cystatin C, age and gender. Results: For the entire cohort median percent error (bias) was <5% for all expressions, though all expressions tended to underestimate (<8.3 to <15.8%) GFR at levels <90 mL/min/1.73 m(2). The five expressions combining creatinine and cystatin C significantly improved correlation and accuracy (p < 0.001) within 15 and 30% of measured GFR compared with the equations based on the separate analytes and with no significant difference between the five expressions. In a subgroup of patients with neurological disease and muscle atrophy the cystatin C equation performed better than the expressions combining creatinine and cystatin C. Conclusion: Simply calculating the arithmetic mean of predicted GFR based on separate creatinine and cystatin C equations performs equally well as more complex equations. Reporting GFR based on separate creatinine and cystatin C equations, and their arithmetic mean also has the definite advantage that the physician can choose the estimated GFR, most appropriate depending on the clinical setting and patient characteristics.
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| 10. |
- Nyman, Ulf, et al.
(författare)
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The CKD-EPI and MDRD equations to estimate GFR. Validation in the Swedish Lund-Malmo Study cohort
- 2011
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Ingår i: Scandinavian Journal of Clinical & Laboratory Investigation. - : Informa UK Limited. - 1502-7686 .- 0036-5513. ; 71:2, s. 129-138
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Tidskriftsartikel (refereegranskat)abstract
- Objective. To compare the recently developed CKD-EPI equation to estimate GFR in adult Swedish-Caucasians with the MDRD equation. Material and methods. Swedish-Caucasians (N = 850, 376 females; median age 60, range 5-95 years) referred for plasma iohexol-clearance (median 55, range 5-223 mL/min/1.73 m(2)) constituted the Lund-Malmo Study cohort. Bias, precision (interquartile range, IQR, of the differences between estimated and measured GFR), accuracy expressed as percentage of estimates +/- 10% (P-10) and +/- 30% (P-30) of measured GFR, and classification ability for five GFR stages < 15, 15-29, 30-59, 60-89 and >= 90 mL/min/1.73 m(2) were compared. Results. Overall there were no important differences between the equations; CKD-EPI/MDRD median values of bias +5.4%/+3.4%, IQR both 14 mL/min/1.73 m(2), P-10 36%/34%, P-30 both 80%, and correctly classified GFR stages 68%/67%. P-30 for the CKD-EPI equation was substantially higher than for MDRD at GFR >= 90 mL/min/1.73 m(2) (93% versus 79%). The MDRD equation performed better in the GFR interval 30-89 mL/min/1.73 m(2), while accuracy was limited for both equations at GFR < 30 mL/min/1.73 m(2) (P-30 < 75% in both females and males). The CKD-EPI/MDRD equations caused a +22%/ +14% bias in the 18-39 year interval and the MDRD equation a + 18% bias >= 80 years. Both equations performed poorly in males with BMI < 20 kg/m(2) (CKD-EPI/MDRD median bias +36%/46%). Conclusion. Overall the recently developed CKD-EPI equation performed well but was not superior to the MDRD equation. The CKD-EPI equation may be preferred in screenings of general populations and in the elderly. None of the equations appeared reliable among patients with markedly decreased GFR, young adults and underweight males.
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