|Year : 2020 | Volume
| Issue : 2 | Page : 137-139
Jaffe's kinetic method comparison between isotope dilution mass spectrometry standardized versus nonstandardized method
Girish Konasagara Shanthaveeranna, Anitha Devanath
Department of Biochemistry, St. John's Medical College, Bengaluru, Karnataka, India
|Date of Submission||08-Feb-2020|
|Date of Acceptance||14-Mar-2020|
|Date of Web Publication||23-Jun-2020|
Dr. Girish Konasagara Shanthaveeranna
St. John's Medical College, Bengaluru, Karnataka
Source of Support: None, Conflict of Interest: None
INTRODUCTION: Serum creatinine is estimated by several methods in different laboratories, having varying degrees of bias and imprecision, leading to different values across the laboratories with the same sample. To reduce the interlaboratory variations in creatinine assay, creatinine standardization program was established by the National Kidney Disease Education Program Laboratory Working Group and recommended that creatinine calibration should be done with material traceable to an Isotope dilution mass spectrometry (IDMS) reference measurement procedure.
AIMS AND OBJECTIVE: To compare the serum creatinine estimated by CRE (calibration nonstandardized IDMS with correction factor) and CRE2 (standardized to IDMS) method.
MATERIALS AND METHODS: The study was conducted in a tertiary care hospital as a part of validation of CRE2 method. Two hundred samples were selected from individuals aged between 18 and 60 years with normal serum urea, creatinine, and electrolytes based on the CRE2 method. Further, the sample is estimated for serum creatinine by CRE method on the same instrument with a correction factor (Siemens Dimension RXL with LM). Descriptive statistics and Bland–Altman analysis were used to describe the population and check for agreement between the methods.
RESULTS AND CONCLUSION: The average serum creatinine by CRE and CRE2 method was 0.803 mg/dl and 0.809 mg/dl, respectively. Bland–Altman plot shows a good agreement between the methods for serum creatinine with a mean bias of − 0.01 mg/dL for serum creatinine values ranging from 0.4 to 1.4 mg/dL.
Keywords: CRE, CRE2, Creatinine, IDMS-traceable Jaffe's method
|How to cite this article:|
Shanthaveeranna GK, Devanath A. Jaffe's kinetic method comparison between isotope dilution mass spectrometry standardized versus nonstandardized method. Indian J Health Sci Biomed Res 2020;13:137-9
|How to cite this URL:|
Shanthaveeranna GK, Devanath A. Jaffe's kinetic method comparison between isotope dilution mass spectrometry standardized versus nonstandardized method. Indian J Health Sci Biomed Res [serial online] 2020 [cited 2020 Aug 11];13:137-9. Available from: http://www.ijournalhs.org/text.asp?2020/13/2/137/287420
| Introduction|| |
Creatine is synthesized in the liver from glycine, arginine, and methionine. Creatine in the form of creatine phosphate acts as a ready source of energy in the muscle for muscular contraction. Creatinine is formed in muscle from creatine phosphate or creatine by irreversible, nonenzymatic dehydration, and loss of phosphate. Creatinine is mainly excreted only through urine. In the event of renal dysfunction, the excretion of creatinine decreases, leading to increase in serum creatinine. Hence, serum creatinine estimation is used to monitor renal function.
Different methods for assaying plasma/serum creatinine have varying degrees of bias and imprecision. Reference interval for creatinine clearance and clearance calculated from one of the several formulas will clearly vary depending on the accuracy of the creatinine measurement used in their calculations.
Enzymatic methods give more accurate values and help in better clinical diagnosis and they have shown substantial improvement in calibration, traceability, and precision, as per the National Kidney Disease Education Program (NKDEP) recommendations. Nonenzymatic Jaffe's automated kinetic assay, most commonly used on automated instruments to estimate creatinine, wherein creatinine–picrate reaction rate is measured from 20s to 60s after the start of the reaction, gives 15%–20% of higher values due to interference with noncreatinine chromogens. Therefore, many commercially available Jaffe methods continue to demonstrate an approximately 15%–20% positive bias compared with high-performance liquid chromatography or isotope dilution mass spectroscopy definitive (IDMS) method particularly at concentration within the reference intervals. This calibration between the laboratories is not standardized, leading to variation between laboratories.
To reduce interlaboratory variations in creatinine assay, standardization of creatinine across laboratories becomes crucial to accurately diagnose, stage, and manage chronic kidney disease. Creatinine standardization program was initiated by NKDEP Laboratory Working Group in collaboration with the International Federation of Clinical Chemistry and Laboratory Medicine and the European Federation of Clinical Chemistry and Laboratory Medicine. This helps estimate glomerular filtration rate (eGFR) accurately. In accordance with the above program, the standardization of creatinine calibration should be traceable to an IDMS reference measurement procedure.
In 2011, Siemens Healthcare Diagnostics issued a technical bulletin that provided a correction factor to enable reporting of IDMS-traceable results for the Jaffe methods used with dimension and vista analyzers. NKDEP recommends that users of these methods use the correction factor to conform to the recommendation that all creatinine procedures have calibration traceable to an IDMS reference measurement procedure.
At present, CRE2 method is used for the estimation of creatinine by Siemens Diagnostics that has been calibrated by the calibrator traceable to IDMS method. Earlier CRE method was used and it included the correction factor to account for the differences.
This study was conducted with an intent to evaluate the difference in serum creatinine values between IDMS-traceable method (CRE2 method) versus older version (CRE method) with added correction factor.
| Materials and Methods|| |
This cross-sectional study was conducted in a tertiary care hospital. Samples were initially analysed for serum creatinine by Jaffe's Method standardised to IDMS (CRE2 Method). In these a cohort of 200 apparently healthy subjects belonging to age group 18 to 60 years of either gender with no renal dysfunction evidenced by serum urea, creatinine and electrolytes falling within biological reference interval were selected for the study. These samples were analysed by Jaffe's method non standardised to IDMS method with correction factor (CRE method). The sample analysis was carried out after evaluating for compliance of internal quality controls and on the same day within 20 +/- 10 minutes to ensure that sample integrity is maintained and also to minimise variations. The abnormal results with flags were excluded from the study.
| Results and Discussion|| |
All the samples were analyzed for serum creatinine by CRE and CRE2 method. To check the performance of the creatinine estimation, the quality control performance of the CRE and CRE2 method during the same period was assessed. Coefficients of variation of CRE and CRE2 method were 2.95% and 2.35%, respectively, which were within the acceptable limits (imprecision 2.98%) as per Ricós et al.
The average serum creatinine by CRE and CRE2 method was 0.803 mg/dl and 0.809 mg/dl, respectively. The Bland–Altman analysis was done to check the agreement between the two methods. On analysis, it showed that two methods have a good agreement with a mean bias of -0.01 (confidence interval [CI]: -0.01–0.0). Lower limit of agreement is −0.12 (CI: -0.13–-0.10) and upper limit of agreement is 0.11 (CI: 0.9–0.12) for the serum creatinine ranging from 0.4 to 1.4 mg/dL [Figure 1].
|Figure 1: Bland–Altman plot between CRE and CRE2 method. CRE: Jaffe method with correction factor traceable to IDMS method, CRE2: Jaffe method with calibration traceable to IDMS reference method|
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This explains that the patient results released by CRE method with correction factor was satisfactory and was comparable to IDMS standardized method. A study by Piéroni et al. showed that after standardization to IDMS, there was an improvement in creatinine measurement, with decreased creatinine variability. Lee et al. explained that IDMS standardization has improved creatinine assay accuracy with reduced total error. Srivastava et al. explained the need for establishing newer formula for calculating eGFR with IDMS reference creatinine measurements, because all formulas were based on previous methods.
| Conclusion|| |
CRE method with a correction factor and CRE2 method has good agreement. The results released by CRE method could be compared with the other IDMS-traceable methods during follow-up of the patient and this did not affect the treatment decisions and calculation of GFR. The interlaboratory variability of creatinine can be minimized by complete implementation of the IDMS reference procedure across laboratories.
We thank the Department of Biochemistry for providing us the data for the study.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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