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Effect of glucose interference with Jaffe creatinine measurement on EGFR calculation
Abstracts
Results: The ratio of HVA/VMA in the patient'’s urine was 23.6, which was approximately 6-fold higher than the population reference range (b4.0). The patient was subsequently found to have a c.2383C N T mutation in the ATP7A (p.R795X), thus confirming the diagnosis of MD. Conclusions: An elevated urinary HVA/VMA ratio in premature infants with a complicated clinical picture is strongly indicative of MD. It is important for clinical laboratory scientists to be aware of this biochemical phenomenon when investigating and screening suspected patients, as low serum copper levels are non-diagnostic. doi:10.1016/j.clinbiochem.2015.07.073
331 Effect of glucose interference with Jaffe creatinine measurement on EGFR calculation Stephen Hilla, Andrew Don-Wauchopeb, Peter Kavsakc, Edward Campbelld, Bonnie Malloryd a McMaster University, Hamilton, ON, Canada b Hamilton Regional Laboratory Medicine Program, Hamilton, ON, Canada c Juravinski Hospital & Cancer Centre, Core Lab, Hamilton, ON, Canada d McMaster Children's Hospital, Hamilton, ON, Canada Background: Glucose interference with the Jaffe creatinine method is well described. We investigated the effect of glucose interference on Jaffe creatinine measurement, using the Abbott 4100, on calculated eGFR. Method: Glucose interference was estimated by adding various amounts of glucose to a pooled patient sample. All samples from patients N18 years, with both glucose and Jaffe creatinine were recovered. Creatinine was “corrected” using an estimate of 1.0 mmol/L glucose = 1.0 umol/L false increase in creatinine. MDRD eGFR was calculated using both creatinine values. Results: 278 paired data were recovered. In all cases the eGFR estimate for the uncorrected creatinine was lesser than the eGFR for the corrected creatinine. In 8 (2.8%) cases the eGFR moved from b60 to N60 mls/min/1.73 m2.
1019
332 Comparison of multiplexed assessment of celiac autoantibodies to an ELISA-based method reveals good performance of a multiplexing platform Lori Beach, Waliul Khan McMaster University, Hamilton, ON, Canada Background: Celiac disease is an autoimmune disorder globally affecting between 1-in-100 to 1-in-170 individuals of every age. Molecular screening for the disorder has been aided by the use of assays specific for tissue transglutaminase (TTG) and deaminated gliadin peptide (DGP) Igs. While TTG IgA is found in individuals with active disease, this diagnosis is challenged in IgA-deficient patients. One solution is second-tier IgG testing, however multiplexed methods for simultaneous determination of TTG IgG, TTG IgA, DGP IgG and DGP IgA are also available. The objective of this study was to compare the performance of a multiplex-based method to an ELISAbased method. Methods/results: Serum samples tested for TTG IgA were screened for positive results as determined by an ELISA kit from INOVA (cut-off ≥ 4 U/mL; n = 98). Age and gender were determined for all positive samples and negative control samples were matched from TTG-negative serum samples without IgA deficiency. All samples were then assayed for TTG IgA (INOVA) and DGP IgG (INOVA) by ELISA and compared to Biorad's TTG IgA and IgG as well as DGP IgA and IgG kits by Bioplex. Direct comparison of TTG IgA results revealed that the Bioplex method exhibited a result concordance of 95.9% (sensitivity) and 97.6% (specificity). The Bioplex analysis of DGP IgG exhibited result concordance of 93.5% and 84.0%. Conclusion: The multiplexed Biorad method of simultaneous IgG and IgA determination of TTG and DGP exhibits good comparability with ELISA-based assays and may provide a more rapid assessment of Celiac status in patients developing IgA deficiency. doi:10.1016/j.clinbiochem.2015.07.075
333 Verification of the Randox beta-hydroxybutyrate assay on the Abbott Architect platform for rapid assessment of ketosis Lori Beach, Lynn Ford, Stephen Hill McMaster University, Hamilton, ON, Canada
Conclusion: Positive glucose interference with creatinine measurement results in underestimation of the eGFR, especially at low creatinine concentrations. This may result in errors in eGFR interpretation. doi:10.1016/j.clinbiochem.2015.07.074
Objectives: Ketone bodies, generated in response to fatty acid mobilization that exceeds the capacity of the Krebs' cycle, consist of acetone, acetoacetate and beta-hydroxybutyrate (BHB). Their detection is valuable in cases of diabetic ketoacidosis as well as in investigation of pediatric hypoglycemia. BHB is the predominant (N75%), as well as the most rapidly changing ketone in ketosis. To improve testing turn-around time of BHB at McMaster Children's Hospital, we verified the performance of the quantitative Randox D3-hydroxybutyrate assay on the Architect platform. Design and methods/results: Using quality control (QC) material diluted into blank patient serum, acceptable precision was verified (1.9% CV and 0.6% CV at 0.29 mmol/L and 1.17 mmol/L, respectively). Limit of detection was determined to be 0.111 mmol/L. Patient comparisons to another BHB method were carried out. Both serum and vitreous fluid sample types showed a positive bias with the Randox method (11.8% for serum and 6.8% for vitreous fluid). Interference studies revealed the importance of testing for interferences at more than one analyte concentration: a significant positive bias is observed in hemolyzed samples (N1 g/L hemoglobin) at low BHB concentrations, leading to falsely elevated BHB results. In contrast, the effect of hemolysis is less pronounced at higher BHB
Results: The ratio of HVA/VMA in the patient'’s urine was 23.6, which was approximately 6-fold higher than the population reference range (b4.0). The patient was subsequently found to have a c.2383C N T mutation in the ATP7A (p.R795X), thus confirming the diagnosis of MD. Conclusions: An elevated urinary HVA/VMA ratio in premature infants with a complicated clinical picture is strongly indicative of MD. It is important for clinical laboratory scientists to be aware of this biochemical phenomenon when investigating and screening suspected patients, as low serum copper levels are non-diagnostic. doi:10.1016/j.clinbiochem.2015.07.073
331 Effect of glucose interference with Jaffe creatinine measurement on EGFR calculation Stephen Hilla, Andrew Don-Wauchopeb, Peter Kavsakc, Edward Campbelld, Bonnie Malloryd a McMaster University, Hamilton, ON, Canada b Hamilton Regional Laboratory Medicine Program, Hamilton, ON, Canada c Juravinski Hospital & Cancer Centre, Core Lab, Hamilton, ON, Canada d McMaster Children's Hospital, Hamilton, ON, Canada Background: Glucose interference with the Jaffe creatinine method is well described. We investigated the effect of glucose interference on Jaffe creatinine measurement, using the Abbott 4100, on calculated eGFR. Method: Glucose interference was estimated by adding various amounts of glucose to a pooled patient sample. All samples from patients N18 years, with both glucose and Jaffe creatinine were recovered. Creatinine was “corrected” using an estimate of 1.0 mmol/L glucose = 1.0 umol/L false increase in creatinine. MDRD eGFR was calculated using both creatinine values. Results: 278 paired data were recovered. In all cases the eGFR estimate for the uncorrected creatinine was lesser than the eGFR for the corrected creatinine. In 8 (2.8%) cases the eGFR moved from b60 to N60 mls/min/1.73 m2.
1019
332 Comparison of multiplexed assessment of celiac autoantibodies to an ELISA-based method reveals good performance of a multiplexing platform Lori Beach, Waliul Khan McMaster University, Hamilton, ON, Canada Background: Celiac disease is an autoimmune disorder globally affecting between 1-in-100 to 1-in-170 individuals of every age. Molecular screening for the disorder has been aided by the use of assays specific for tissue transglutaminase (TTG) and deaminated gliadin peptide (DGP) Igs. While TTG IgA is found in individuals with active disease, this diagnosis is challenged in IgA-deficient patients. One solution is second-tier IgG testing, however multiplexed methods for simultaneous determination of TTG IgG, TTG IgA, DGP IgG and DGP IgA are also available. The objective of this study was to compare the performance of a multiplex-based method to an ELISAbased method. Methods/results: Serum samples tested for TTG IgA were screened for positive results as determined by an ELISA kit from INOVA (cut-off ≥ 4 U/mL; n = 98). Age and gender were determined for all positive samples and negative control samples were matched from TTG-negative serum samples without IgA deficiency. All samples were then assayed for TTG IgA (INOVA) and DGP IgG (INOVA) by ELISA and compared to Biorad's TTG IgA and IgG as well as DGP IgA and IgG kits by Bioplex. Direct comparison of TTG IgA results revealed that the Bioplex method exhibited a result concordance of 95.9% (sensitivity) and 97.6% (specificity). The Bioplex analysis of DGP IgG exhibited result concordance of 93.5% and 84.0%. Conclusion: The multiplexed Biorad method of simultaneous IgG and IgA determination of TTG and DGP exhibits good comparability with ELISA-based assays and may provide a more rapid assessment of Celiac status in patients developing IgA deficiency. doi:10.1016/j.clinbiochem.2015.07.075
333 Verification of the Randox beta-hydroxybutyrate assay on the Abbott Architect platform for rapid assessment of ketosis Lori Beach, Lynn Ford, Stephen Hill McMaster University, Hamilton, ON, Canada
Conclusion: Positive glucose interference with creatinine measurement results in underestimation of the eGFR, especially at low creatinine concentrations. This may result in errors in eGFR interpretation. doi:10.1016/j.clinbiochem.2015.07.074
Objectives: Ketone bodies, generated in response to fatty acid mobilization that exceeds the capacity of the Krebs' cycle, consist of acetone, acetoacetate and beta-hydroxybutyrate (BHB). Their detection is valuable in cases of diabetic ketoacidosis as well as in investigation of pediatric hypoglycemia. BHB is the predominant (N75%), as well as the most rapidly changing ketone in ketosis. To improve testing turn-around time of BHB at McMaster Children's Hospital, we verified the performance of the quantitative Randox D3-hydroxybutyrate assay on the Architect platform. Design and methods/results: Using quality control (QC) material diluted into blank patient serum, acceptable precision was verified (1.9% CV and 0.6% CV at 0.29 mmol/L and 1.17 mmol/L, respectively). Limit of detection was determined to be 0.111 mmol/L. Patient comparisons to another BHB method were carried out. Both serum and vitreous fluid sample types showed a positive bias with the Randox method (11.8% for serum and 6.8% for vitreous fluid). Interference studies revealed the importance of testing for interferences at more than one analyte concentration: a significant positive bias is observed in hemolyzed samples (N1 g/L hemoglobin) at low BHB concentrations, leading to falsely elevated BHB results. In contrast, the effect of hemolysis is less pronounced at higher BHB