TY - JOUR
T1 - Errors of Classification With Potassium Blood Testing
T2 - The Variability and Repeatability of Critical Clinical Tests
AU - Friedman, Paul A.
AU - Scott, Christopher G.
AU - Bailey, Kent
AU - Baumann, Nikola A.
AU - Albert, David
AU - Attia, Zachi I.
AU - Ladewig, Dorothy J.
AU - Yasin, Omar
AU - Dillon, John J.
AU - Singh, Bhupinder
N1 - Publisher Copyright:
© 2018 Mayo Foundation for Medical Education and Research
PY - 2018/5
Y1 - 2018/5
N2 - Objective: To understand the performance of a currently used clinical blood test with regard to the frequency and size of variation of the results. Patients and Methods: From November 29, 2012, through November 29, 2013, patients were recruited at 65 sites as part of a previously reported clinical trial (ClinicalTrials.gov Identifier: NCT01737697). Eligible outpatients who had been fasting for at least 8 hours underwent venous phlebotomy at baseline, 30 minutes, and 60 minutes to measure plasma potassium levels in whole blood using a point-of-care device (i-STAT, Abbott Laboratories). We analyzed the results to assess their variability and frequency of pseudohyperkalemia and pseudonormokalemia. Results: A total of 1170 patients were included in this study. Absolute differences between pairs of measurements from different time points ranged from 0 to 2.5 mmol/L, with a mean difference of 0.26 mmol/L. The mean percentage differences were approximately 5% with an SD of 5%. Approximately 12% of differences between repeated fasting potassium blood test results were above 0.5 mmol/L (33% of the normal range), and 20% of patients (234) had at least one difference greater than 0.5 mmol/L. In 44.0% of the patients with a hyperkalemic average value (true hyperkalemia) (302 of 686), at least one blood test result was in the normal range (pseudonormokalemia), and in 30.2% of the patients with a normal average value (146 of 484), at least one blood test result was elevated (pseudohyperkalemia). Conclusion: Expected variability and errors exist with potassium blood tests, even when conditions are optimized. Pseudohyperkalemia and pseudonormokalemia are common, indicating a need for thoughtful clinical interpretation of unexpected test results.
AB - Objective: To understand the performance of a currently used clinical blood test with regard to the frequency and size of variation of the results. Patients and Methods: From November 29, 2012, through November 29, 2013, patients were recruited at 65 sites as part of a previously reported clinical trial (ClinicalTrials.gov Identifier: NCT01737697). Eligible outpatients who had been fasting for at least 8 hours underwent venous phlebotomy at baseline, 30 minutes, and 60 minutes to measure plasma potassium levels in whole blood using a point-of-care device (i-STAT, Abbott Laboratories). We analyzed the results to assess their variability and frequency of pseudohyperkalemia and pseudonormokalemia. Results: A total of 1170 patients were included in this study. Absolute differences between pairs of measurements from different time points ranged from 0 to 2.5 mmol/L, with a mean difference of 0.26 mmol/L. The mean percentage differences were approximately 5% with an SD of 5%. Approximately 12% of differences between repeated fasting potassium blood test results were above 0.5 mmol/L (33% of the normal range), and 20% of patients (234) had at least one difference greater than 0.5 mmol/L. In 44.0% of the patients with a hyperkalemic average value (true hyperkalemia) (302 of 686), at least one blood test result was in the normal range (pseudonormokalemia), and in 30.2% of the patients with a normal average value (146 of 484), at least one blood test result was elevated (pseudohyperkalemia). Conclusion: Expected variability and errors exist with potassium blood tests, even when conditions are optimized. Pseudohyperkalemia and pseudonormokalemia are common, indicating a need for thoughtful clinical interpretation of unexpected test results.
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U2 - 10.1016/j.mayocp.2018.03.013
DO - 10.1016/j.mayocp.2018.03.013
M3 - Article
C2 - 29728199
AN - SCOPUS:85046138574
SN - 0025-6196
VL - 93
SP - 566
EP - 572
JO - Mayo Clinic proceedings
JF - Mayo Clinic proceedings
IS - 5
ER -