Use of error grid analysis to evaluate acceptability of a point of care prothrombin time meter

John R. Petersen, Hans M. Vonmarensdorf, Heidi L. Weiss, M. Tarek Elghetany

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Background: Statistical methods (linear regression, correlation analysis, etc.) are frequently employed in comparing methods in the central laboratory (CL). Assessing acceptability of point of care testing (POCT) equipment, however, is more difficult because statistically significant biases may not have an impact on clinical care. We showed how error grid (EG) analysis can be used to evaluate POCT PT INR with the CL. Materials and methods: We compared results from 103 patients seen in an anti-coagulation clinic that were on Coumadin maintenance therapy using fingerstick samples for POCT (Roche CoaguChek XS and S) and citrated venous blood samples for CL (Stago STAR). To compare clinical acceptability of results we developed an EG with zones A, B, C and D. Results: Using 2nd order polynomial equation analysis, POCT results highly correlate with the CL for CoaguChek XS (R2 = 0. 955) and CoaguChek S (R2 = 0. 93), respectively but does not indicate if POCT results are clinically interchangeable with the CL. Using EG it is readily apparent which levels can be considered clinically identical to the CL despite analytical bias. Conclusion: We have demonstrated the usefulness of EG in determining acceptability of POCT PT INR testing and how it can be used to determine cut-offs where differences in POCT results may impact clinical care.

Original languageEnglish (US)
Pages (from-to)131-134
Number of pages4
JournalClinica Chimica Acta
Issue number3-4
StatePublished - Feb 2 2010


  • Coagulation monitoring
  • Error grid analysis
  • POCT
  • PT INR
  • Point of care testing

ASJC Scopus subject areas

  • Biochemistry
  • Clinical Biochemistry
  • Biochemistry, medical


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