Locally smoothed median absolute difference curves and the first global performance cooperative: Relevance to glycemic variability and underserved populations

Gerald J Kost, Nam Tran, Jorge R. Sifontes, Dan M. Mecozzi, Richard F. Louie, Victor J. Abad

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


We present US multicenter results, multinational performance, and a global performance cooperative. We use locally smoothed median absolute difference (LS MAD) curves to reveal bedside glucose testing performance through rapid visual discrimination and hypothesize that (a) inaccuracy and open-loop feedback systems cause glycemic variability adversely affecting outcomes in tight glycemic control (TGC) and (b) poor performance increases a risk for underserved populations where hospital and primary care staff may use glucose meter systems (GMSs) in critical therapeutic decisions.The US methods are the following: modified glucose oxidase enzyme with a multilayer-gold, multielectrode, 4-well test strip (StatStrip, NOVA Biomedical, Waltham, Mass); pragmatic comparison of GMS results versus paired plasma glucose level measurements from chemistry analyzers in clinical laboratories; venous samples (2767) at 59 US hospitals with 21 chemistry analyzer types; erroneous results identified using a Bland-Altman plot and the International Organization for Standardization 15197 criteria; and analysis of values discrepant for TGC. The global method is synopsis of LS MAD curves.The US GMS met the International Organization for Standardization 15197 tolerances: 98.86% (607/614) of observations were within tolerance for a glucose level lower than 75 mg/dL and 99.81% (2149/2153) for 75 mg/dL or higher. The mean (SD) paired difference was -2.92 (9.6) mg/dL (median, -2; range, -96 to +45). Locally smoothed MAD curve analysis revealed a satisfactory performance below 179 mg/dL; above 179 mg/dL, the recommended error tolerance limit (5 mg/dL) was not met. No discrepant values appeared. All paired observations fell within Clarke error grid zone A. Linear regression showed y = 1.019 × -0.233 mg/dL; r = 0.995. In contrast, LS MAD curves for other types of GMSs used outside the United States showed inconsistencies.The US LS MAD curve results presented here benchmark a high standard. We invite readers to submit data sets for analysis and to participate in a new point-of-care performance cooperative. This global forum can advance bedside glucose testing expectations by motivating the more accurate and precise devices better standardized and harmonized for use with patients who have diabetes, TGC, and low-resource settings.

Original languageEnglish (US)
Pages (from-to)45-52
Number of pages8
JournalPoint of Care
Issue number2
StatePublished - Jun 2009


  • Bandwidth
  • Discrepant values
  • Erroneous results
  • Hypotheses
  • ISO 15197 guideline
  • Locally smoothed median absolute difference curve
  • Outcomes

ASJC Scopus subject areas

  • Nursing(all)


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