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Colegio de Medicina Interna de México.

2006, Number 3

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Med Int Mex 2006; 22 (3)

Intra-class coefficient correlation vs Pearson correlation of capillary glycemia by reflectometry and plasmatic glycemia

Esquivel MCG, Velasco RVM, Martínez RCE, Barbachano RE, González ÁG, Castillo RCE

Language: Spanish
References: 28
Page: 165-171
PDF size: 252.03 Kb.


ABSTRACT

Background: Bedside blood glucose quantitative measurements with reflectometry in uncontrolled diabetic patients give a high correlation with rp from 0.97 to 0.98, which is thought to have a great clinical utility. This has been the concept during the last years; however the simple correlation of Pearson (rp), with bivariated distribution is used to evaluate agreement among continuous numeric variables, but this does not measure the possible systematic bias, the advisable one is the variance analysis when the variables are numeric with the intra-class coefficient correlation (CCI). Objectives: To assess and to contrast rp and CCI in two samples the glucose measurements by reflectometry and plasmatic glucose. Patients and methods: In a prospective, blinded, crossover contrasted study two samples were included with 18 and 151 subjects each. It was measured the capillary glycemia, by reflectometry and by venopuncture with self-analyzer with the glucose oxidase-peroxidase method. Descriptive analysis was used, as well as test of Kolmogorov-Smirnov (K-S) for distribution determination. The analysis was done with rp, IC 95% zr and CCI with variance analysis ANOVA IC 95%. Statistical package: SPSS V 8.0. Microsoft Excel 2000. Results: We obtained the following results in the pilot sample rp = 0.9063 IC 95% zr (0.839-0.942) and CCI = 0.8853 IC 95% (0.7203-0.9555), F =16.447 p = 0.0000. Correlation for the sample of 151 with rp = 0.9797 IC 95% zr (0.954-0.984). Intra-class coefficient correlation (CCI) = 0.9776 IC 95% (0.9693-0.9837). Conclusions: This study shows the advantage of using and detecting the systematic bias with CCI instead of rp for agreement between reflectometry and plasmatic glycemia quantified as continuous numeric variables.


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