This analysis was undertaken to determine the long-term intraindividual variability, determinants of change, and capacity of the inflammatory marker C-reactive protein (CRP) to predict metabolic traits and diabetes in a large community-based population.

Intraindividual CRP variability, predictors of CRP change, and metabolic events were evaluated in the Framingham Heart Study Offspring cohort using data from the same 2409 participants with CRP measured by the same methodology at each of 3 examination cycles, spanning 20 years.

Between the first and second examinations (averaging 16 years apart), 23% to 47% of men and 27% to 49% of women remained within the same quintile of CRP values. An additional 24% to 51% of men and 24% to 50% of women occupied an adjacent quintile. Intermediate-term CRP variability (over 4 years) was similar to long-term variability. Both long- and intermediate-term variability of CRP were significantly less than that of plasma cholesterol measured in these same groups. Linear regression models for CRP at the intermediate examination demonstrated that CRP at the initial examination contributed the largest proportion of the variability (partial R-square = 0.27) seen in the overall model after adjustment for other covariates known to affect CRP concentrations. Although logistic regression models demonstrated that CRP over the intermediate term did not predict new-onset metabolic syndrome at the final examination, CRP did predict an increase in glucose and new-onset diabetes.

The results of this longitudinal analysis suggest the intraindividual, long-term variability of CRP concentrations is relatively small and predictive of new diabetes over an intermediate-term of 4 years.