One important critique of hs-CRP is that the within-person variability of hs-CRP is high. Studies have shown that hs-CRP fluctuates significantly in people, which calls into question its utility as a risk marker. The higher the hs-CRP value, the more variability there appears to be within the same person over short periods of time (weeks).
In one study, approximately one-third of persons with elevated hs-CRP levels had to be reclassified as having normal hs-CRP levels after repeat testing. This is very concerning. It seems clear now that use of a single hs-CRP measure for risk stratification may lead to substantial misclassification of patients as being falsely high risk or having a falsely low risk. Instead, multiple measurements should be made over weeks to try and get an average baseline. Such repeat testing is not conducive to good cardiovascular screening so hs-CRP is beginning to lose favor as a risk marker.