Some research studies clearly establish that the elevation of hs-CRP is associated with increased cardiovascular risk, while others fail to find this relationship. Where is the problem of this disagreement?: in the populations studied,in the design of the studies, or in the method of measurement?
Methods of measuring hscrp are not equivalent. It is based on percentile to cut down the lab errors. I believe the problem is with the cut off values which makes it difficult to come to any relevant judgment. ?..
Some years ago, the FDA established clear differences between hs-CRP and the so called cCRP. This difference, guided by the fact that the cCRP may be useful as an independent marker of prognosis for recurrent events, in patients with stable coronary disease or acute coronary syndrome, raised a great discusion. (http://www.fda.gov/downloads/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/ucm071017.pdf)
In these times when differences in the utility of c (hs) CRP as markers of cardiovascular risk is observed, we could say that the FDA was right and not all methods are equivalent?
The problem is one of terminology. CRP is a well defined pentraxine with known structure. Terms such as hs-CRP, c-CRP are misleading, as they suggest different molecular forms of CRP which are useful for certain diagnostic procedures. The terms only reflect the capability of different methods to detect CRP. Nephelometric / turbidimetric methods usually detect CRP above ca. 5 mg/l. Immunoassays (RIA, LIA) can measure down to under 0.1 mg/l with sufficient analytical sensitivity (lower limit of quantification - LLOQ). In a general healthy population the median CRP-level is around 0.9-1.0 mg/l, the 97.5th centile around 3.5-4.0 mg. This means that the conventional nephelometric methods were unable to measure "normal" CRP. With latex enhancement, this was improved, but still the majority of healthy individuals remain undetectable.
The question is: "What do I want to investigate and which CRP method is most suitable?". This problem is not limited to CRP, but includes other analytes, especially "sensitive" assays for PSA, free-PSA, complexed-PSA as well as non-existent analytes such as "microalbumin" (what is meant here is micro-albuminuria, something completely different!) and the members of the "hCG-family". Commercial concerns are not entirely free from blame for these disillusions, as they suggest new important diagnostic tests for specific use. Using the appropriate assay with the correct statistics usually leads to useful scientifically based results which answer the question posed.
Hallo,
First of all it depends on the standards used. The WHO (Fa. Behring) has produced 50000 liters of pure standard CRP. If this standard is used, then the first problem is solved. Then, there is the reproducibility of different labs. If you take the Ringversuche of DGKL for glucose, for example, which is so well defined almost as no other molecule!. The target value of one was 100 mg/100 ml. The values offered by well known german laboratiries varied between 80 and 180 mg/dl. Now you have the answer!
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