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C-reactive protein in population samples
Insights
C-reactive protein (CRP) is elevated in a small percentage of healthy donors but more common in the general population, often linked to infections or smoking. Elevated CRP was rarely found in pre-illness samples from rheumatoid arthritis patients.
Area of Science:
- Biochemistry
- Immunology
- Clinical Chemistry
Background:
- C-reactive protein (CRP) is a key inflammatory marker.
- Understanding CRP levels in various populations is crucial for diagnostics.
- Previous studies have explored CRP in relation to rheumatoid arthritis and other conditions.
Purpose of the Study:
- To investigate the prevalence and significance of elevated C-reactive protein (CRP) levels in different human specimen sets.
- To assess the association of raised CRP with acute respiratory infections, smoking, and rheumatoid arthritis.
- To evaluate CRP levels in pre-illness sera of individuals who later developed rheumatoid arthritis.
Main Methods:
- Analysis of CRP levels in three distinct specimen groups: healthy blood donors, a general middle-aged population sample, and pre-illness sera from future rheumatoid arthritis patients.
- CRP levels were quantified, with a threshold of >10 mg/l considered raised.
- Correlation of elevated CRP with clinical factors like infections, smoking, and diagnosed rheumatoid arthritis.
Main Results:
- Raised CRP levels (>10 mg/l) were found in 2.0% of healthy donors and 6.6% of a middle-aged population sample.
- Acute respiratory infections (over 40%) and smoking (about 20%) were associated with elevated CRP in the population sample.
- Rheumatoid arthritis was present in 14% of individuals with elevated CRP in the population sample, but only one pre-illness serum specimen showed increased CRP.
Conclusions:
- Elevated CRP is more prevalent in the general population than in healthy donors, often linked to transient conditions like infections or lifestyle factors such as smoking.
- While some individuals with elevated CRP have rheumatoid arthritis, CRP is not consistently elevated in the pre-illness phase of this autoimmune disease.
- CRP's utility as a predictive marker for rheumatoid arthritis development appears limited based on this study.
Abstract:
The significance of C-reactive protein (CRP) was studied in three different sets of specimens. Raised levels (greater than 10 mg/l) were detected in 2.0% of 380 healthy blood donors from whom two blood specimens, taken at an interval of half a year, were tested. Except for two cases, only one of the two specimens was positive. Raised levels were found three times as frequently (in 6.6%) in a random middle-aged population sample consisting of 531 subjects. More than 40% of the raised levels could be connected to acute respiratory infections, and about 20% to smoking. Five of the 35 subjects (14%) in the population sample with elevated CRP had rheumatoid arthritis. The third set of sera comprised pre-illness specimens from 22 subjects who developed rheumatoid arthritis a few months to five years later. Although it had previously been proved that the majority of these sera contained rheumatoid factors, the CRP concentration was increased in one specimen only.