Clinical efficacy of an automated high-sensitivity C-reactive protein assay.
BACKGROUND
Prospective studies have shown that C-reactive protein (CRP) can be used to predict risk of future cardiovascular events. High-sensitivity methods for CRP (hs-CRP) measurement are needed for this purpose.


METHODS
We compared the clinical efficacy of an automated and commercially available latex-enhanced assay (Latex) for hs-CRP (Dade Behring) to a validated in-house ELISA, previously shown to predict future peripheral arterial disease (PAD) in asymptomatic populations. Using a prospective, nested, case-control design, we measured baseline hs-CRP concentrations in 144 apparently healthy men who subsequently developed symptomatic PAD and 144 age- and smoking habit-matched controls who remained free of vascular disease over the follow-up period of 60 months.


RESULTS
The two hs-CRP assays correlated highly (r = 0.95; P <0.001), and all but two participants were classified into concordant quartiles or varied by only one quartile. The median hs-CRP of the case group was significantly higher than that of controls when measured by either the ELISA (1.34 vs 0.99 mg/L; P = 0.034) or the Latex method (1.80 vs 1.20 mg/L; P = 0.042). Furthermore, for both ELISA and the Latex method, the calculated relative risks of developing PAD increased significantly with each increasing quartile of hs-CRP. The calculated interquartile increase in relative risk of PAD was 31% (95% confidence interval, 5.2-62.2%; P = 0.01) for ELISA and 34% (95% confidence interval, 8.2-66.1%; P = 0.007) for the Latex method.


CONCLUSIONS
Our findings indicate that the Latex method is equally as efficacious as the validated ELISA in classifying patients into cutoff points established by prospective studies for risk stratification for coronary and cerebrovascular disease.
Rifai
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Department of Laboratory Medicine, Children's Hospital, Harvard Medical School, Boston, MA 02115, USA. rifai@a1.tch.harvard.edu
Tracy
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Ridker
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PM
D000368:Aged; D000369:Aged, 80 and over; D000975:Antioxidants / Q000627:therapeutic use; D001241:Aspirin / Q000627:therapeutic use; D002097:C-Reactive Protein / Q000032:analysis*; D016022:Case-Control Studies; D004311:Double-Blind Method; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007840:Latex; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000097:blood / Q000517:prevention & control; D016491:Peripheral Vascular Diseases / Q000097:blood / Q000517:prevention & control; D010975:Platelet Aggregation Inhibitors / Q000627:therapeutic use; D011446:Prospective Studies; D012307:Risk Factors; D012680:Sensitivity and Specificity; D020521:Stroke / Q000097:blood / Q000517:prevention & control; D019207:beta Carotene / Q000627:therapeutic use
D000975:Antioxidants; D007840:Latex; D010975:Platelet Aggregation Inhibitors; D019207:beta Carotene; D002097:C-Reactive Protein; D001241:Aspirin