The value of C-reactive protein in screening for future coronary heart disease events

Measurement of C-reactive protein (CRP), an inflammatory marker associated with coronary heart disease (CHD) events, has been proposed as a means of screening for future CHD. In prospective studies about a three-fold increase in risk of CHD observed between the top fifth and bottom fifth of the CRP distribution has been taken to support the use of CRP as a screening test. This however gives an over-optimistic impression of its value, because people in the middle of the distribution, where most CHD events occur, are excluded from the analysis. A different analysis is needed to assess whether screening is worthwhile. Examination of the relative frequency distributions of CRP in individuals from 22 prospective studies of individuals without previous cardiovascular disease who subsequently did and did not have a CHD event shows that the detection rate (or sensitivity) was 18% for a false-positive rate of 10% (CRP cut-off 6.65 mg/L); a poor screening test. Whatever CRP cut-off is used, the overlap in CRP values between affected and unaffected individuals is too great for CRP to usefully discriminate between those who will and will not have a CHD event.