Development of ELISA on microplate for serum C-reactive protein and establishment of age-dependent normal reference range.
BACKGROUND
C-reactive protein (CRP), a marker of systemic inflammation, has been proposed to predict outcome in patients with unstable angina; and elevated levels of CRP were found to be associated with an increased risk of coronary events.


METHODS
Two enzyme-linked immunosorbent assays (ELISA) of different sensitivities were developed on microplate for CRP. Both ELISA established used Dako polyclonal anti-CRP antibody for coating and Dako horse radish peroxidase (HRP)-conjugated polyclonal anti-CRP antibody for detection.


RESULTS
The sensitivity of the high and regular sensitivity ELISA was 0.16 and 0.6 mg/l, respectively. Our assays demonstrated an excellent correlation with commercial CRP assays performed on a Behring Nephelometer Analyzer II (BNII) at both regular and ultrasensitive levels, with both correlation coefficients above 0.98 and slopes of approximately 1. Using our microplate assays, we established normal reference value for serum CRP. Based on ANOVA statistical test, we found that the mean +/- S.D. was 1.3 +/- 1.27 mg/l (n=202) for normal individuals of 50-80 years and 0.43 +/- 0.42 mg/l (n=148) for the group of 20-50 years.


CONCLUSIONS
The normal serum CRP mean concentrations for two age groups were distinctively different (p value<0.001). Our study suggests two different normal cutoffs of serum CRP to be employed for individuals in different age groups.
Wu
Tsu-Lan
TL
Department of Pathology, Chang Gung Memorial Hospital, Taipei, Taiwan.
Tsao
Kuo-Chien
KC
Chang
Christine P -Y
CP
Li
Chia-Ni
CN
Sun
Chien-Feng
CF
Wu
James T
JT
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D002097:C-Reactive Protein / Q000032:analysis* / Q000276:immunology; D002138:Calibration; D004797:Enzyme-Linked Immunosorbent Assay / Q000295:instrumentation* / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013997:Time Factors
D002097:C-Reactive Protein