[Neutrophilic leukocytosis of systemic or bacterial origin: discriminative C-reactive protein?]

Neutrophilic leucocytosis is frequent in systemic diseases and often leads to confusion with infective diseases. A C-reactive protein (CRP) level of 100 mg/l or more has been claimed to indicate a bacterial infection in over 80% of the cases. The purpose of this study was to test the discriminative value of CRP in patients with neutrophilic leucocytosis of bacterial or systemic origin. Sixty patients presenting with an inflammatory syndrome with neutrophilia entered the study and were divided into 2 groups. Group I comprised 30 patients with Horton's disease (n = 9), systemic vasculitis (n = 6), deep cancer (n = 5), connective tissue disease (n = 4) or Still's disease (n = 4). Group II consisted on 30 patients with infective diseases: septicaemia (n = 13), bacterial pneumonia (n = 12), pyelonephritis (n = 4) or cholecystitis (n = 1). In both groups the number of neutrophils was higher than 12,000/cubic mm. Mean CRP values were lower in group I (75.3 +/- 70 mg/l) than in group II (153 +/- 61 mg/l) (P less than 0.01). With values above 100 mg/l the specificity and sensitivity of CRP for infection were 45% and 55% respectively; the positive predictive value of CRP was 66% and its negative predictive value 76%. Specificity rose to 65% with a CRP level higher than 150 mg/l, and 74% for a CRP level higher than 200 mg/l, but such values were also observed in 4 patients of group I.(ABSTRACT TRUNCATED AT 250 WORDS)