A prospective study of daily measurement of C-reactive protein in serum of adults with neutropenia.

A total of 1,622 daily measurements of the level of C-reactive protein (CRP) in the serum of 40 hospitalized patients with neutropenia were made during 55 study periods from October 1990 through February 1993 (mean, 29.5 measurements per period). Clinical events were categorized into four groups: group I (bloodstream infection), group II (significant bacterial or fungal infection without bloodstream infection), group III (fever without an obvious source), and group IV (drug-related fever). There was a strong association between baseline elevation of the CRP level (> or = 100 mg/L) and tumor-associated fever (P = .0005); the resolution of such fever coincided with a decrease in the CRP level following chemotherapy. Levels of CRP increased by > or = 40 mg/L in 10 (31%) of 32 cases during the 48-72 hours preceding the clinical diagnosis of a subsequently demonstrable infection--often pneumonia without bloodstream infection. CRP values on day 2 (1 day after the diagnosis of a clinical event) were significantly higher for events in groups I and II than for those in group III (P < .01) but not those in group IV. With regard to significant infections, a day-2 CRP value of > or = 40 mg/L was 100% sensitive and an increase in CRP level of > or = 50 mg/L from day 1 to day 2 had a positive predictive value of 95%. We conclude that serial measurements of serum CRP levels may be helpful in determining the extent of evaluation required for a newly febrile neutropenic patient and possibly in accelerating the detection of an otherwise unsuspected infection.