Causes and outcomes of markedly elevated C-reactive protein levels.

OBJECTIVE: To characterize the causes of marked elevation of C-reactive protein (CRP) levels, investigate patient outcomes, and examine factors that might influence the CRP response.

DESIGN: Health records were used to retrospectively determine patient characteristics, diagnoses, and outcomes over a 2-year period (2012 to 2013).

SETTING: A large referral centre in Moncton, NB.

PARTICIPANTS: Adult inpatients and outpatients with a CRP level above 100 mg/L.

MAIN OUTCOME MEASURES: Differences among the CRP distributions of various diagnosis categories were examined using Kruskal-Wallis tests, and factors affecting outcomes were examined using Fisher exact tests.

RESULTS: Over the 2-year period, 1260 CRP levels (839 patients; 3.1% of all tests) were above 100 mg/L (range 100.1 to 576.0 mg/L). The mean age was 63 years (range 18 to 101) and 50.2% of patients were men. Infection was the most prevalent cause (55.1%), followed by rheumatologic diseases (7.5%), multiple causes (5.6%), other inflammatory conditions (5.4%), malignancy (5.1%), drug reactions (1.7%), and other conditions (2.0%). A diagnosis could not be established in 17.6% of cases. On average, infections caused higher peak CRP levels ( W = 34 519, P < .001) and infection was present in 88.9% of cases with CRP levels greater than 350 mg/L. Rheumatologic causes were associated with only 5.6% of CRP levels above 250 mg/L. The overall mortality was 8.6% and was higher in patients with malignancy (37.0%), multiple diagnoses (21.0%), and leukopenia (20.7%, P = .002).

CONCLUSION: Most patients had infections and the proportion of patients with infections increased with the level of CRP, although many diagnoses were associated with markedly elevated CRP levels. These data could help guide health care professionals in the evaluation and management of these patients.