Research ArticleResearch

Causes and outcomes of markedly elevated C-reactive protein levels

Alexander Landry, Peter Docherty, Sylvie Ouellette and Louis Jacques Cartier
Canadian Family Physician June 2017; 63 (6) e316-e323;

Article Figures & Data

Figures

  • Figure 1.
    Figure 1.

    Primary infection sites associated with markedly elevated CRP levels: N = 462; numbers above the columns represent the peak CRP level in mg/L for that site.

    CRP—C-reactive protein, GI—gastrointestinal.

    *Other infections included endocarditis, pharyngitis, osteomyelitis, and vascular graft infections.

  • Figure 2.
    Figure 2.

    Medians, interquartile ranges, and outliers of peak CRP levels by diagnostic category

    CRP—C-reactive protein.

  • Figure 3.
    Figure 3.

    Medians, interquartile ranges, and outliers of peak CRP levels associated with medications

    CRP—C-reactive protein, DMARD—disease-modifying antirheumatic drug, TNF—tumour necrosis factor.

    *Biologic agents include anti-TNF agents, rituximab (7 cases), and abatacept (1 case).

Tables

  • Table 1.

    Causes of markedly elevated CRP levels: N = 839 patients.

    DIAGNOSISPATIENTS, N (%)
    Infection462 (55.1)
    Inflammatory45 (5.4)
    Rheumatologic63 (7.5)
    Malignancy43 (5.1)
    Drug reaction14 (1.7)
    Multiple*47 (5.6)
    Uncertain148 (17.6)
    Other17 (2.0)

    • CRP—C-reactive protein.

    • ↵* Of the 47 patients who had multiple diagnoses, 46 also had infection.

  • Table 2.

    Noninfectious diagnoses and associated peak CRP values

    DIAGNOSISNO. OF PATIENTSPEAK CRP LEVEL, mg/L
    Rheumatologic63361.0
    Solid tumour25325.0
    Pericarditis20277.0
    Inflammatory bowel disease21203.2
    Hematologic malignancy18321.0
    Drug reaction14321.0
    COPD exacerbation5312.9

    • COPD—chronic obstructive pulmonary disease, CRP—C-reactive protein.

  • Table 3.

    Unusual causes of markedly elevated CRP levels

    DIAGNOSISNO. OF PATIENTSPEAK CRP LEVEL, mg/L
    Venous thrombosis2247.9
    Bowel obstruction2218.0
    Gastrointestinal ischemia2123.0
    Ischemic extremity1118.0
    Rhabdomyolysis1183.0
    Hematoma1136.0

    • CRP—C-reactive protein.

  • Table 4.

    Patients with rheumatologic diagnoses whose CRP levels remained above different cutoffs: Septic arthritis was considered an infection but its results are shown here for comparison.

    DIAGNOSISNO. AT PEAK CRP LEVEL
    > 100 mg/L> 150 mg/L> 200 mg/L> 250 mg/L> 300 mg/L> 350 mg/L> 400 mg/L> 500 mg/L
    Septic arthritis412719116331
    Rheumatologic
      • Crystal-induced arthritis2512553100
      • Vasculitis106221000
      • Rheumatoid arthritis10320000
      • Other inflammatory arthritis104110000
      • Polymyalgia rheumatica62100000
      • SLE*21100000

    • CRP—C-reactive protein, SLE—systemic lupus erythematosus.

    • ↵* The 2 patients with SLE both had isolated pericarditis.

  • Table 5.

    Outcomes of patients based on diagnostic category

    DIAGNOSISHOSPITALIZEDMORTALITY, %
    ADMITTED, %MEAN NO. OF DAYSINTENSIVE CARE, %
    Infection (n = 462)77.910.010.09.0
    Rheumatologic (n = 63)41.27.61.60.0
    Malignancy (n = 43)83.718.57.037.0
    Drug reaction (n = 14)71.48.414.00.0
    Multiple (n = 47)93.615.06.021.0
    Inflammatory (n = 45)88.99.020.04.0
    Other (n = 17)88.213.612.06.0
    Uncertain (n = 148)25.09.02.01.0
  • Table 6.

    Outcomes of patients based on initial WBC count

    SAMPLEHOSPITALIZED, %MORTALITY, %
    Leukopenia (n = 29)86.220.7*
    Normal WBC count (n = 297)61.68.4
    Leukocytosis (n = 510)71.48.0
    Overall (n = 836)67.78.6

    • WBC—white blood cell.

    • ↵* Significant at P = .002 using Fisher exact test.

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Causes and outcomes of markedly elevated C-reactive protein levels
Alexander Landry, Peter Docherty, Sylvie Ouellette, Louis Jacques Cartier
Canadian Family Physician Jun 2017, 63 (6) e316-e323;
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