C-Reactive Protein and White Blood Cell Count as Triage Test Between Urgent and Nonurgent Conditions in 2961 Patients With Acute Abdominal Pain

Abstract

The purpose of this article is to assess the diagnostic accuracy of C-reactive protein (CRP) and white blood cell (WBC) count to discriminate between urgent and nonurgent conditions in patients with acute abdominal pain at the emergency department, thereby guiding the selection of patients for immediate diagnostic imaging.

Data from 3 large published prospective cohort studies of patients with acute abdominal pain were combined in an individual patient data meta-analysis. CRP levels and WBC counts were compared between patients with urgent and nonurgent final diagnoses. Parameters of diagnostic accuracy were calculated for clinically applicable cutoff values of CRP levels and WBC count, and for combinations.

A total of 2961 patients were included of which 1352 patients (45.6%) had an urgent final diagnosis. The median WBC count and CRP levels were significantly higher in the urgent group than in the nonurgent group (12.8 ×10 ⁹/L; interquartile range [IQR] 9.9–16) versus (9.3 ×10 ⁹/L; IQR 7.2–12.1) and (46 mg/L; IQR 12–100 versus 10 mg/L; IQR 7–26) ( P < 0.001).

The highest positive predictive value (PPV) (85.5%) and lowest false positives (14.5%) were reached when cutoff values of CRP level >50 mg/L and WBC count >15 ×10 ⁹/L were combined; however, 85.3% of urgent cases was missed.

A high CRP level (>50 mg/L) combined with a high WBC count (>15 ×10 ⁹/L) leads to the highest PPV. However, this applies only to a small subgroup of patients (8.7%). Overall, CRP levels and WBC count are insufficient markers to be used as a triage test in the selection for diagnostic imaging, even with a longer duration of complaints (>48 hours).