C-Reactive Protein Values in Pediatric Patients

Normal Values and Interpretation

• Normal CRP in children is <3 mg/L (<28.6 µmol/L), consistent with adult reference ranges 1
• CRP values between 3-10 mg/L (28.6-95.2 µmol/L) suggest low-grade chronic inflammation 1
• CRP >10 mg/L (>95.2 µmol/L) indicates acute inflammation or infection in pediatric patients 2, 3, 4, 5

Diagnostic Cut-offs for Specific Conditions

• For acute appendicitis in children, CRP ≥10 mg/L (≥95.2 µmol/L) is a strong predictor, particularly in children <6 years old 2, 5
• For acute appendicitis in children, CRP >40 mg/L (>380.8 µmol/L) was found in 58% of complicated appendicitis cases 2
• For Multisystem Inflammatory Syndrome in Children (MIS-C), marked elevation is defined as CRP ≥10 mg/dL (≥100 mg/L or ≥952 µmol/L), which is a criterion for hospital admission 3, 4, 6
• For Multisystem Inflammatory Syndrome in Children (MIS-C), most cases display CRP values >10-20 mg/dL (>100-200 mg/L or >952-1904 µmol/L) 3
• For influenza in children, CRP is unhelpful, with 55% of cases having values <10 mg/L (<95.2 µmol/L) and only 5% having values >80 mg/L (>761.6 µmol/L) 7

Clinical Pitfalls

• The traditional 10 mg/L cut-off for "pathological" CRP is outdated and should not be used to automatically exclude participants or dismiss clinical concern, as many non-infectious factors can elevate CRP above this threshold 8, 1