Clinical Use of ESR and CRP

Primary Recommendations

The American Heart Association recommends prioritizing CRP over ESR for diagnosing acute inflammatory conditions due to its superior analyte characteristics, rapid response to inflammation, and better correlation with disease activity, while ESR remains valuable for monitoring chronic inflammatory diseases 1
The American College of Cardiology recommends using CRP for cardiovascular risk assessment, obtaining 2 measurements 2 weeks apart and averaging the results in metabolically stable patients 1

CRP is the preferred inflammatory marker for acute infections and inflammatory conditions, as it rises and falls rapidly with active inflammation, making it superior for diagnosis and monitoring treatment response in acute settings 1
CRP correlates better with endoscopic activity in Crohn's disease than ESR, with a clinically relevant cutoff of 5 mg/L 2
Normal CRP (<5 mg/L) combined with low fecal calprotectin effectively excludes active inflammation with 81% sensitivity 2
Elevated baseline CRP predicts better response to anti-TNF therapy 2

ESR is specifically indicated for giant cell arteritis (GCA) diagnosis, with ESR >40 mm/h having 93.2% sensitivity and a negative likelihood ratio of 0.18 3
ESR is valuable for monitoring polymyalgia rheumatica (PMR), with ESR >40 mm/h predicting higher relapse rates 3
ESR contributes 15% of DAS28-ESR calculations for rheumatoid arthritis disease activity 3
ESR ≥70 mm/h supports the diagnosis of osteomyelitis in diabetic foot infections 3

CRP results should be expressed only as mg/L to 1 decimal point 1
Risk categories for CRP are: low risk <1.0 mg/L, average risk 1.0-3.0 mg/L, high risk >3.0 mg/L 1
If CRP >10 mg/L, the test should be repeated and sources of infection or inflammation examined 1
ESR interpretation thresholds are: elevated >20 mm/h in men, >30 mm/h in women 3
Moderate elevation of ESR (50-100 mm/h) indicates a greater likelihood of significant disease 3

The European Crohn's and Colitis Organisation recommends using ESR >30 mm/h (or CRP >30 mg/L as substitute) to define severity in severe ulcerative colitis, with a validated marker in the Truelove and Witts criteria 4
The American College of Gastroenterology suggests that ESR is incorporated into the assessment of inflammatory bowel disease activity, although CRP correlates better with endoscopic activity in Crohn's disease 5

The European League Against Rheumatism recommends ordering both ESR and CRP for the initial evaluation of undifferentiated inflammatory arthritis for both diagnostic and prognostic purposes 5