Point of Care CRP in the Emergency Department – a scientific clinical case series review

Case series 1. – Acute Exacerbation of COPD

A frequent presentation to the Emergency Department. Acute flair up of airway disease is triggered by viral, bacterial or a mix of both organisms. CRP ( C -Reactive Protein) is a widely used inflammatory biomarker that is used to help the clinician determine the degree of inflammation / infection in various disease processes including sepsis and can help to stratify risk. CRP rises after about 12 – 36 hours of an illness and can reach high levels if the illness goes untreated. CRP rises with viral, bacterial and fungal infections and inflammatory processes like rheumatoid arthritis. A study by T Clark et al Eur Res J (2015) in COPD looked at bacteria and viruses in COPD. They found when CRP < 10 mg/L no virus was identified. A CRP 51-100 mg/L found a virus in 40% of cases and a bacteria in only 5% of cases and mixed virus/ bacteria in 25% of cases. The identity of the organism was interesting – with a CRP 51-100mg/L influenza was found in 8% and streptococcus in 7% and when CRP was > 100mg/L influenza appeared in 7% and streptococcus was also found in 7% of cases.

Antibiotics for COPD and Hospital Admissions

This is a hot topic with antibiotic stewardship and antimicrobial resistance on everyone’s radar. H J Pins at al Eur Res J (2019) used a cut off CRP at 50mg/L when they looked at a group with COPD that were admitted to hospital. They found no serious adverse effects in the cohort group. They reduced antibiotic use in the CRP group by 14.5% compared to a comparative symptom group. C Llor et al Am J Resp Crit Care Med (2012) found similar results with a CRP cut off at 40mg/L. You have the benefit with hospital admission to re-check the CRP in 24 hours after a course of nebulizers and steroids and re-think the antibiotic strategy – not something that’s as easy in the community and primary care. The cut off point for CRP and antibiotic use in COPD may be different in a primary care study group.

Prognosis

No clear evidence from the literature that you can give a prognosis following an admission CRP level in COPD. The prognosis that would be useful would be length of stay and mortality risk. Other biomarkers may have better prognostic features than CRP.

Risk Assessment

When COPD is associated with sepsis and clinical features of severe sepsis e.g the qSOFA score with BP < 100 mm/Hg, Respiratory rate >22 and GCS < 15 a paper by Koozi et al J Crit Care (2019) found a CRP > 100mg/L on ICU admission for sepsis had a greater risk of 30 day mortality and prolonged length of stay in survivors based on the Sepsis 3 criteria.

1. Viral risk is low with a CRP < 20 mg/L if the patient has been unwell for 12-36 hours.

2. Consider antibiotics if CRP > 50mg/L in those patients showing some signs of sepsis. Repeat the CRP after admission for those with CRP > 20 but < 50.

3. Think high risk for those with clear signs of sepsis and CRP > 100mg/L

4. A rapid point of care CRP at the Emergency Department front door can help to risk stratify high from low risk cases of COPD, but has limited ability to differentiate the viral from the bacterial cases when the CRP is raised.