Procalcitonin vs C-reactive protein as predictive markers of response to antibiotic therapy in acute exacerbations of COPD.
BACKGROUND
Rational prescription of antibiotics in acute exacerbations of COPD (AECOPD) requires predictive markers. We aimed to analyze whether markers of systemic inflammation can predict response to antibiotics in AECOPD.


METHODS
We used data from 243 exacerbations out of 205 patients from a placebo-controlled trial on doxycycline in addition to systemic corticosteroids for AECOPD. Clinical and microbiologic response, serum C-reactive protein (CRP) level (cutoffs 5 and 50 mg/L), and serum procalcitonin level (PCT) (cutoffs 0.1 and 0.25 μg) were assessed.


RESULTS
Potential bacterial pathogens were identified in the majority of exacerbations (58%). We found a modest positive correlation between PCT and CRP (r = 0.46, P < .001). The majority of patients (75%) had low PCT levels, with mostly elevated CRP levels. Although CRP levels were higher in the presence of bacteria (median, 33.0 mg/L [interquartile range, 9.75-88.25] vs 17 mg/L [interquartile range, 5.0-61.0] [P = .004]), PCT levels were similar. PCT and CRP performed similarly as markers of clinical success, and we found a clinical success rate of 90% in patients with CRP ≤ 5 mg/L. A significant effect of doxycycline was observed in patients with a PCT level < .1 μg/L (treatment effect, 18.4%; P = .003). A gradually increasing treatment effect of antibiotics (6%, 10%, and 18%), although not significant, was found for patients with CRP values of ≤ 5, 6-50, and > 50 mg/L, respectively.


CONCLUSIONS
Contrary to the current literature, this study suggests that patients with low PCT values do benefit from antibiotics. CRP might be a more valuable marker in these patients.
Daniels
Johannes M A
JM
Department of Pulmonary Diseases, Medical Centre Alkmaar, The Netherlands. j.daniels@vumc.nl
Schoorl
Marianne
M
Snijders
Dominic
D
Knol
Dirk L
DL
Lutter
René
R
Jansen
Henk M
HM
Boersma
Wim G
WG
D000368:Aged; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000378:metabolism*; D002116:Calcitonin / Q000097:blood*; D015740:Calcitonin Gene-Related Peptide; D004318:Doxycycline / Q000627:therapeutic use*; D005260:Female; D005500:Follow-Up Studies; D006023:Glycoproteins; D006801:Humans; D008297:Male; D009391:Nephelometry and Turbidimetry; D011498:Protein Precursors / Q000097:blood*; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood* / Q000188:drug therapy / Q000503:physiopathology; D012008:Recurrence; D012189:Retrospective Studies; D016896:Treatment Outcome
D000900:Anti-Bacterial Agents; D015415:Biomarkers; C000606589:CALCA protein, human; D006023:Glycoproteins; D011498:Protein Precursors; D002116:Calcitonin; D002097:C-Reactive Protein; D015740:Calcitonin Gene-Related Peptide; D004318:Doxycycline