Detection of Acute Phase Response and Infection. The Role of Procalcitonin and C-Reactive Protein
Authors: Rothenburger Markus , Markewitz Andreas , Lenz Thomas , Kaulbach Hans-Georg , Marohl Klaus , Kuhlmann Wolf-Dieter , Weinhold Christian 
Published: October 2004

Objective: Established parameters, e.g. C-reactive protein
(CRP), do not differentiate specifically enough
between patients developing an infection and those
exhibiting an acute phase response following cardiac
surgery. The objective of this prospecitive study was
to investigate if procalcitonin (PCT) ist more helpful
than CRP.

Methods: During a 1-year period, seven out of 563
patients (1.2 %) developed systemic infections (group
A) after cardiac operations with cardiopulmonary bypass
(CPB), and additional eight patients (1.4 %) had
local wound infections requiring surgical therapy
(group B). Blood samples for PCT and CRP measurements
were taken preoperatively, at the onset of infection
(d1), as well as on the third day (d3), fifth day (d5),
and seventh day (d7) following diagnosis of infection.
Forty-four randomly selected patients undergoing cardiac
surgery with CPB without clinical signs of infection,
additional intensive care unit (ICU) management
or additional antibiotic treatment served as control
(group C) to assess the PCT and CRP contribution to
acute phase response. PCT and CRP levels were measured
preoperatively, on the first (d1), third (d3) and
fifth day (d5) after operation.

Results: At the onset of infection, PCT levels (median
interquartile range 25 %–75 %) increased significantly
in group A as compared to baseline values
(10.86 (3.28–15.13) ng/ml vs. 0.12 (0.08–0.21) ng/ml),
and decreased during treatment to still significantly
elevated values on d5 (0.56 (0.51–0.85) ng/ml). CRP
levels were significantly elevated on all days investigated
with no trend towards normalisation (d1: 164.5
(137–223) mg/l) vs. 1.95 (1.1–2.8) mg/l preoperatively,
d5: 181.1 (134–189.6) mg/l. In group B, no increase in
PCT levels, but a significant increase of CRP from d1
(165.9 (96.6–181.6) mg/l) vs. 3.7 (2–4.3) mg/l preopratively)
until d5 98 (92.8–226.2) mg/l was detected. In
group C, postoperative PCT levels increased slightly
but significantly in the absence of infection on d1
(0.46 (0.26–0.77) ng/ml vs. 0.13 (0.08–0.19) ng/ml preoperatively),
and d3 (0.37 (0.2–0.65) ng/ml and
reached baseline on d5 (0.24 (0.11–0.51) ng/ml)). CRP
levels were significantly elevated as compared to
baseline on all postoperative days investigated (baseline:
1.75 (0.6–2.9) mg/l, d1: 97.5 (74.5–120) mg/l), d3:
114 (83.05–168.5) mg/l, d5: 51.4 (27.4–99.8) mg/l)). PCT
showed a significant correlation to CRP in group A (r = 0.48, p < 0.001), a weak correlation in group C (r = 0.27, p = 0.002) and no correlation in group B. Intergroup
comparison revealed a significant difference for
PCT between all groups (A > C >B) and significantly
higher CRP levels in group A vs. C and in group B vs.
C. Thus, the pattern high PCT/high CRP appears to indicate
a systemic infection, while low PCT/high CRP
indicates either acute phase response or local wound
problems, but no systemic infection. The cost for PCT
measurements was 5.6-fold higher as compared to
CRP.

Conclusion: Due to the significant differences in the
degree of increase, PCT appears to be useful in discriminating
between acute phase response following
cardiac surgery with CPB or local problems and
systemic infections, with additional CRP-measurement
increasing the specifity.