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ORIGINAL ARTICLES |
Nephrology Division,1 Department of Medicine, University of Hong Kong; Department of Chemical Pathology,2 Prince of Wales Hospital, Shatin; Clinical Biochemistry Unit,3 University of Hong Kong, Hong Kong
Correspondence to: K.N. Lai, Department of Medicine, University of Hong Kong, Queen Mary Hospital, no. 102, Pokfulam Road, Hong Kong. knlai{at}hkucc.hku.hk
Background: Peritonitis is the major complication in
patients undergoing maintenance peritoneal dialysis (PD) and is associated
with a significant risk of mortality. Previously, we have shown that patients
treated for peritonitis and having prolonged elevation of C-reactive protein
(CRP) are associated with higher mortality. The underlying cause for the
chronic systemic inflammation remains unknown. We studied serum procalcitonin
(PCT), which has been reported as an accurate marker for infection and
inflammation, with respect to being a diagnostic and prognostic indicator of
persistent chronic inflammation after peritonitis in patients with PD-related
peritonitis. Methods: We conducted a prospective study on PD
patients that developed PD-related peritonitis. Blood samples obtained at
routine check-up before the onset of peritonitis were taken as baseline (D0).
When patients developed PD-related peritonitis, serial blood samples were
obtained on day 1 (D1), day 7 (D7), and day 42 (D42) for PCT, CRP, and other
inflammatory markers. Patients were followed up for at least 2 years, during
which outcomes of peritonitis and causes of death were recorded. Serum levels
of CRP and PCT at day 42 were analyzed to assess for long-term
prognosis. Results: 35 patients [female 42.9%; mean age 63.8
± 13.1 years; 12 (34.3%) diabetics] were recruited. The onset of
peritonitis was 3.61 ± 3.56 years after PD initiation and median
residual renal function at that time was 1.06 (range 0 – 6.1) mL/min.
Median total white cell counts in PD effluent at days 1, 3, 7, and 42 were
3505/mm3 (range 377 – 20 500/mm3), 297 (8 –
5880)/mm3, 34 (0 – 5290)/mm3, and 10 (0 –
115)/mm3, respectively. Twelve (34.3%) and 14 (40%) PD effluents
grew gram-positive and gram-negative micro-organisms respectively; others were
culture negative. Median PCT was increased significantly at day 1 [2.00 (0.12
– 58.7) ng/mL, p < 0.001], day 7 [0.76 (0.13 – 15.25)
ng/mL, p < 0.001], and day 42 [0.30 (0.13 – 0.79) ng/mL,
p = 0.005] compared to baseline [0.20 (0.09 – 0.69) ng/mL].
Seven of 35 patients had false-negative results on day 1 (range 0.12 –
0.46) when PCT <0.5 ng/mL was used as the cutoff value for diagnosing
peritonitis. For the long-term prognostic outcome, CRP at day 42 was
significantly better than PCT in assessing overall prognosis (CRP: AUC 0.712,
95% CI 0.534 – 0.890 vs PCT: AUC 0.652, 95% CI 0.448 – 0.855). In
Kaplan–Meier survival analysis, patients with elevated CRP (>3.0
mg/L) were associated with poorer long-term survival (p = 0.04) but
elevated PCT at the 25th, 50th, or 75th percentiles failed to provide
prognostic value. Conclusions: PD patients after peritonitis may be
associated with prolonged systemic inflammation. CRP was a better serum marker
for monitoring inflammatory status and predicting long-term prognosis in our
study. Although serum PCT is elevated in some patients at the time of
peritonitis, its value in making a diagnosis and predicting long-term
prognosis remains doubtful.
KEY WORDS: Peritonitis; inflammation; procalcitonin; C-reactive protein.
Received 6 August 2007; accepted 29 January 2008.
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