Serum procalcitonin (PCT) has been proposed as a marker to identify bacterial infection in children. For optimal management of cystic fibrosis (CF) patients, early recognition of pulmonary exacerbations is necessary, but sensitive biomarkers to do so are lacking. Our study was done to establish baseline values for PCT in children with CF and to compare these to values at onset of a pulmonary exacerbation. Serum PCT values were determined in CF children during an outpatient clinic visit and at onset of treatment with intravenous (IV) antibiotics for a pulmonary exacerbation. Serum PCT was measured using a quantitative immunoassay (BRAHMS Kryptor PCTsensitive, Henningsdorf, Germany). In 92 outpatients (mean age 10.0 years, SD 4.8 years; mean forced expiratory volume in 1 s 91%, SD 18; 9 chronically colonized with Pseudomonas aeruginosa), mean baseline PCT was 0.05 ng/ml (SD 0.07). Mean PCT on admission for IV treatment of pulmonary exacerbation was 0.07 ng/ml (SD 0.06) (n = 22) and not different from the baseline value. PCT values were markedly higher in two CF patients with an acute nonrespiratory infection (central venous catheter-associated bloodstream infection, acute gastroenteritis), demonstrating that they can mount a PCT response.
Conclusion: PCT values in CF children are not different from values reported in healthy children. In CF children, PCT values do not rise significantly at the onset of a respiratory exacerbation and thus hold no promise as an early marker to identify a pulmonary exacerbation.