Published online by Cambridge University Press: 09 March 2011
Owing to systemic inflammatory response syndrome, the diagnosis of post-operative infection after cardiopulmonary bypass is difficult to assess in children with the usual clinical and biological tools. Procalcitonin could be informative in this context.
Retrospective study in a paediatric intensive care unit. Blood samples were collected as soon as infection was clinically suspected and a second assay was performed 24 hours later. Using referenced criteria, children were retrospectively classified into two groups: infected and non-infected.
Out of the 95 children included, 14 were infected. Before the third post-operative day, procalcitonin median concentration was significantly higher in the infected group than in the non-infected group – 20.24 nanograms per millilitre with a 25th and 75th interquartile of 15.52–35.71 versus 0.72 nanograms per millilitre with a 25th and 75th interquartile of 0.28 to 5.44 (p = 0.008). The area under the receiver operating characteristic curve was 0.89 with 95% confidence intervals from 0.80 to 0.97. The best cut-off value to differentiate infected children from healthy children was 13 nanograms per millilitre with 100% sensitivity – 95% confidence intervals from 51 to 100 – and 85% specificity – 95% confidence intervals from 72 to 91. After the third post-operative day, procalcitonin was not significantly higher in infected children – 2 nanograms per millilitre with a 25th and 75th interquartile of 0.18 to 12.42 versus 0.37 nanograms per millilitre with a 25th and 75th interquartile of 0.24 to 1.32 (p = 0.26). The area under the receiver operating characteristic curve was 0.62 with 95% confidence intervals from 0.47 to 0.77. A procalcitonin value of 0.38 nanograms per millilitre provided a sensitivity of 70% with 95% confidence intervals from 39 to 89 for a specificity of 52% with 95% confidence intervals from 34 to 68. After the third post-operative day, a second assay at a 24-hour interval can improve the sensitivity of the test.
Procalcitonin seems to be a discriminating marker of bacterial infection during the post-operative days following cardiopulmonary bypass in children.