OBJECTIVE: To compare procalcitonin measurements between semi-quantitative and quantitative assays. METHOD: Procalcitonin was measured with the PCT-Q and the Kryptor assays in a pediatric emergency department. RESULTS: Among the 359 pairs of results, 103 had discordant results. The linear weighted kappa was 0.44 (95% CI 0.36, 0.51). The concordant/discordant results distribution varied depending on the laboratory technician (p=0.018). CONCLUSION: Agreement between procalcitonin measured semi-quantitatively and quantitatively was moderate. This is probably due to a subjective interpretation of the assay result.