Comparison of serum procalcitonin in respiratory infections and bloodstream infections.

Purpose: This study observed the relationship between procalcitonin (PCT) and results of sputum culture, the relationship between PCT and results of blood culture to evaluate and compare the value of PCT in respiratory and bloodstream infections.

Methods: We analyzed 1616 patients in which PCT and sputum culture were concurrently ordered and analyzed, and 1096 patients in which PCT and blood culture were concurrently ordered and analyzed from January 2014 to May 2015. PCT concentrations were measured by on a Roche Cobas E601 ECL analyzer.

Results: The average values of PCT from patients with sputum culture positive and negative were 0.42 (0.17-2.16) and 0.12 (0.06-0.57) ng/ml respectively, and the average values of PCT from patients with blood culture positive and negative were 9.54 (2.10-48.47) and 0.28 (0.10-1.23) ng/ml respectively. In sputum culture, positive rate of PCT in cases with growth of pathogens was 47.1%. In blood culture, positive rate of PCT in cases with growth of pathogens was 89.2%.

Conclusions: PCT is useful in early diagnosis of respiratory infections and bloodstream infections, but the specificity of PCT in diagnosing respiratory infections is not as high as it is in bloodstream infections.