Procalcitonin in febrile neutropenia—timing is important

Abstract

Dear Editor, We read with interest the article by Ahn et al., suggesting that adding procalcitonin (PCT) to the MASCC score will improve risk stratification in patients with febrile neutropenia (FN) [1]. We would like to know when the blood for PCT was drawn, in relation to the onset of fever. This is because our reading of the literature, and our own data (which we share here), suggest that the timing of the PCT test is important. Svaldi et al. studied PCT levels at the ‘first appearance of fever’ [2]. PCT was normal in all bacteraemic leucopaenic patients. Similarly, de Bont et al., who drew blood for PCT at the onset with fever, found that their FN patients who had bacteraemia or clinical sepsis did not have a higher first PCT value than those that did not have either of these [3]. We introduced PCT testing into our FN guideline in mid-2010, by asking for PCT to be tested on days 1, 3, and 5 of FN. We share herein the PCT trends of 17 bacteraemic patients over a 6-month period; all had FN after chemotherapy (with curative intent) for acute myeloid or lymphoblastic leukaemia. All patients were inpatient at the time of fever, and all had blood cultures and blood for PCT drawn within an hour (or two) of a temperature spike of at least 38.3 °C. Blood samples for PCT tests were collected into serum separator vacutainer tubes (Becton Dickinson Vacutainer SST, Becton Dickinson, NJ, USA). The samples were centrifuged, and the serum was analysed within 2 h of sample collection. The PCT test was performed using the Roche cobas e601 analyser (Roche Diagnostics GmbH, Germany) using the Elecsys Brahms PCT assay (Roche Diagnostics GmbH). This assay has a total imprecision of coefficient of variation (CV) 2.6 % at PCT concentration of 0.4 ng/mL and CV 1.6 % at PCT concentration of 54.4 ng/mL. Levels below 0.5 ng/mL were considered normal. The plots of the bacteraemic patients' PCT trends are in Fig. 1. Of note, in 14 of these 17 bacteraemic cases, the first PCT reading was in the normal range. As can be seen, the PCT rose subsequently and then decreased. The second PCT reading rose even in the ten patients whose blood culture isolate was susceptible to the antibiotic administered. The kinetics of PCT in healthy volunteers may explain the PCT trends we observed. Dandona et al. injected endotoxin from Escherichia coli into healthy volunteers [4]. They found that PCT values were B. H. Tan (*) Department of Infectious Diseases, Singapore General Hospital, The Academia, 20 College Road, Singapore 169856, Singapore e-mail: tan.ban.hock@sgh.com.sg