Utility of Procalcitonin in the Early Diagnosis of Patients with Sickle Cell Disease Presenting with Fever

Background: Patients with sickle cell disease (SCD) are at increased risk of developing bacterial infections as a result of functional asplenia. Fever, a common symptom in SCD often occurs with other sickle cell related conditions and viral infections. This poses a diagnostic challenge and early use of empiric antibiotics is recommended while awaiting cultures. The widespread administration of antibiotics to all patients with SCD with fever can result in problems such as antibiotic resistance and increased medical costs. An early and reliable biomarker is therefore needed to help distinguish between bacterial and non-bacterial causes for fever in SCD. Procalcitonin (PCT) has been shown to be elevated in bacterial but not viral infections. In SCD, few studies have looked at the role of PCT in predicting bacterial infections. Unal et al reported vaso-occlusive crisis (VOC) with or without fever did not increase PCT levels in relation to patients with no crisis and no fever. However, Rincón‐López et al reported a PCT < 0.6ng/mL had a negative predictive value of 97.2% and potentially could be used to identify bacterial infection early.

Methods: We retrospectively studied 122 patients with SCD who presented to the emergency department with fever from 2015-2019. Inclusion criteria were defined as patients with SCD, 17 years and older and PCT measurement on presentation to the emergency department. Exclusion criteria were defined as patients with SCD and fever who had received empiric antibiotics prior to labs being drawn in the emergency department. The cohort was divided into groups of patients with Confirmed Bacterial Infection (CBI, n=18), Suspected Bacterial Infection (SBI, n=6), Viral Infections (n=10) and Vaso-Occlusive Crises (VOC, n=88) only. CBI was defined as a positive bacterial culture (blood, body fluid, urine, respiratory or cerebrospinal fluid) or C.difficile toxin assay. Viral infections were defined as a negative bacterial culture in the presence of a virus found on PCR obtained with nasopharyngeal swab. Characteristics including genotype, age, gender, complete blood count, PCT, creatinine, total bilirubin, hydroxyurea use and length of stay were examined. Data was analyzed between the groups using descriptive statistics and accounting for unequal variances, with p-value set at 0.05 for significance.

Results: Demographics and clinical characteristics are summarized in Table 1 (Figure). The mean age was 34.6 years with predominantly males (64.8%). Almost two-thirds were on hydroxyurea (62.3%). The most common genotype was HbSS (70.5%) followed by HbSC (26.2%) and HbSβ (3.3%). The mean PCT for patients with CBI was 8.99 ng/mL (range, 0.03-78.36) as compared to 0.31 ng/mL (range, 0.02-6.82) in the VOC group. The most common organisms detected were E.coli, C.difficile, Pseudomonas, Staphylococcus and Enterobacter. There was a significant difference between median PCT for patients with CBI and those with VOC (p=0.036) and between patients with CBI and viral infections (p= 0.045). Using a PCT of >0.5ng/mL resulted in 81% Sensitivity and 85% Specificity for CBI.

Conclusion: In patients with SCD presenting with fever, PCT on presentation was significantly higher in those with CBI compared to VOC only or Viral Infection.