Background: Blood stream infection is associated with high mortality and morbidity. Blood cultures are considered the gold standard for diagnosing bacteremia in sepsis patients. However, blood culture results may take at least 12 to 24 hours for a positive result and may even be complicated by contamination. Procalcitonin (PCT) a biomarker for bacterial infection is a test with a quick turn-over time of less than 20 minutes and blood sample as little as 0.5mL. The purpose of this study is to identify whether procalcitonin level can be used to determine the risk of bacteremia in hospitalized patients.
Methods: Retrospective analysis of medical records of adult hospitalized patients with suspected bacterial infection and PCT and blood cultures drawn within 24 hours from January 1, 2017 to April 30, 2017 was done in a tertiary medium-sized hospital. A total of 339 records were included for analysis. Based on our lab results procalcitonin value < 0.5 ng/mL defined as low and 0.5 or above defined as elevated procalcitonin. Sensitivity, specificity, positive predictive value and negative predictive value were calculated to assess the performance of procalcitonin levels and blood stream infection. A generalized estimating equation (GEE) was then used to evaluate the differences in length of stay (LOS) and blood stream infection results between patients with high and low procalcitonin.
Results: The mean age was 66 ±17 years and 50% of patients were male. The performance measures of procalcitonin in determining blood stream infection showed a sensitivity of 64%; specificity of 65%; positive predictive value of 13% and negative predictive value of 96%. The over-all statistical accuracy rate was 65%. Patients who had a high procalcitonin level were younger compared to patients with low procalcitonin level (63±17 vs 69±18 yr, p=0.001). High procalcitonin level is associated with longer LOS (median=6 vs 4, p<0.001) and higher risk of blood stream infection (13% vs 4%, p=0.007). The differences were maintained even after adjusting for age differences in the two groups.
Conclusions: Our result shows that an elevated procalcitonin level may not accurately determine bacteremia. However, low procalcitonin can effectively rule out bacteremia. Further study is required to identify an optimal cut-off value to rule out blood stream infection.