Procalcitonin (PCT) is a biomarker that, when used in conjunction with other laboratory findings and clinical assessments, can indicate the risk of bacterial infection. In addition, PCT also has a role to play in confronting the coronavirus. It can identify a superimposed bacterial infection and thus support the use of antibiotics only in those COVID-19 patients who need it.
In recent, evolving studies, PCT has identified COVID-19 patients at low risk for bacterial coinfection and adverse outcome.1-7 While the majority of COVID-19 patients can avoid antibiotics altogether, one study of 38 Michigan hospitals found that antibiotics may have been started in COVID-19 patients “just in case.” In these hospitals, 56.6% of patients were prescribed early, empiric antibacterial therapy despite a low prevalence of confirmed bacterial infection (3.5%).8 Inappropriate antibiotic prescribing can be harmful, sometimes deadly, and leads to increased antibiotic exposure and resistance.
PCT on admission
Test PCT as an aid for early risk assessment of patients at high risk of bacterial coinfection.
PCT during hospital stay
Monitor PCT to detect secondary infections and progression of the severity of bacterial infection.
0.25 - < 0.5 μg/L* - low risk for bacterial coinfection and adverse outcome
≥ 0.5 μg/L* - high risk patients, bacterial coinfection likely
*Majority of patients with mild disease had PCT values < 0.25 μg/L or even < 0.1μg/L.1-6 Likelihood of bacterial infection and recommendation to start antibiotics in patients with lower respiratory tract infection at PCT > 0.25 μg/L.15
An analysis of 1,099 COVID-19 patient data sets from medical centers in China show that PCT was low (< 0.5 µg/L) in > 96% of cases with low disease severity and absence of adverse outcome (combined endpoint of ICU admission, invasive ventilation, death).2 In fact, most COVID-19 patients had PCT values < 0.25 µg/L or even < 0.1 µg/L.2-3 This correlates to findings from previous viral epidemics (influenza H1N1, SARS, MERS) that PCT is usually low (< 0.1 - < 0.5 µg/L) in hospitalized patients with pure viral infection.9-14
In cases with bacterial coinfection and higher severity of disease, PCT has been found to be higher (> 0.5 µg/L).1-6 Thus, according to a recent meta-analysis of published COVID-19 patient data, PCT > 0.5 µg/L corresponds to an almost five-times higher risk of severe infection (OR, 4.76; 95% CI, 2.74-8.29) compared to patients with lower PCT.15 Acute Respiratory Distress Syndrome (ARDS) and septic shock were the most frequent complications of COVID-19; secondary infections during the hospital stay were an additional risk factor.1-6 Patient mortality was almost always associated with sepsis/septic shock and respiratory failure/ARDS.2,3,6,9
With the right biomarkers in place, hospitals have the opportunity to bolster their antibiotic stewardship programs and reduce unnecessary antibiotic exposure. Procalcitonin equips clinicians with objective insights, making it easier to determine whether to prescribe or discontinue antibiotic therapy. Such a customized treatment approach is only possible if the proper education is in place.
The IFCC identifies PCT on the Recommended Test List for potential clinical and biological significance in recognizing bacterial (super) infection:17
"The essential role of clinical laboratories in this pandemic extends beyond etiological diagnosis of COVID- 19. Biochemical monitoring of COVID-19 patients through in vitro diagnostic testing is critical for assessing disease severity and progression as well as monitoring therapeutic intervention. Several common in vitro diagnostic tests have been implicated in unfavourable COVID-19 progression, potentially providing important prognostic information."17
Treatment of Community-Acquired Pneumonia During the Coronavirus Disease 2019 (COVID-19) Pandemic:18
"...We endorse the use of a low procalcitonin value early in the course of confirmed COVID-19 illness to guide the withholding or early stopping of antibiotics, especially among patients with less severe disease."18
The CDC identifies PCT among a list of inflammatory markers correlating to the severity of illness.19
"Procalcitonin is typically normal on admission but may increase among those admitted to the ICU. Patients with critical illness had high plasma levels of inflammatory markers, suggesting potential immune dysregulation."19