Mouse Anti-Human PCT (aa 96-116) monoclonal antibody, clone B1675M

Procalcitonin (PCT) is a vital biomarker that is increasingly used and researched in infectious diseases, particularly bacteria. PCT is a 116-amino acid precursor protein, that normally exists only in the thyroid C cells, with very low levels in the bloodstream. But with bacterial infection, inflammation or other endocrine stimuli, the PCT spikes rapidly in a variety of tissues and is extremely specific for bacterial infections. Thus, PCT was adopted as a diagnostic of infectious disease and as a test for the efficacy of antibiotics. The precursor protein for PCT consists of CGRP and CT, and PCT is a nonfunctional precursor protein. PCT synthesis is primarily influenced by bacterial infections. When bacteria invade or inflammation is present, PCT is secreted and released by many organs and cells, including the liver, the lungs and the spleen. Under certain inflammatory circumstances, the PCT gene becomes active, leading to rapid spikes in serum PCT. Such an increase rarely occurs in viral infections, so PCT is useful for telling bacterial from viral infections.

Figure 1. Schematic Diagram of PCT Molecule and Its Constituent Peptides. (Source: Samsudin I, Vasikaran SD, 2017)

PCT is so specific for bacteria, so infectious diseases are routinely diagnosed with PCT. Unlike other more familiar inflammatory markers such as C-reactive protein (CRP), PCT is highly sensitive and specific for bacteria, particularly bacterial pneumonia and even lethal sepsis. Researchers have found high PCT levels in patients with bacterial sepsis, but not in patients with viral sepsis. Particularly in intensive care units (ICUs), PCT measurement is integrated into infection risk assessment systems to evaluate infection severity and monitor treatment efficacy. In bacterial pneumonia, for instance, PCT levels can be detected early, correlating positively with infection severity. In patients with acute bacterial infections, PCT tends to go above 2 ng/mL, and in patients with severe bacterial sepsis, they can go above 10 ng/mL, significantly more than in uninfected individuals. PCT is also useful in supporting the prescription of antibiotics. Following the horrifying ramifications of antibiotic resistance to misuse, rational antibiotic use is the world's most urgent problem. Researchers have demonstrated that PCT-assisted therapy reduces unnecessary antibiotic use and enhances patient outcomes. The PCT below 0.5 ng/mL, for example, generally means no treatment is required, whereas the PCT above 2 ng/mL indicates a bacterial infection in need of antibiotics. An ICU-based multicenter clinical trial showed that adjusting the dosage and timing of antibiotics to PCT saved a lot of time on antibiotics without raising infection recurrence or mortality. Antibiotics directed by PCT have also helped to control respiratory infections by reducing the amount of antibiotics needed and eliminating resistance.

In addition to bacterial infections, PCT research has expanded into other conditions. PCT also rises in cardiovascular diseases, like myocardial infarction and chronic heart failure, implying that it is involved in some of these inflammatory and cardiovascular disorders. But in these cases the PCT values are usually modest and it's not easy to separate infectious and non-infectious causes, so it doesn't much good. Additionally, in malignancies, PCT may be slightly elevated but not as significantly as in infectious diseases, where PCTs are used primarily as diagnostic parameters when infection is combined with cancer. Immunocompromised cancer patients are particularly prone to infection, and PCT can distinguish between infection-associated and tumor-associated inflammation. Even though PCT is widely deployed in infectious disease diagnosis, and especially in the ICU and emergency rooms for patients in a critical condition, there are limitations. Variability in PCT levels due to different pathological conditions and individual differences can affect its accuracy. Additionally, certain chronic infections, viral infections, and non-infectious diseases may lead to ambiguity in PCT assessment. The high cost of PCT testing also limits its accessibility in primary healthcare. Therefore, future work must explore how PCT can be combined with other biomarkers to further enhance the diagnostic accuracy and expand its clinical scope. Ultimately, PCT can be a valuable biomarker in diagnosing infectious diseases, monitoring antibiotic use, and treating the seriously ill. Antibiotic interventions directed by PCTs have been successful in facilitating rational antibiotic use and decreasing resistance. As research progresses, the combined application of PCT with other biomarkers will further enhance its role in clinical diagnostics and treatment decisions, offering more reliable support for precision medicine in infectious diseases.

Figure 2. Illustration of the Sandwich Assay Technique as an Example of Immunoassays. (Source: Irwin AD, Carrol ED, 2011)

Procalcitonin Monoclonal Antibody
Anti-Procalcitonin (PCT) Clone