What do you know about biomolecular markers of infection or sepsis?

More than 250 biomarkers have been identified and evaluated over the past decades, but none accurately differentiate between sepsis and sepsis-like syndromes. Understanding biomarkers of infection or sepsis, pathogen-specific biomarkers and host response biomarkers!

Pathogen-specific biomarkers

Although these microbial nucleic acid testing techniques are becoming increasingly common, their place in the management of passed infections in general (and for bacterial infections in particular) remains unclear. Pathogen-specific biomarkers,Rapid antigen nasal swab such as direct-associated antigen testing, have to been extensively studied for use in critically ill patients.

Most rapid antigen tests are based on immunochromatographic assays and have potential for bedside testing. Influenza and Severe Acute Respiratory Syndrome coronavirus type 2 respiratory antigen tests, as well as Streptococcus pneumoniae and Legionella urinary antigen tests, are sensitive for detecting community-acquired pneumonia but do not accurately consider a negative test result as a rule-out. The Legionella antigen test detects Legionella pneumophila serotype 1, a major cause of Legionnaires' disease, but can also produce false-negative results. The diagnostic accuracy of pneumococcal antigen testing is also highly dependent on serotype, and the introduction of 13-valent polysaccharide conjugate vaccine has reduced its sensitivity due to antigenic shift. Currently, few rapid diagnostic tests are available for the multiplex detection of multiple pathogens in a single sample, and none of the antigen tests provide information on antibiotic susceptibility.

Clostridium difficile infection (CDI) can be diagnosed by a two-step approach that uses a rapid enzyme immunoassay to determine glutamate dehydrogenase (GDH) and free toxins A and B in stool samples from symptomatic patients.The detection of GDH is highly sensitive. If the result is positive, it should be combined with a more specific test for toxin AB. Patients with positive GDH but negative toxin AB tests need to be carefully evaluated, as this may indicate diarrhea or non-toxin-producing C. difficile carriers with toxin levels below the threshold for CDI detection.

The target polysaccharide for fungal antigen analysis is derived from the fungal cell wall. (1,3)-β-d-glucan (BDG) is a pan-fungal serum biomarker commonly used for the detection of invasive candidiasis.BDG has a high sensitivity but low specificity and is an important tool for the elimination of invasive candidiasis in low-prevalence intensive care units (ICUs).

Galactomannan (GM) can be detected in serum and bronchoalveolar lavage (BAL) samples and is highly specific for the diagnosis of invasive pulmonary aspergillosis (IPA). Notably, the GM test for BAL is more sensitive than the serum test in the diagnosis of IPA in non-neutropenic patients and has an important role in the diagnostic criteria for IPA in critically ill patients. Detection of serum cryptococcal antigen is highly predictive of cryptococcal meningitis in HIV patients with CNS symptoms.

Host response biomarkers

Calcitoninogen (PCT) is a hormoneogen that is a precursor to calcitonin.PCT can be produced by virtually all of these organs and by macrophages.PCT begins to rise progressively 3-4 hours after inflammation through stimulation, and only reaches a peak around 24 hours, with a half-life of 22-35 hours.PCT levels are affected by glomerular filtration rate and renal replacement with conventional therapy.PCT-guided antibiotic production management systems have been shown in studies to reduce the use of antibiotics due to improve our clinical primary outcomes. The purpose of PCT testing in critically ill patients is to discontinue antibiotics rather than us enabling antibiotic drug therapy. In non-critically ill patients with a low likelihood of bacterial-viral infections, low PCT levels do not recommend the technical application as well as antibiotics; in some critically ill patients who require some empirical antibiotics as a treatment need to review PCT after 6-24 to redesign the assessment of antibiotics have therapeutic necessity.

C-reactive protein (CRP) is an acute-phase reactive protein that reflects the severity of an infection.CRP is widely used in the clinical diagnosis of acute infectious diseases and in anti-infective treatment.CRP, as a non-specific diagnostic marker, is elevated in many inflammatory processes, but in bacterial-induced infectious diseases, the level of CRP is significantly higher than that of non-infectious diseases.There are many factors that affect CRP, such as the presence of a bacterial agent, the presence of a bacterial agent, and the presence of a bacterial agent. Many factors affect CRP, and common leukocyte changes may have a significant effect on CRP. Therefore, the clinical application of CRP should consider whether the elevation of CRP is combined with other factors, and the combination of CRP and other markers (e.g., PCT) can greatly enhance the value of CRP.