Full English name: procalcitonin English abbreviation: PCT
PCT is a protein, and its level in plasma increases when severe bacterial, fungal and parasitic infections, sepsis and multiple organ failure occur. PCT will not increase in autoimmune, allergic and viral infections. Local limited bacterial infection, mild infection and chronic inflammation will not cause its elevation. Bacterial endotoxin plays an important role in the induction process.
PCT reflects the active degree of systemic inflammatory reaction. The factors affecting the level of PCT include the size and type of infected organs, the type of bacteria, the degree of inflammation and the status of immune response. In addition, PCT can only be measured 1~4 days after major surgery in a few patients. The increase of PCT level occurs in severe shock, systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction syndrome (MODS), even without bacterial infection or bacterial lesions. However, in these cases, the PCT level is usually lower than those with bacterial lesions. The release of cytokines or bacterial translocation from the gut may cause induction.
Application of PCT detection in different clinical departments
1. Hematological oncology department
For patients with immunosuppression and neutropenia caused by chemotherapy or bone marrow transplantation, severe infection is a fatal complication. There are many reasons for fever during chemotherapy. Fever is usually a symptom of bacterial, viral or fungal infection, but sometimes it is a reaction to drugs during treatment. Fever caused by tumor cell lysis is relatively common, and the source of fever in most cases is still unclear. PCT is helpful to make a clear diagnosis of systemic infection caused by bacteria and fungi. Even in chemotherapy patients, PCT can reliably detect and evaluate whether there is septicemia infection.
Patients with neutropenia often lack specific symptoms of inflammation. The expression of PCT in patients with immunosuppression and neutropenia was similar to that observed in patients without immunosuppression. Its diagnostic value has been significantly better than CRP and cytokines.
For a long time, patients with bone marrow transplantation or hematopoietic stem cell transplantation have humoral and cellular immune defects, both in quantity and quality, which will cover up serious systemic infections caused by bacteria, fungi, viruses and protozoa. The increase of PCT concentration has a high diagnostic rate for bacterial systemic infection. If septic shock occurs after allotransplantation, the plasma PCT concentration is extremely high, indicating poor prognosis.
2. Anesthesia Department
Postoperative sepsis infection and multiple organ failure are still the most common causes of death in intensive care units. The plasma PCT concentration in small and medium-sized operations is usually within the normal range. For major operations, such as major abdominal operations or chest operations, the PCT concentration often rises within 1-2 days after operation, usually 0.5-2.0 ng · ml-1, occasionally exceeding 5 ng · ml-1. This situation often reduces to the normal level within a few days at the half-life rate of 24 hours. Therefore, it is easy to differentiate the high concentration or persistent high level of PCT caused by infection after operation.
12-24 hours after combined trauma, PCT was moderately elevated, up to 2.0ng · ml-1. For severe lung or chest trauma, PCT was up to 5 ng · ml-1. If there were no infection complications, PCT was generally reduced to the normal range at half-life rate.
3. Internal Medicine
The problems in medical intensive care often revolve around the diagnosis of infection and the differential diagnosis related to infection. Whether the evaluation of the severity of inflammation and its treatment results is effective is a necessary prerequisite for an effective treatment plan.
PCT selectively reacts to systemic bacterial infection, similar bacterial infection and protozoan infection, but has no or only mild response to aseptic inflammation and viral infection. Therefore, PCT can be easily applied to the differential diagnosis of common diseases and syndromes in internal medicine, such as the differential diagnosis of infectious and non-infectious etiology of adult respiratory distress disease; Differential diagnosis of infectious necrosis and aseptic necrosis of pancreatitis; Identify patients with fever during infection, such as tumor and hematological diseases who have received chemotherapy; In patients receiving immunosuppressive agents, the acute exacerbation of chronic autoimmune diseases and rheumatic diseases with systemic bacterial infection were differentiated and diagnosed; Differential diagnosis of bacterial meningitis and viral meningitis; For patients with neutropenia undergoing chemotherapy, determine whether there are life-threatening bacterial and fungal infections; For organ transplant patients receiving immunosuppressive therapy, determine whether there is serious bacterial and fungal infection, and use it for the differential diagnosis of infection and transplant rejection.
4. Transplantation surgery
Successful organ transplantation is often challenged by complications such as severe infection. 31% of patients have infection within the first year after organ transplantation, and the symptoms of infection can be covered up by acute and chronic rejection. Therefore, early and reliable diagnosis of infection during the rejection period cannot be made. The use of PCT detection in organ transplant patients can introduce early treatment to improve survival rate and shorten hospital stay.
PCT is used for the diagnosis of infection in organ transplant patients. Immunosuppressive therapy has seriously weakened the anti-infection ability of organ transplant patients. PCT can indicate the existence of systemic infection as early as 2 hours after the occurrence of infection. PCT in the early stage of infection is more than 0.1 ng · ml-1, with sensitivity of 77% and specificity of 100%. Monthly monitoring of PCT concentration can make a reliable evaluation of the efficacy of anti-microbial therapy.
PCT is applied to organ rejection. One of the main tasks of post-transplant monitoring is to clearly distinguish infection from organ rejection. Because the release of PCT is not caused by the stimulation of acute or chronic organ rejection, high concentration of PCT can be considered as having infection. If the concentration of PCT exceeds 10 ng · ml-1, 98% may be caused by infection rather than organ rejection.
Many diseases have no specific manifestations in premature infants and newborns. Hematology examination, traditional laboratory indicators and acute phase protein can not make a reliable diagnosis of neonatal septicemia. The result of microbiological examination takes several days, and the negative result cannot exclude the existence of clinical infection and the high mortality associated with it. Compared with other inflammatory diagnostic indicators, PCT is an improved laboratory indicator with high sensitivity and specificity in the diagnosis of neonatal postnatal septicemia. PCT can also be used to evaluate the treatment results.
The age-dependent normal value of PCT in premature infants and newborns: PCT reached its physiological peak of 21 ng · ml-1 at 24-30 hours after birth, but the average value was only 2 ng · ml-1,. From the third day after birth, the normal reference value of PCT is the same as that of adults.
PCT is a highly specific indicator of neonatal septicemia: preterm infants and neonatal septicemia infection. PCT can make a diagnosis earlier and more specific than traditional methods, and its sensitivity and specificity for neonatal diagnosis can reach 100%.
It is often difficult to distinguish different sources of infection in children with high fever by clinical means. This problem will affect the accurate diagnosis of patients who are given immunosuppressive therapy due to blood and tumor diseases. Moreover, many diseases are accompanied by secondary immunopathological changes, such as rheumatic fever, so it is difficult to distinguish them from primary bacterial infection in children.
PCT has high sensitivity and specificity in the differential diagnosis of bacterial and viral infections. Because of the essential difference between the treatment of bacterial infection and viral infection, PCT can provide valuable information for the treatment of patients with non-specific infection symptoms.
Detection of proteins and cells in cerebrospinal fluid is not helpful to distinguish bacterial meningitis and viral meningitis in children, and there are obvious cross-phenomena between many specific detection indicators. High concentration of PCT only occurs in bacterial meningitis; The PCT of viral meningitis remained within the normal range (PCT was not detected in cerebrospinal fluid). Monitoring the concentration of PCT by time every day can make a reliable evaluation of the treatment results.
Sepsis infection and multiple organ failure are fatal complications after operation. Although modern medicine has made great progress, there is still no good plan for this. Early and accurate diagnosis of septicemia infection not caused by original disease or surgical trauma itself is the key to successful treatment.
PCT concentration is not affected by existing diseases such as cancer, allergy or autoimmune diseases. PCT is significantly superior to other inflammatory factors such as CRP and cytokines. It is an objective and easy-to-detect indicator, with its unique diagnostic advantages, and even better than those invasive, high-risk and costly diagnostic methods, such as fine needle aspiration pathology.
Application of PCT after operation: PCT is closely related to the occurrence and process of severe bacterial and septicemia infection, and can accurately reflect whether the source of infection causing the disease (such as peritonitis) has been eradicated. Daily monitoring of PCT concentration can make a reliable evaluation of treatment results. PCT can be used to monitor surgical trauma or complex trauma. PCT is used for patients undergoing cardiac surgery. Cardiopulmonary machines are used for cardiac surgery. Even if patients have diseases such as leukocytosis, neutrophilia, eosinophilia or inadequate CRP elevation, the concentration of PCT usually does not increase or only slightly increases, so PCT is very suitable for the detection of sepsis.
With the continuous deepening of clinical and laboratory research and the accumulation of a large number of clinical data, PCT as a routine laboratory indicator for the auxiliary and differential diagnosis of systemic bacterial infection and sepsis will become a consensus and will be promoted. In addition, the exact source and pathophysiological role of PCT in systemic bacterial infection and sepsis still need further study.
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