CollatedSource of the in vitro diagnostic value circle:Laboratory Medicine Network
Infectious diseases are common types of diseases in clinical practice. They have a wide variety of pathogens, diverse infection routes, and individual differences in symptoms and signs. If they cannot be diagnosed and treated effectively in a timely manner, they can lead to serious consequences. Therefore, how to conduct early diagnosis and/or differential diagnosis of infectious diseases is an urgent practical problem to be solved in clinical practice.
Among the major epidemic infectious diseases, diseases caused by viral infections account for more than half. At present, the novel coronavirus has not yet ended. If it is mistakenly believed to be viralIf an infection is regarded as a bacterial infection, it will delay treatment and aggravate the condition. Therefore, when an infectious disease occurs, it should be identified firstThe type of infection of the patient is particularly important!
Viral infections often act as lymphocytesSerological reference indicatorsThe reference range for the white blood cell count (including neutrophils, lymphocytes, etc.) in the blood routine of the general population is relatively large. Generally, it is believed that only test results exceeding the upper limit of the detection line by 30% have clinical diagnostic significance. Therefore,Relying solely on changes in blood routine as the basis for diagnosing viral infections has certain limitations. The determination of viral infections and their severity also requires the combination of other inflammatory indicators, clinical manifestations, etc. for speculation and judgment. This article sorts out the application of different inflammatory indicators in bacterial and viral infections, especially in COVID-19 infection.
CRPCRP is an acute-phase reaction protein synthesized and secreted by human liver cells. It is one of the most widely used infection diagnostic indicators in clinical practice. When the body is affected by various infections or non-infectious factors such as tissue cell damage, it can cause an increase in CRP, and the increase is relatively rapid. It may appear 5 to 8 hours after the inflammatory response occurs.In evaluating the inflammatory response caused by infection, CRP can not only serve as an indicator for predicting and prognostic sepsis, but is also often used to help distinguish between bacterial and viral infections (see Tables 1 and 2). It usually increases after bacterial infection, while the value is relatively low in most patients with viral infection, < 2-4 mg/L. However, in some cases of viral infection (especially in patients with viral meningitis), its level may increase significantly. The "Diagnosis and Treatment Protocol for Pneumonia Caused by the Novel Coronavirus (Trial Version 7)" also points out that the CRP in the peripheral blood of most patients is elevated, and its progressive increase is a clinical early warning indicator for severe and critical patients.
PCTIt is a powerful piece of evidence for the clinical diagnosis of bacterial infections and has high sensitivity and specificity. When there is a severe systemic bacterial infection, serum PCT can rise early and return to the normal range faster than CRP after the infection is controlled. However, it generally does not increase in local infections. Therefore, it is often used for the diagnosis and differential diagnosis of sepsis, as well as for assessing the severity and progression of sepsis.The PCT level of patients with bacterial pneumonia is higher than that of pneumonia caused by viruses, atypical pathogens (except Legionella), and tuberculosis bacteria. However, not all patients with bacterial pneumonia have elevated PCT levels. 50% of patients with bacterial pneumonia have a PCT of less than 0.5ng/mL, and 28% have a PCT of less than 0.1ng/mL. Therefore, Normal or slightly elevated PCT does not rule out bacterial pneumonia. The level of PCT is positively correlated with the severity of pneumonia. When there is a viral disease, PCT does not increase or only slightly increases, generally not exceeding 1-2 ng/mL. Its sensitivity and specificity in differentiating viral diseases are both higher than those of traditional markers (such as WBC, CRP, ESR, etc.)(See Tables 1 and 2).IL-6It is an important member of the cytokine network and is produced by fibroblasts, monocytes/macrophages, T lymphocytes, B lymphocytes, epithelial cells, keratinocytes, and various tumor cells. It plays a central role in acute inflammatory responses, mediating the acute phase response of the liver and stimulating the production of CRP and fibrinogen. IL-6 is involved in the occurrence and development of many diseases. Inflammation, viral infections, autoimmune diseases, etc. can all lead to an increase in its serum level. Moreover, its changes occur earlier than those of CRP. During bacterial infections, IL-6 rises rapidly, PCT increases after 2 hours, while CRP does not increase rapidly until 6 hours later. Therefore, it can be used to assist in the early diagnosis of acute infections.The level of IL-6 is closely related to the severity of infection and prognosis of patients. When IL-6 is greater than 1000μg/L, it indicates a poor prognosis. The "Diagnosis and Treatment Protocol for Pneumonia Caused by the Novel Coronavirus (Trial Version 7)" points out that the progressive increase of the peripheral blood inflammatory factor IL-6 is a clinical early warning indicator for severe and critical cases. Therefore, dynamic observation of IL-6 levels is helpful for understanding the progression of infectious diseases and the response to treatment (see Tables 1 and 2).SAAIt is a highly heterogeneous protein produced by liver cells. Its core clinical value lies in the differentiation of viral infections and can be used as a sensitive indicator for diagnosing viral and bacterial infections. In bacterial infectious diseases, the sensitivity of SAA is higher than that of CRP, rising earlier and with a larger amplitude. Especially in the early stage of acute bacterial infection, the advantages of detecting SAA are more significant. In viral infectious diseases, SAA is significantly elevated. Depending on the degree of its increase or when used in combination with other indicators, it can indicate bacterial or viral infections, making up for the deficiency that commonly used inflammatory markers currently cannot indicate viral infections.Studies have shown that SAA has good clinical reference value for monitoring the course of viral infection and observing the efficacy of medication. SAA, as a new generation of inflammatory infection indicator, combined with CRP and blood routine diagnosis, is the preferred serological indicator for judging viral infection, monitoring the course of the disease and the efficacy of medication (see Tables 1, 2 and 3). It should be noted that SAA is a non-specific inflammatory marker, and corresponding clinical diagnosis still needs to be made in combination with other clinical evidence.
ESRIt can serve as an auxiliary reference indicator for the diagnosis of many infectious and non-infectious diseases.When acute bacterial inflammation occurs, the erythrocyte sedimentation rate (ESR) will increase within 2 to 3 hours. However, it lacks specificity and there are many influencing factors. The "Diagnosis and Treatment Protocol for Pneumonia Caused by the Novel Coronavirus (Trial Version 7)" indicates that the ESR of most patients is elevated.
The World Health Organization previously reported that 80% of COVID-19 patients have mild symptoms, but the mortality rate of critically ill patients exceeds 50%. Experts say this might be due to the "inflammatory storm" initiated in the bodies of severe patients. The "Diagnosis and Treatment Protocol for Pneumonia Caused by the Novel Coronavirus (Trial Version 7)" points out that most patients have elevated CRP and ESR, while PCT is normal. The progressive increase of peripheral blood inflammatory factors such as IL-6 and CRP is a clinical early warning indicator for severe and critical cases (see Table 4). It is evident that understanding the changes in inflammatory factors in patients after infection is conducive to further strengthening the early diagnosis and treatment of viral infections and taking effective medical treatment measures.This article summarizes and analyzes the commonly used inflammatory indicators in clinical practice at present, aiming to provide scientific support for the clinical diagnosis of infectious pathogens, evaluation of the severity of infections, and monitoring of the infection process in severe patients, so as to select more targeted medication treatment plans. However, it should be noted that at any time, to make a correct clinical diagnosis, one cannot rely solely on the changes of a single biomarker to determine the disease. A comprehensive analysis must be conducted in combination with the patient's clinical manifestations, imaging examinations, other laboratory tests, and epidemiological history, etc.
Heparin-binding protein (HBPIt is an infection indicator that has been widely discussed by experts and scholars in recent years. Both the "2014 Sepsis Treatment Guidelines" and the "Expert Consensus on Early Prevention and Diagnosis of Sepsis 2020" have affirmed the clinical significance of this indicator in the diagnosis, treatment and prediction of sepsis.
The expert consensus points outAs an acute phase protein, HBP is an effective biomarker for evaluating the severity of the disease in patients with sepsis and is even more important in the early diagnosis and therapeutic effect monitoring of patients with septic shock.For patients with severe sepsis, HBP can predict sepsis 10.5 hours in advance, which wins precious rescue time for the patients. It can be said that it is a new star in the field of infection.It is understood that currently, more than 14 provinces in China have obtained the HBP charging code, with prices ranging from 240 to 340. The main focus is on the prediction of sepsis, bacterial meningitis, and the application of HBP in pyelonephritis.
