Research status and perspective in laboratory diagnosis of syphilis
[Background]Syphilis is a sexually transmitted disease caused by Treponema pallidum,which can damage the nervous,cardiovascular,digestive and urinary systems,seriously endangering human health.In recent years,the number of syphilis cases has been increasing annually.The number of reported syphilis cases ranks third among legally reported infectious diseases,following viral hepatitis and tuberculosis,and first among sexually transmitted diseases,which has raised wide spread concern and become a global public health issue.At present,the clinical stage composition of new syphilis cases has undergone significant changes.The proportion of primary and secondary syphilis of dominant syphilis and the proportion of fetal syphilis have gradually decreased,while the incidence of recessive syphilis has increased year by year.Given that syphilis is a great imitator and its course is occult,complex and diverse,there is an urgent need for highly sensitive diagnostic methods and effective monitoring indicators to enable early diagnosis and treatment.[Progress]This article reviews the research status of laboratory detection methods and algorithms of syphilis.Pathogen examination can directly confirm infection,but it is susceptible to factors such as sampling site and sampling method,resulting in low sensitivity.Serological tests are the primary method for the diagnosis of syphilis,but because antibodies are produced at least 2 weeks after infection,it is difficult to screen patients during the window period.Due to the lack of a unified industry standard for serological diagnostic algorithms,the selection of the three serological diagnostic algorithms by various laboratories is also different.Polymerase chain reaction(PCR)has high sensitivity and specificity for lesions of patients with primary or secondary syphilis,but for easily obtained blood samples,the positive rate of T.pallidum DNA is low.To date,no syphilis PCR detection reagent has obtained a medical device registration certificate in China,preventing its clinical application.[Perspective]First,the development of a joint detection reagent for T.pallidum antibody and non-specific antibody can avoid missed diagnosis of false negative results due to the initial screening method of the three diagnostic algorithms,promptly identify the disease status of patients,and detect syphilis cases at various stages with maximum sensitivity and specificity.This approach can effectively reduce the workload and contribute to the early diagnosis of syphilis.Secondly,the detection window period of serological tests is long,generally several weeks,which often coincides with an important infectious period,facilitating the spread of disease.As the component of the pathogen itself,the antigens can appear after the pathogen has invaded the body.Research on the antigen spectrum of blood,cerebrospinal fluid,urine and other specimens is expected to shorten the detection window period.Finally,there is no internationally approved assay for syphilis PCR,and laboratories have established methods based on their own needs without rigorous performance verification and systematic evaluation.In the future,the quality control management of clinical molecular detection can serve as a reference,with evaluation and strict performance verification conducted in areas such as detection personnel,instruments and equipment,experimental reagent materials,detection methods,and laboratory environment.This will help develop unified standards for molecular diagnosis of syphilis and ultimately lead to in vitro diagnostic products of syphilis molecular detection with quality control.
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