Question 1: Can TORCH screening diagnose birth defects?
No. TORCH screening is the diagnosis of infection in pregnant women and thus provides concern for the presence of infection and developmental defects in the fetus. Screening screens for individuals (infected) at high risk of a disease (virus) in the population (pregnant women), diagnoses the latter (diagnosis of fetal infection), and intervenes with patients (fetuses) or carriers of the disease (virus) (pregnant women) for prevention and treatment purposes.
Question 2: What are the common features of TORCH infections?
1. Mother-to-child transmission, fetal risk at T1 stage and neonatal risk at T3 stage.
2. Pregnant women are asymptomatic or have very mild symptoms.
3, The virus can cause intrauterine infection through the placenta, which can cause premature birth, miscarriage, stillbirth or malformation, etc.
4, the virus through the birth canal or breast milk infection of newborns cause neonatal multi-system and organ damage, mental retardation.
5, pregnant women are infected, the fetus is not necessarily infected, and fetal infection does not necessarily cause birth defects.
Question 3: What are the differences of TORCH infection?
After infection of the organism, Toxoplasma gondii, rubella virus, cytomegalovirus and herpes simplex virus serological changes vary (Figure 2), as do antibody changes, and the degree of antibody changes need to be quantified to make a correct judgment.
Question 4: What is the difference in clinical significance of the indicators for TORCH infection testing?
1, direct indicators (viral antigen, viral DNA, viral RNA viral culture) detect the virus itself, related to the replication pattern and latent location of the virus and other characteristics, suitable for diagnosis.
2. Indirect indicators (IgG, IgM) detect the immune response generated by the body after the virus stimulates the body, which is related to the immune function of the individual and is suitable for screening and immune status assessment.
Question 5: How many types of infections are there in pregnancy?
Infections during pregnancy are divided into primary infection, previous infection, recurrent infection, and reinfection, and their concepts should not be confused.
1. primaryinfection, also known as primary infection: the first time a pregnant woman’s serum is positive for virus-specific antibodies IgG and the previous serological test is negative is called primary infection. The IgG antibody affinity assay, in the case of a positive IgG test, helps to distinguish between an acute primary infection, a previous infection or a recurrent infection, and to estimate the time of primary infection, i.e., if the test result is high affinity, it is possible to conclude that the primary infection occurred 3 months ago. If the test result is high affinity, it can be concluded that the first infection is 3 months ago.
2, pastinfection: the virus has been infected before, the body has produced antibodies or the virus is dormant in a latent state.
3, recurrentinfections/secondaryinfection: intermittent excretion of the virus in the presence of host immune function, is the latent state of endogenous virus reactivation.
4, reinfections (reinfections): individuals who have been immunized are exposed to an exogenous new virus and reinfection occurs. Currently, it is not possible to distinguish recurrent infections and reinfections by serological methods, but only by viral isolation and molecular biology.
5. Congenital infections (congenitalinfections): the result of trans-placental transmission of the virus. Initial or recurrent infection of the mother can transmit the virus to the fetus, resulting in congenital infection of the fetus.
Question 6: Why should screening tests IgG and IgM be done at the same time?
Screening tests for IgG and IgM should be done at the same time, as IgM alone often gives incorrect results. positive IgM is not sufficient proof of recent infection, and in some populations IgM can be present continuously for several years after infection, so a positive IgM alone is not diagnostic. If we take the IgM of rubella non-acute infection as an example, the reasons for this can be divided into the following two cases.
1, IgM true positive: This is due to the fact that some people have continued to have IgM expression in their bodies for many years after the onset of infection, often with IgM levels remaining low and stable, often accompanied by IgG positive and also maintaining stable levels. In this case, the IgM result obtained by the kit is correct, but it does not mean that the individual is experiencing acute infection, so if only IgM is tested alone, it will cause misjudgment.
False positive IgM: This is mainly due to the influence of rheumatoid factor (RF), cross-reactivity or polyclonal stimulation, which leads to incorrect results of the kit.
Positive IgM results for non-acute infections due to both of these conditions can then cause confusion in clinical diagnosis, as these individuals are not undergoing acute infection. However, this problem can be satisfactorily corrected by simultaneous IgG testing with quantitative detection reagents. In the case of “2”, if the initial test is IgM-positive/IgG-negative, the second test 15 days-1 month later, the individual will remain in this situation or the IgM will be negative, i.e., no serological conversion of IgG will occur; if the initial test is IgM-positive or /IgG-positive, the second test 15 days-1 month later will not tend to show a significant change in the values of these two indicators. The IgG in particular will remain stable because the individual has not had a true recurrence of infection.
Question 7: Why is TORCH screening in pregnancy time-sensitive?
Different viruses have different screening goals and different requirements for the week of gestation at which they are screened; without a week of gestation, screening results are often meaningless. Some viruses are meaningful when screened in early pregnancy and some are meaningful when screened in late pregnancy.
Question 8: Why is there no absolute reference value for antibody screening?
TORCH virus infection is a dynamic maternal-fetal process and there is no definitive standard for each time period. For example, a 4-fold increase in IgG is often used as an indicator of viral recurrence or reinfection.
Q9: Why is quantitative analysis an advancement and the best choice for TORCH screening?
1. The production of IgG or IgM in the body is a rapidly changing process when initial infection or recurrent infection occurs during pregnancy, and can only be detected by quantitative analysis of concentration changes.
2.Quantitative analysis helps to detect false-positive or false-negative results.
3, For those pregnant women who have not had a basic immune status assessment before pregnancy, choosing two time points (T1, T2) to detect IgG or IgM concentration (C1, C2) and calculating the gradient of concentration change per unit time can effectively detect the specific immune response of the organism due to viral attack, but there is no reference value yet, and the more common one is C2/C1 > 4 times. All this must be predicated on quantitative detection.