Diagnosis of Perinatal TORCH Infections

Maternal viral and protozoan infections contribute enormously to childhood morbidity. TORCH infections include infections associated with Toxoplasma, Other organisms (Parvovirus, human immunodeficiency virus, Epstein-Barr virus, herpesviruses 6 and 8, varicella, syphilis, enteroviruses), Rubella, Cytomegalovirus (CMV), and Hepatitis. Despite the recent emphasis in the screening, antibiotic prophylaxis, and management of early-onset group B streptococcal sepsis of the newborn (GBS sepsis), many neonates and children yearly experience the consequences of classic perinatal infections (Table 1). These infections need the same attention as GBS sepsis. The other TORCH infections such as rubella, varicella, Epstien-Barr virus, herpesvirus 6 and 8, and hepatitis B (HBV) will receive little discussion in the remainder of this article as their diagnosis and management is clear and highly efficacious.TABLE 1: Perinatal Infections and Newborn/Childhood Disease The reasons for the lack of focus on TORCH infections are speculative and include few maternal symptoms of infection, limited and expensive diagnostic tools for fetal infection, lack of effective therapy in the treatment of these infections, and the late occurrence of symptoms in children (chorioretinitis, deafness, mental deficiencies). In contrast, GBS sepsis can be prevented through risk identification, screening for maternal lower genital tract GBS carriage, and relatively inexpensive antibiotic prophylaxis. The incidence of subclinical infection in the mother is >95% with CMV, toxoplasmosis, hepatitis B, Parvovirus B19, Epstein-Barr virus, herpesvirus type six and 8, group B streptococcus, and HIV; and 50-75% with varicella, herpes simplex virus (HSV), and syphilis. How does the obstetrician identify the fetus at risk for perinatal infection from the latter three organisms? Currently, prenatal patients are routinely screened for rubella, hepatitis B, syphilis, GBS, and HIV. These infections have clear measures to prevent or limit perinatal infection by vaccine, immunoglobulins, or antibiotics. Varicella soon may join the latter group by virtue of a newly developed, effective vaccine. The efficacy of these therapies exceeds 90%. In the United States, routine screening for other TORCH infections does not seem to be justified based on cost-benefit analysis (see Chapter by Mittendorf). The central issue related to prenatal diagnosis is the inability to diagnose maternal infection. The obstetrician must base his or her laboratory evaluation on the presence of epidemiologic risk factors or on the presence of clinical findings. Table 2 describes epidemiologic and clinical risk factors that increase the likelihood of perinatal infection.TABLE 2: Epideminologic and Clinical Risk Factors for Perinatal Infection Occupational exposure includes work in the following settings: chronic care facilities, day care facilities, neonatal intensive care units, renal dialysis units, and elementary schools (Parvovirus B19). The major benefit of risk identification that the prevalence of infection will be higher in the tested population. This can have a tremendous effect on the accuracy of the test. For example, given a test that is 90% sensitive and 95% specific, the incidence of false-positive tests is 98% when the prevalence is 1 per 1,000, 85% when the incidence is 1 per 100, and 31% when the incidence is 1 per 10. Because evidence of fetal infection on initial screening raises the specter of complicated and dangerous fetal diagnosis (cordocentesis) or elective abortion, testing accuracy is paramount to reduce the number of fetuses who are unnecessarily injured by such techniques. A corollary is that clinicians must carefully educate the pregnant woman before and after a screening test. The purpose of this article is not to describe the accuracy of testing in the setting of a world-class laboratory, but to describe the accuracy of tests provided by the major clinical laboratories in the United States. Major commercial laboratories include LabCorp, SmithKline-Beecham, and Specialty Laboratories. The efficiency of the tests and the laboratories determines further testing or intervention. As argument is developed, the most prudent action may be not to start with routine screening in the first place.