Laboratory Studies
Routine laboratory screening in chorioretinitis (CR) includes the following:
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Complete blood cell (CBC) count and platelet count: Depression of all 3 lines (ie, erythrocytes, white cells, platelets) implies an infection that causes bone marrow suppression, which may be seen with congenital infections. Platelet count can be low in patients with some viral infections or intravascular coagulation.
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Liver function tests: Measure alanine aminotransferase, aspartate aminotransferase, gamma-glutamyltransferase, alkaline phosphatase, bilirubin (total, direct, and indirect), albumin, and total protein levels. Also obtain activated partial thromboplastin time and prothrombin time. All or some of these measurements can be abnormal in most congenital infections.
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Renal function tests: Assess creatinine and blood urea nitrogen (BUN) levels. Urinalysis can be helpful in the detection of hematuria or casts.
Herpes simplex virus (HSV) types I and II, Epstein-Barr virus (EBV), varicella, and human immunodeficiency virus (HIV) are elicited by cultures or polymerase chain reaction (PCR) of blood, cerebrospinal fluid (CSF), or tissues. Immunoglobulin titers (immunoglobulin [Ig]G) from CNS fluid, serum, and other body fluids (particularly in a newborn) are of uncertain value, except for screening purpose in HIV vertical infection, toxoplasmosis, and West Nile virus infection. Positive values in a newborn may represent passive transfer of maternal antibody.
Congenital rubella can infect infants of nonimmune individuals and is diagnosed by interpreting results of viral culture and IgM and IgG titers in both infants and mothers.
Cytomegalovirus (CMV) is shed in the urine of infants who are congenitally infected, and diagnosis is indicated by positive urine culture results in infants younger than 3 weeks. In immunodeficient hosts, a CMV antigenemia test using a peripheral blood sample is helpful in establishing recurrence or infection. The CMV antigenemia uses immunofluorescent assay on buffy coat polymorphonuclear cells to detect CMV-infected cells. CMV-PCR is also being increasingly used, although at the present time its interpretation in congenital infection remains unclear.
Toxoplasma species are detected by specific IgA, IgM, IgG, Sabin-Feldman dye test, and PCR. Document Toxoplasma status of pregnant women and individuals who are immunocompromised.
Lyme disease is detected by using PCR assay of CSF and serum. The presence of specific IgM and IgG on Western blot result of serum may be significant for diagnosis and staging of infection.
Yersinia species are detected by special stool culture and acute and convalescent IgG titers.
Syphilis is detected by using serology tests (eg, nontreponemal rapid plasma reagent, Venereal Disease Research Laboratory test in CSF) and specific treponemal tests (eg, fluorescein treponemal antibody absorption, microhemagglutination-Treponema pallidum).
Mantoux skin test, acid-fast stain, and cultures of bronchial washings or biopsy samples of tissues detect M tuberculosis (MTB). MTB-PCR is available in many reference laboratories to detect the presence of MTB from biopsy and tissue samples, blood, and CSF. The QuantiFERON tuberculosis (TB) test, which measures lymphocyte interferon response to TB antigen, may aid in the diagnosis of TB.
Toxocariasis serology can be tested by using an enzyme-linked immunoabsorbent assay (ELISA) and confirmed by using a specific Western blot (available from the Centers for Disease Control and Prevention [CDC]).
Several serology tests for catscratch disease have been developed, including indirect immunofluorescent antibody (IFA) testing, which shows good correlation with strict clinical criteria. Demonstration of rising IgG titer provides the best evidence of infection.
Baylisascaris tests can be performed using serum and CSF. ELISA and Western blot are available from the Department of Veterinary Pathobiology at Purdue University.
Nitroblue tetrazolium test (or flow cytometry with dihydrorhodamine) is used to detect chronic granulomatous disease (CGD). In a healthy host, 95% or more of neutrophils produce superoxide radicals. In a host with a typical X-linked CGD, fewer than 5% of neutrophils have such ability.
Vertical HIV infection is suggested by hypergammaglobulinemia and a depressed CD4+ T-cell count. An HIV DNA PCR of the newborn can be used to confirm diagnosis of HIV infection in the presence of maternal antibodies. Testing with DNA PCR should be done when the infant is aged 2 weeks, 1 month, and 4 months in all infants at risk for vertical HIV infection.
Some experts also recommend obtaining an HIV DNA polymerase chain reaction test at birth. For children aged 18 months and older, an HIV antibody test should be used.
Imaging Studies
A pediatric ocular imaging system (RetCam3) may be used in newborns, infants, and uncooperative children.
Perform sonography, CT scanning, and/or MRI of the CNS or specific organs in patients in whom congenital infections are suspected or in an immunocompromised host.
Perform chest radiography, CT scanning, or both in patients in whom TB or sarcoidosis is suspected. CT scanning is helpful in identifying sites on which to perform biopsy for diagnostic purposes.
Perform CT scanning of the abdomen for hepatic or splenic dissemination of disease.
Perform radiography or bone scanning of the skeleton in patients in whom syphilis is suspected.
Perform echocardiography in patients with congenital rubella infection.
Other Tests
Perform a skin biopsy for rare cases of dermal hematopoiesis (blueberry muffin infant syndrome) in patients in whom congenital CMV or congenital toxoplasmosis (CTP) is suspected.
Chorioretinitis is usually diagnosed using ophthalmologic examination and not using histologic findings of the retina. However, evidence of lymphocytic infiltrations and exudates characteristic of vasculitis is found in many sites.
Granulomatous changes can be evident in biopsy samples of lymph nodes, liver, or spleen in histoplasmosis, sarcoidosis, and tuberculosis. Fungal elements are rarely found in biopsy or postmortem samples.
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Chorioretinitis in a patients with acquired immunodeficiency syndrome (AIDS).
