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Repeat testing can distinguish between true and false serology. remained essentially unchanged 15C78 days after the positive serum sample. An additional eight patients treated with IVIG for various conditions were evaluated prospectively. All Rabbit Polyclonal to ACOT1 were seronegative one day pre-IVIG infusion, five patients demonstrated an increase in the IgG titers one to three days after IVIG administration, one interpreted as positive and four as intermediate, whereas three patients remained seronegative, Panaxtriol suggesting that false seropositivity after IVIG therapy may not occur in all patients. Treatment with IVIG can result in false-positive serology for Increased awareness to the misleading impact of IVIG is usually warranted to avoid misinterpretation. Repeat testing can distinguish between true and false serology. Preserving serum samples prior to IVIG administration is usually suggested. culture from affected lymph nodes is usually rarely positive, and growth, if occurs, may require up to four weeks of incubation; Warthin Starry silver stain is usually of low sensitivity and inadequate specificity; cytology and histopathology are not specific; immunohistochemical assay is not available in routine diagnostic laboratories, and polymerase chain reaction (PCR), Panaxtriol although sensitive and specific, requires tissue or pus specimens from involved tissue, which are not commonly available [3]. Serological assays, both immunofluorescent antibody (IFA) test and enzyme immunoassay (EIA), for detection of anti-antibodies have become the most commonly used diagnostic assessments for CSD, both as in-house and commercial products. One of the several limitations of CSD serology is the frequent lack of anti-IgM, even in documented acute contamination. Hence, the majority of CSD cases are diagnosed based on the presence of anti-IgG [3,8]. Intravenous immunoglobulin (IVIG) has become a relatively common treatment for immune-mediated and inflammatory diseases and primary or secondary immunodeficiency says [9]. Interference with serological testing of IgG antibodies is usually a recognized, though not well characterized, phenomenon after administration of immunoglobulin and there are a number of reports describing false-positive serological testing with potential misleading diagnoses of infectious disease following IVIG administration [10,11,12,13,14,15,16]. In the present study, we report for the first time a mistaken diagnosis of common and atypical CSD in patients with clinical presentations consistent with CSD due to false-positive serological testing following therapy with IVIG and present an approach to avoid an incorrect diagnosis. 2. Results The following representative cases illustrate the clinical quandary about serodiagnosis of CSD following treatment with IVIG. Case 1, IVIG given for encephalitis. A previously healthy eight-year-old female was hospitalized because of fever and cough of two weeks duration with no response to oral amoxicillin. The patient owned a kitten with whom she used to play frequently. On admission she was febrile and tachypneic, chest x-ray revealed unilateral pneumonia and intravenous ceftriaxone was started. On the third day of admission, her temperature increased to 39.7 C and she became sleepy and irritable with nuchal rigidity. She later became comatose, was intubated, and transferred to the pediatric intensive care unit. Blood leukocyte count was 27,600/mm3, cerebrospinal fluid showed a leukocyte count of 138/mm3 with 66% mononuclear cells, protein 75 mg/dL and normal glucose level. Blood and CSF cultures were sterile. Magnetic resonance imaging revealed an abnormal signal in the thalamus, basal ganglia, pons, and the fourth ventricle periventricular white matter, consistent with encephalitis. Empiric treatment included high dose ceftriaxone, acyclovir, dexamethasone, and IVIG 2 gr/kg, divided on two consecutive days. A workup for the diagnosis of a host of viral, bacterial, and fungal pathogens was unfavorable except for positive IgM and IgG serology for and positive anti-IgG antibodies at a titer of 1 1:100. Azithromycin and doxycycline were started upon receiving the positive serological results. Serology was repeated 14 days later, Panaxtriol demonstrating no change in the IgM and IgG seropositivity to and unfavorable results for IgG being positive at a titer of 1 1:100, thus meeting the diagnostic criteria of CSD. Doxycycline was commenced for seven days. A second serum specimen for serology was repeated eight days after the first one and was found negative. After 14 days of admission, the patient was.