Serologic diagnosis of toxoplasmic lymphadenitis

Four different serologic tests were compared and assessed for the diagnosis of toxoplasmic lymphadenopathy. Eleven cases of lymphadenopathy were subjected to the study in which the histo-pathology of lymph nodes was consistent with toxoplasmosis. The serum specimens, with two exceptional cases, were obtained from the patients one to 4.5 months (average, 2.5 months) after onset of the disease. Seventeen cases of malignant lymphoma and 368 general outpatients served as controls. Sabin-Feldman dye test (DT) titers of ≥ 1: 1,024 were reached in all the patients with toxoplasmic lymphadenitis, and 82% of them had a titer of ≥1: 4,096. All patients with malignant lymphoma and 98% of patients with general disease showed titers of ≤1: 256. In the indirect latex agglutination (ILA) test, all the cases of toxoplasmic lymphadenitis had a titer of ≥1: 256 and 44% had ≥1: 4,096. In the control groups, less than 20% of the cases had a titer of ≥1: 256, but no case showed ≥1: 4,096. The indirect hemagglutination (IHA) test were positive at a titer of ≥1: 4,096 in 89% of cases of toxoplasmic lymphadenitis, while 13% of the control populations had ≥1: 4.096. The IgM-immunofluorescent antibody (IgM-IFA) test titers were positive at ≥1: 16 in all the cases of toxoplasmic lymphadenitis, and ≥1: 32 in 56% of them. All the patients with malignant lymphoma were negative at 1:16. Although 21% of the general outpatients showed ≥1: 16, only 4% had ≥1: 32. From these results, it was suggested that DT is the most reliable technique for the sero-diagnosis of toxoplasmic lymphadenitis. The IHA may be the least useful among these tests. The significant antibody titers for the possibility of toxoplasmic lymphadenitis are ≥1: 1,024 for DT, ≥1: 256 for ILA test, ≥1: 1,024 fo IHA test and ≥1: 16 for IgM-IFA test. The criteria with much higher titers, e.g., ≥1: 4,096 for both DT and ILA test and ≥1: 64 for IgM-IFA test makes the diagnosis more definitive, but on the other hand, it brings increasing possibility of missing the disease.