Diagnosis of Toxoplasmic Lymphadenopathy: Comparison of serology and histology

Introduction: Toxoplasma gondii is a zoonotic protozoan that infects most species of birds and mammals. It can cause neurologic or ocular disease with wide ranging manifestations. Human infection is usually asymptomatic, but some may develop fever, lymphadenopathy, malaise, chills, sweats, headaches or myalgia. Presence of lymphadenopathy is considered as a positive sign of toxoplasmosis. This is confirmed by biopsy of the inflamed lymph node.Objective: The present study was carried out to determine the reliability of the histological findings in the diagnosis of toxoplasmosis.Methods: Biopsy reports of seventeen patients who presented with lymphadenopathy were studied. ELISA was carried out in serum samples of the 17 individuals. Toxoplasma IgG avidity ELISA was performed to identify the phase of infection (acute/chronic). PCR was performed to confirm the results from ELISA.Results: Six cases were found to be seropositive. However all 17 cases had a positive biopsy report. PCR was performed to detect bands specific to T. gondii but they were absent. This result was supported by Toxoplasma IgG avidity testing which revealed that all six positive samples had high avidity thus suggesting that the infection was chronic.Conclusion: The study revealed that histological findings produced 64.7 % (11/17) false positive results. Chronic infection does not have the organism in the blood stream resulting in the absence of DNA for PCR amplification which in turn explains the absence of bands specific for T. gondi. Thus it is recommended that serology (ELISA) be used to diagnose toxoplasmosis.