Diagnosis of toxoplasmic encephalitis in patients with acquired immunodeficiency syndrome by using a new serologic method.

The present study was performed to develop a serological method for diagnosing toxoplasmic encephalitis in patients with acquired immunodeficiency syndrome (AIDS). The trophozoite form of Toxoplasma gondii, fixed with either Formalin or acetone, was used in a modification of an agglutination method previously shown to differentiate between the acute and the chronic (latent) stages of infection with toxoplasma in immunologically normal persons. By using these antigens in separate tests and evaluating the data for statistical significance, 70% of patients with AIDS with biopsy-proven toxoplasmic encephalitis were distinguished from control, ambulatory patients with AIDS with toxoplasma antibodies but without signs or symptoms of central nervous system involvement. In a separate study, the agglutination tests identified from controls 84% of patients with AIDS with two or more brain lesions detected by computed-tomographic or magnetic-resonance-imaging scans and suspected of having toxoplasmic encephalitis. Thus, these agglutination tests should prove valuable for the noninvasive diagnosis of toxoplasmic encephalitis in patients with AIDS.