The diagnosis of toxoplasmic encephalitis by polymerase chain reaction

The nested polymerase chain reaction (PCR) and the loop-mediated isothermal amplification (LAMP) assay were performed to detect and identify toxoplasma parasites in human cerebrospinal fluid (CSF). The performed nested PCR targeting the 18S rDNA using primers generated by Dr. L.D. Sibley instead of the conventionally used primers that target the B1 gene. Toxoplasma gondii-specific LAMP primers targeting both genes were also designed. The clinical sensitivity and specificity were evaluated using clinical CSF samples from 16 patients with toxoplasmic encephalitis (TE) and from 12 patients with other diseases. The 18S rDNA nested PCR showed the highest detection sensitivity limit with a minimum of 1.0 × 10^-8 ng/μl. However, sensitivity and specificity of nested PCR with clinical specimens were 50% and 100%, respectively. The sensitivity of molecular diagnosis of TE is not sufficient; therefore, patients clinically suspected of having TE should be treated promptly. This molecular diagnostic tool would restrictively facilitate a definitive diagnosis of TE at an early stage in approximately 50% of patients.