PCR detection of Toxoplasma gondii DNA in CSF for the differential diagnosis of AIDS-related focal brain lesions

Abstract

To evaluate whether the detection of Toxoplasma gondii DNA in CSF could contribute to the differential diagnosis of AIDS-related focal brain lesions, CSF samples from 88 HIVinfected patients (56 with focal brain lesions and 32 without) were tested prospectively by a nested PCR for the B1 gene of T. gondii. The assay had a detection limit of 10 trophozoite equivalents. Six of 18 patients with toxoplasmic encephalitis, but none of the 70 patients with other disorders, were PCR-positive (33.3% sensitivity and 100% specificity). Considering only those patients with cerebral toxoplasmosis from whom CSF was collected before or during the first week of antitoxoplasmic therapy, sensitivity rose to 50%. This was higher than the sensitivity in patients whose CSF was collected after the first week of treatment (odds ratio (OR) of 7.0; 95% CI: 0.46-218.2). The administration of antitoxoplasmic prophylaxis did not affect the PCR results. Patients with a poor response to therapy had a higher probability of detectable T. gondii DNA in their CSF (OR of 5.0; 95% CI: 0.37-86.6). All patients with other central nervous system disorders were PCR-negative. Despite the moderate sensitivity, the high specificity and positive predictive value (100%) make this assay a useful tool in the differential diagnosis of AIDS-related focal brain lesions as part of a series of CSF and neuroradiological examinations.

Diagnosis of Cerebral Toxoplasmosis in AIDS Patients in Brazil: Importance of Molecular and Immunological Methods Using Peripheral Blood Samples

“…Second, all blood samples from patients with cerebral toxoplasmosis were collected before or on day 3 of specific therapy. Previous studies reported that anti-Toxoplasma therapy decreases diagnosis sensitivity, especially if samples are collected after the first week of treatment (9). Finally, most of the studied patients with cerebral toxoplasmosis presented severe immunodeficiency (less than 200 CD4 ϩ T lymphocytes/l).…”

“…The evaluation of molecular diagnosis in cerebral toxoplasmosis is normally done in CSF samples. In general, the sensitivity of the PCR test is extremely variable (11.5 to 100%), but the specificity is high (96 to 100%) (9,11,15,29,30,36,38). Nevertheless, CSF collection is invasive and is inappropriate in a subset of patients with expansive cerebral lesions.…”

PCR Assay Using Cerebrospinal Fluid for Diagnosis of Cerebral Toxoplasmosis in Brazilian AIDS patients

“…Variations in technical procedure between different laboratories can affect PCR results (11). We believe that some conditions contributed to raise sensitivity with our PCR assay.…”

Neues bei HIV und Neuro-Aids

“…ausreichend therapierten Residualzuständen persistiert eine intrathekale Antikörpersynthese oft über Jahre. Zur Beurteilung der Krankheitsaktivität und Therapiebedürftigkeit sind daher auch nicht erregerspezifische Kriterien wie die Zellzahl und -differenzierung im Liquor sowie die Schrankenfunktion zu berücksichti-gen. Nach erfolgreicher antibiotischer Therapie sind Zellzahl und Schrankenfunktionsstörung innerhalb von Wochen bis Monaten, der VDRL und das Treponemen-IgM innerhalb eines Jahres rück-läufig [91,92]. Die zerebrale Toxoplasmose ist eine der häufigsten opportunistischen Infektionen bei Patienten mit AIDS und einer CD4 + -T-Zellzahl < 100/µl.…”

“…Die Toxoplasma-PCR hat nur geringe bis moderate Sensitivität (12 -64 %), wobei die Spezifität bei annähernd 100 % liegt. Ein negativer Befund schließt eine zerebrale Toxoplasmose nicht aus, sodass im Verdachtsfall und passender MRT-Bildgebung eine Therapie eingeleitet werden sollte [91,92].…”