Toxoplasmosis in immunocompromised patients is a serious, life-threatening condition that requires rapid, appropriate treatment. Diagnosis is based on PCR, notably on blood samples. Systematic blood screening is carried out for patients most at risk, to detect the disease at an early stage. Detection of parasite DNA in blood in asymptomatic patients is possible, in the absence of Toxoplasma multiplication. It has previously been proposed a distinction of two entities: toxoplasmosis disease (clinical, biological and imaging evidence of toxoplasmosis) and toxoplasmosis infection (positive PCR in the blood in the absence of clinical or radiological evidence, without progression to toxoplasmosis). Since the clinical signs of toxoplasmosis are often aspecific, a positive PCR may be the first warning result, making it difficult to determine whether the patient will progress to toxoplasmosis disease or toxoplasmosis infection.

In collaboration with the French National Reference Center for toxoplasmosis, we are proposing a retrospective multicenter study to identify possible clinical, biological or imaging criteria pointing to toxoplasmosis disease or toxoplasmosis infection as soon as the first T. gondii PCR result is positive in the blood.

Inclusion Criteria:

• T. gondii positive-PCR in blood during the study period: no symptoms of toxoplasmosis since the last systematic PCR negative in blood and no history of T. gondii positive-PCR in any biological matrix for 6 weeks.

Exclusion Criteria:

• pre-analytical or analytical error leading to a false-positive result
• unknown toxoplasmosis immune status or non-immune subject
• serology in favor of acute toxoplasmosis
• congenital toxoplasmosis, ocular toxoplasmosis, toxoplasmosis in the context of HIV/AIDS
• patient opposition

-patient care at one of the participating centers