Diagnosis of congenital toxoplasmosis by using a whole-blood gamma interferon release assay.

Congenital toxoplasmosis in newborns is generally subclinical, but infected infants are at risk of developing ocular lesions. Diagnosis at birth relies mainly on serological tests. Cell-mediated immunity plays the major role in resistance to infection but is not routinely investigated for diagnostic purposes. Here, we describe a simple test based on the gamma interferon (IFN-gamma) response after stimulation of whole blood by crude parasitic antigens. One milliliter of heparinized blood was centrifuged; plasma was kept for routine serological tests, and pellets were resuspended in culture medium. After 24 h of culture in the presence of crude Toxoplasma gondii antigen, the cells were centrifuged and the supernatant was assayed for IFN-gamma. For 62 infants under 1 year of age born to mothers who were infected during pregnancy, the sensitivity and specificity of the test were 94% (with positive results for 16 of 17 infected infants) and 98% (with negative results for 44 of 45 uninfected infants), respectively. The false-negative result was for a treated baby who gave positive results after the withdrawal of treatment. The false positive was obtained for a 3-month-old baby. For a cohort of 124 congenitally infected patients between 1 and 30 years of age, the sensitivity of the assay was 100%. We present a simple test based on IFN-gamma secretion to assess cell-mediated immunity in toxoplasmosis. As only 1 ml of blood is required to investigate humoral and cellular immunity, our assay is well adapted for the study of congenital toxoplasmosis in infants. Using purified antigens or recombinant peptides may improve the test performance.

Automated Plasmodium detection by the Sysmex XN hematology analyzer.

BACKGROUND: Malaria is a potentially severe disease affecting nearly 200 million people per year. Early detection of the parasite even in unsuspected patients remains the challenging aim for effective patient care. Automated complete blood counts that are usually performed for any febrile patient might represent a tool to ascertain malaria infection. AIMS: To evaluate the ability of the new generation of the Sysmex hematology analyzer (XN-series) to detect malaria. METHODS: We retrospectively studied 100 blood samples performed with the recent Sysmex XN analyzer that were positive for Plasmodium and explored its ability to detect the parasite. 100 samples from patients uninfected by malaria were used as control group. RESULTS: Specific abnormalities such as additional events in the mature neutrophil/eosinophil area of the white blood cells differential (WDF) scattergram were noted for 1.1% of Plasmodium falciparum samples and 56.2% of other Plasmodium species samples. Mature parasite stages (schizonts or gametocytes) were observed on blood smears among those samples. WDF scattergrams were able to detect 80.0% (12/15) of Plasmodium mature stages. Furthermore, the differential in white blood counts between WDF and white cell nucleated (WNR) channels was a predictive signal of Plasmodium mature stages in 73.3% (11/15) of samples and may be explained by a differential destruction of particles with the analyzer reagent. CONCLUSION: Associated to thrombocytopaenia, a Sysmex XN Plasmodium pattern may represent a useful warning for Plasmodium detection in unsuspected patients, particularly when mature parasite stages are present.