Seronegative conversion.
During the 4-year posttreatment follow-up, seronegative conversion was observed in a total of 16 (8.12%) and 8 (8.16%) patients in the 60-day and 30-day nifurtimox regimens, respectively (Number and incidence rate of seronegative conversion with nifurtimox treatment (full analysis set)Total duration of observation is the estimated actual number of years at risk for all patients who contributed to the study.The incidence rate was the number of new cases of seronegative conversion during the study period (i.e., 4 years after the end of nifurtimox treatment) divided by the patient-time at risk. It was modeled using a Poisson distribution with a two-sided 95% exact CI.CI, confidence interval.Overall, the number of new cases with seronegative conversion increased during the posttreatment follow-up. In the 60-day regimen, seronegative conversion, measured and confirmed by two types of assays (recombinant ELISA and IHA), was observed for the first time in 7 (3.55%), 3 (1.52%), 3 (1.52%), and 3 (1.52%) patients at the 1-, 2-, 3-, and 4-year posttreatment follow-up, respectively. The first observation of seronegative conversion in the 30-day nifurtimox regimen group at the corresponding follow-up time points was documented in 4 (4.08%), 1 (1.02%), 2 (2.04%), and 1 (1.02%) patients, respectively (Kaplan–Meier curves of seronegative conversion in patients receiving 60-day or 30-day nifurtimox treatment regimens (full analysis set, In an exploratory analysis of serological response by age group, the highest number of seronegative conversions occurred in those aged 2 years or younger. In this age group, seronegative conversion was observed in 13 of 30 patients (43.33%) in the 60-day regimen and 7 of 13 patients (53.85%) in the 30-day regimen, with corresponding incidence rates of 14.61 100 patients/year (95% CI: 7.78–24.98 100 patients/year) and 18.92 100 patients/year (95% CI: 7.61–38.98 100 patients/year), respectively (Seronegative conversion measured by two types of assay (recombinant ELISA and IHA) according to age 4 years after the end of nifurtimox treatment (full analysis set)Total duration of observation is the estimated actual number of years at risk for all patients who contributed to the study.The incidence rate was the number of new cases of seronegative conversion during the study period (i.e., 4 years after the end of nifurtimox treatment) divided by the patient-time at risk. It was modeled using a Poisson distribution with a two-sided 95% exact CI. Negative results for both recombinant enzyme-linked immunosorbent assay (ELISA) and indirect hemagglutination assay (IHA) were required for the patient to be considered to have achieved seronegative conversion.