Autor/a:
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Parrado, Rudy; Ramírez, Juan Carlos; Barra, Anabelle de la; Alonso-Vega, Cristina; Juiz, Natalia; Ortiz, Lourdes; Illanes, Daniel; Torrico, Faustino; Gascón i Brustenga, Joaquim; Alves, Fabiana; Flevaud, Laurence; García, Lineth; Schijman, Alejandro G.; Ribeiro, Isabela
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Abstract:
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This work evaluated a serial blood sampling procedure to enhance the
sensitivity of duplex real-time quantitative PCR (qPCR) for baseline detection and
quantification of parasitic loads and posttreatment identification of failure in the
context of clinical trials for treatment of chronic Chagas disease, namely, DNDi-CHE1224-001 (ClinicalTrials.gov registration no. NCT01489228) and the MSF-DNDi PCR
Sampling Optimization Study (NCT01678599). Patients from Cochabamba (n 294),
Tarija (n 257), and Aiquile (n 220) were enrolled. Three serial blood samples
were collected at each time point, and qPCR triplicates were tested for each sample.
The first two samples were collected during the same day and the third one 7 days
later. A patient was considered PCR positive if at least one qPCR replicate was detectable. Cumulative results of multiple samples and qPCR replicates enhanced the
proportion of pretreatment sample positivity from 54.8% to 76.2%, 59.5% to 77.8%,
and 73.5% to 90.2% in Cochabamba, Tarija, and Aiquile cohorts, respectively. This
strategy increased the detection of treatment failure from 72.9% to 91.7%, 77.8% to
88.9%, and 42.9% to 69.1% for E1224 low-, short-, and high-dosage regimens, respectively, and from 4.6% to 15.9% and 9.5% to 32.1% for the benznidazole arm in
the DNDi-CH-E1224-001 and MSF-DNDi studies, respectively. The addition of the
third blood sample and third qPCR replicate in patients with nondetectable PCR results in the first two samples gave a small, non-statistically significant improvement
in qPCR positivity. No change in clinical sensitivity was seen with a blood volume increase from 5 to 10 ml. The monitoring of patients treated with placebo in the
DNDi-CH-E1224-001 trial revealed fluctuations in parasitic loads and occasionally
nondetectable results. In conclusion, a serial sampling strategy enhanced PCR sensitivity to detecting treatment failure during follow-up and has the potential for improving recruitment capacity in Chagas disease trials, which require an initial positive qPCR result for patient admission. |