Juan David Ramírez

Dr. Juan David Ramírez

orcid

Research Focus & Metrics

Academic Career Length

18Years (2009-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

View All Publications
11 January 2011 in PLOS Neglected Tropical Diseases
Verified
Journal Article
Open access
PDF file
ASAlejandro Schijman
Alejandro Schijman
MBMargarita Bisio
Margarita Bisio
LOLiliana Orellana
Liliana Orellana
MSMariela Sued
Mariela Sued
TDTomás Duffy
Tomás Duffy
JLJanis Ladzins
Janis Ladzins
A century after its discovery, Chagas disease still represents a major neglected tropical threat. Accurate diagnostics tools as well as surrogate markers of parasitological response to treatment are research priorities in the field. The purpose of this study was to evaluate the performance of PCR methods in detection of Trypanosoma cruzi DNA by an external quality evaluation. An international collaborative study was launched by expert PCR laboratories from 16 countries. Currently used strategies were challenged against serial dilutions of purified DNA from stocks representing T. cruzi discrete typing units (DTU) I, IV and VI (set A), human blood spiked with parasite cells (set B) and Guanidine Hidrochloride-EDTA blood samples from 32 seropositive and 10 seronegative patients from Southern Cone countries (set C). Forty eight PCR tests were reported for set A and 44 for sets B and C; 28 targeted minicircle DNA (kDNA), 13 satellite DNA (Sat-DNA) and the remainder low copy number sequences. In set A, commercial master mixes and Sat-DNA Real Time PCR showed better specificity, but kDNA-PCR was more sensitive to detect DTU I DNA. In set B, commercial DNA extraction kits presented better specificity than solvent extraction protocols. Sat-DNA PCR tests had higher specificity, with sensitivities of 0.05–0.5 parasites/mL whereas specific kDNA tests detected 5.10−3 par/mL. Sixteen specific and coherent methods had a Good Performance in both sets A and B (10 fg/µl of DNA from all stocks, 5 par/mL spiked blood). The median values of sensitivities, specificities and accuracies obtained in testing the Set C samples with the 16 tests determined to be good performing by analyzing Sets A and B samples varied considerably. Out of them, four methods depicted the best performing parameters in all three sets of samples, detecting at least 10 fg/µl for each DNA stock, 0.5 par/mL and a sensitivity between 83.3–94.4%, specificity of 85–95%, accuracy of 86.8–89.5% and kappa index of 0.7–0.8 compared to consensus PCR reports of the 16 good performing tests and 63–69%, 100%, 71.4–76.2% and 0.4–0.5, respectively compared to serodiagnosis. Method LbD2 used solvent extraction followed by Sybr-Green based Real time PCR targeted to Sat-DNA; method LbD3 used solvent DNA extraction followed by conventional PCR targeted to Sat-DNA. The third method (LbF1) used glass fiber column based DNA extraction followed by TaqMan Real Time PCR targeted to Sat-DNA (cruzi 1/cruzi 2 and cruzi 3 TaqMan probe) and the fourth method (LbQ) used solvent DNA extraction followed by conventional hot-start PCR targeted to kDNA (primer pairs 121/122). These four methods were further evaluated at the coordinating laboratory in a subset of human blood samples, confirming the performance obtained by the participating laboratories. This study represents a first crucial step towards international validation of PCR procedures for detection of T. cruzi in human blood samples. A century after its discovery, Chagas disease, caused by the parasite Trypanosoma cruzi, still represents a major neglected tropical threat. Accurate diagnostics tools as well as surrogate markers of parasitological response to treatment are research priorities in the field. The polymerase chain reaction (PCR) has been proposed as a sensitive laboratory tool for detection of T. cruzi infection and monitoring of parasitological treatment outcome. However, high variation in accuracy and lack of international quality controls has precluded reliable applications in the clinical practice and comparisons of data among cohorts and geographical regions. In an effort towards harmonization of PCR strategies, 26 expert laboratories from 16 countries evaluated their current PCR procedures against sets of control samples, composed by serial dilutions of T.cruzi DNA from culture stocks belonging to different lineages, human blood spiked with parasite cells and blood samples from Chagas disease patients. A high variability in sensitivities and specificities was found among the 48 reported PCR tests. Out of them, four tests with best performance were selected and further evaluated. This study represents a crucial first step towards device of a standardized operative procedure for T. cruzi PCR.

1 October 2016 in Cell
Verified
Journal Article
Closed access
ACAleksey Chudnovskiy
Aleksey Chudnovskiy
AMArthur Mortha
Arthur Mortha
VKVeronika Kana
Veronika Kana
AKAndrea Kennard
Andrea Kennard
JRJuan David Ramírez
Juan David Ramírez
MMMiriam Merad
Miriam Merad

1 March 2014 in Infection, Genetics and Evolution
Verified
Journal Article
Closed access
JRJuan David Ramírez
Juan David Ramírez
LSLaura Viviana Sánchez
Laura Viviana Sánchez
DBDiana Carolina Bautista
Diana Carolina Bautista
ACAndrés Felipe Corredor
Andrés Felipe Corredor
AFAstrid Carolina Flórez
Astrid Carolina Flórez
CSChristen Rune Stensvold
Christen Rune Stensvold

1 September 2015 in The Journal of Molecular Diagnostics
Verified
Journal Article
Closed access
JRJuan Carlos Ramírez
Juan Carlos Ramírez
CCCarolina Inés Cura
Carolina Inés Cura
FCFundação C. Cruz
Fundação C. Cruz
ELEliane Lages-Silva
Eliane Lages-Silva
NJNatalia Juiz
Natalia Juiz
ASAlejandro Schijman
Alejandro Schijman

1 July 2016 in Infection, Genetics and Evolution
Verified
Journal Article
Closed access
JRJuan David Ramírez
Juan David Ramírez
ASAngie Sánchez
Angie Sánchez
DCDiana Carolina Hernandez Castro
Diana Carolina Hernandez Castro
CFCarolina Flórez
Carolina Flórez
MBMaría Consuelo Bernal
María Consuelo Bernal
RCRodolfo D. Casero
Rodolfo D. Casero

13 July 2022 in Travel Medicine and Infectious Disease
Verified
Journal Article
Closed access
NLNicolas Luna
Nicolas Luna
ARAngie L. Ramírez
Angie L. Ramírez
MMMarina Muñoz
Marina Muñoz
NBNathalia Ballesteros
Nathalia Ballesteros
LPLuz H. Patiño
Luz H. Patiño
JRJuan David Ramírez
Juan David Ramírez