Optimization of PCR Technique to Assess Parasitological Response for Patients With Chronic Chagas Disease
Condition: Chagas Disease
MeSH terms: Chagas Disease
Study type: Interventional
Phase: Phase 4

Summary: 
      The purpose of this study is to estimate the gain in sensitivity of several multiple-sample
      strategies of PCR samples with respect to the current standard (single sample of 10 ml) to
      detect Chagas chronic stage at baseline and to identify the optimal sampling strategy based
      on the sensitivity, cost,the completeness of sampling and the acceptability for study
      patients.
    

Detailed description: 
      Chagas Disease (CD) ranks among the world's most neglected diseases. In Latin America, 21
      countries are endemic for CD with an estimated 108 million people at risk of contracting the
      disease. Estimates from the 1980s indicated that some 16 -18 million individuals were
      infected. In the 1990s, after a series of multinational control initiatives, estimates of the
      number of infected people were revised to 9.8 million in 2001. The estimated burden of
      disease in terms of disability-adjusted life years (DALYs) declined from 2.7 million in 1990
      to 586,000 in 2001. Recent estimates from Pan-American Health Organization (PAHO), 2006
      indicate 7.54 million infected people and 55,185 new cases per year. CD,also known as
      American trypanosomiasis,is a zoonotic disease caused by the protozoan hemoflagellate
      Trypanosoma cruzi that is mainly transmitted by large, blood-sucking, reduviid bugs of the
      subfamily Triatominae. Clinically, human CD has two phases, acute and chronic. The acute
      phase, which lasts a few weeks, is a febrile and toxemic illness, during which the parasite
      can be detected by direct examination of fresh blood. In the chronic phase, the diagnosis
      depends on hemocultures of varying degree of sensitivities, xenodiagnosis, PCR or detecting
      IgG antibodies. Untreated, the chronic phase continues for the rest of a person's life. It
      begins with no specific symptoms or clinical manifestations for a period of approximately 10
      or 15 years, the "indeterminate form" of the disease. About 20 to 50% of chronic Chagas
      patients over the ensuing years, depending on the endemic area analyzed, will develop
      involvement of the heart or gastrointestinal tract. Current therapy for CD is limited to two
      nitroheterocyclic drugs, Nifurtimox and Benznidazole, the later being the most widely used
      drug for Chagas disease treatment. The indications for treatment are acute disease (including
      congenital infection), and early chronic disease (that is, in children < 15 years of age and
      patients in the early phase of chronic infection), plus reactivation of the infection by
      immunosuppression.

      Late chronic phase is treated at the clinician's discretion. In a hierarchy of need, it has
      been argued that patients in the indeterminate phase of the disease would represent the main
      target population for evaluation of new treatments. With decreasing incidence of the disease,
      even in countries with the highest number of new cases, the highest disease burden is among
      patients in the asymptomatic, chronic phase of the disease. Bolivia, for example, has at
      least 200,000 children under the age of 15 years and 1 million adults infected with T. cruzi,
      for an estimated total of 700,000 people with the indeterminate form or asymptomatic, chronic
      phase. The development of effective and affordable treatment for the millions of people with
      ongoing infections and the prevention of chronic complications is recognized as a key disease
      control priority in CD. The evaluation of cure is considered the most complex aspect of
      treatment in CD, leading to often diverse and controversial results. The term parasitological
      cure is of difficult interpretation and the evaluation challenging, in light of the need for
      total elimination of parasites not only from blood but also from tissue. Clinical cure
      demands long-term evaluation and is often of uncertain nature due to the pathogenesis of the
      disease, with the action of the parasite, the host response and their consequent clinical
      manifestations evolving for long period of times. Over recent years an increasing body of
      data has pointed to a strong biological rationale for the use of parasitological outcomes as
      surrogate markers for acute and indeterminate Chagas disease. There is increasing evidence of
      the role of T. cruzi persistence in the perpetuation of immune response and evolution of the
      disease. Also, recent non-randomized clinical trials with long-term follow-up have
      demonstrated a positive effect from anti-parasitic chemotherapy in patients with chronic CD
      and the correlation of these findings with serology results. Therefore, for the purposes of
      clinical development and proof-of-concept, it has been suggested that parasitological and
      serological tests be used for the assessment of response in both acute and chronic disease. A
      negative direct smear at the end of treatment is generally accepted as evidence of response
      in acute patients. In chronic disease, serial hemoculture, xenodiagnosis or PCR can be used
      to support serological assessment and a positive parasitological result indicates treatment
      failure. Hemoculture and xenodiagnosis are techniques that may present low sensitivity in
      chronic patients, they require proper resources/infrastructure and very skilful personnel. In
      regards to conventional serology, with indeterminate chronic patients, a decrease in antibody
      titers may take up to 5 years with seroconversion to negative occurring after 5-10 years. In
      consequence, it is proposed that efficacy assessment for clinical studies in indeterminate
      disease be done with the use of qualitative and quantitative PCR. However, there has been
      significant variability in the clinical sensitivity and specificity of PCR in published
      studies, with differences seen across phases of the disease and a number of techniques in use
      requiring standardization. In particular, there has been concern regarding the sensitivity of
      PCR in chronic Chagas disease due to the low levels of circulating parasites and natural
      fluctuations of the parasitaemia. Latest studies have shown a broad dynamic range for PCR use
      allowing direct measurements in cases with high parasitic loads such as immunosuppressed
      Chagas disease patients and congenitally infected newborns, as well as in cases with low
      parasitaemias, such as patients at the indeterminate phase or under etiological treatment.
      PCR testing has also been used for early detection of T. cruzi reactivation after heart
      transplantation, with documented detection of parasitic load increase, previous to diagnosis
      of clinical reactivation. In addition, there are accruing clinical and experimental data
      suggesting a degree of correlation between parasitaemia and tissue infection. Another
      important advance in recent years has been the TDR sponsored-study for standardization and
      laboratory validation of qualitative PCR testing for T. cruzi. Standardized procedures for
      qualitative assessment of PCR (standard and real-time PCR) yielding higher analytical
      sensitivity and specificity, reproducibility, with low levels of intra- and inter-assay
      variation and accuracy have been selected. Results from this exercise have been presented in
      a meeting in Buenos Aires, Nov 08, and they are expected to be published in the near future.
      However, there is limited information on the efficacy of treatment for chronic indeterminate
      CD patients, and only a few studies employed PCR to assess parasitological response. A panel
      of experts in CD at three meetings hosted by DNDi and the CD protocol development team gave
      support to the evaluation of PCR as a marker for parasitological response in indeterminate
      chronic disease. During these discussions,there was consensus on the value of using serial
      blood collections for qualitative PCR assays in order to increase PCR testing sensitivity.

      Data in support of this information are limited to an Argentinean cohort of 41 pregnant women
      followed-up with monthly blood collections. In this small group, PCR sensitivity was 60,2%
      for a single collection, 74% for 2 blood collections and 80,5% for 3 blood collections (A.
      Schijman, manuscript in preparation). In addition, a study from Castro published in 2002
      indicated a significant increase from 70.0% to 81.7% in the sensitivity of PCR with the
      addition of a second sample (P=0.03). The addition of a third sample led to non-significant
      increase in sensitivity to 86.7%. Unfortunately, the sample size was small, there was no
      indication of the interval of sampling and the qualitative PCR technique was
      non-standardised. During the panel discussions, there was no agreement on the precise
      interval for serial sampling, in view of the lack of information in support for a definite
      interval for blood sampling to maximize sensitivity. Data obtained with xenodiagnosis suggest
      the absence of both circadian rhythm and T. cruzi periodicity with in chronic chagasic
      individuals. Therefore, when defining sampling procedures, one would need to balance the gain
      on the PCR sensitivity and logistics/feasibility in conducting clinical trials in a field
      setting. In order to prepare for future clinical trials on CD, DNDi acknowledges the need to
      evaluate and optimize the procedures for PCR implementation as a tool of parasitological
      assessment in patients with chronic indeterminate form of CD. Study ethical approval will be
      sought from the Médecins Sans Frontières Ethical Review Board and, the Ethical Review Board
      from the Colectivo de Estudios Aplicados y Desarollo Social (CEADES), Cochabamba, Bolivia.
      Furthermore, the study will be submitted and reviewed by the National Chagas Control Program
      and the 'Comité de Ética e Investigación' del Ministerio de Salud, Bolivia. This is a
      descriptive study aiming to assess whether multiple PCR blood sampling procedures at baseline
      can provide higher sensitivity compared to single sampling, as well as their feasibility in a
      field setting. Blood sampling for baseline and EOT will be as follows: one initial blood
      sample of 10 mL (Sample 1), followed by 1 blood sample of 5mL collected immediately following
      (Sample 2); plus one blood sample of 10mL collected 1 week later (Sample 3). Total of 3 blood
      samples. At the 6 and 12 months follow-up visits, only the optimal sampling strategy at EOT
      will be used.

      Sampling strategies:

      In order to explore PCR sensitivity according to the number of blood samples, PCR results
      will be analyzed as single assays as well as, at the data analysis stage, by combining PCR
      results for patients at a given time-point.

        -  Reference to be used Current strategy (CS): Sample 1 : Single sample of 10 ml Two major
           types of strategies may be developed and need an assessment:

        -  Reinforcement Strategy (RS) that consists in adding blood sampling(s) to the current
           single-sample approach (volume of 10 ml). Unless additional samplings do not allow the
           detection of additional PCR-positive cases (which is unlikely) such strategy will
           inevitably be more sensitive than the current one.

        -  Substitution Strategy (SS) that consists in replacing the current approach (sample 1 =
           10 ml) by a 5 ml sampling (sample 2) and possibly further sampling(s) (sample 3). These
           strategies are not necessarily better than the current one.

      Study Site:

      The present study will be conducted in rural communities in the municipalities of Aiquile,
      Omereque and Pasorapa in the province of Narciso Campero, Bolivia, where Médecins Sans
      Frontières has established a program for "Chagas disease prevention, diagnosis and treatment"
      in partnership with the local health authorities. The local population is ~ 40,000
      individuals, living in one of the areas with highest burden of CD in the country. In the
      context of this program, the individuals living in rural communities will be screened for
      Chagas disease and those who fulfil eligibility will be invited to participate in the study.
      Equal opportunities for treatment and management of the disease will be provided by MSF and
      its partners to all Chagas positive subjects, despite participation or not in the study.

      Main Entry Criteria:

      Inclusion / Exclusion Patients with chronic CD that have the indication for treatment with
      benznidazole. Patients must fulfil the following eligibility criteria for enrolment in the
      study:

      Inclusion criteria:

        -  Age between > 18 - 60 years

        -  Diagnosis of T. cruzi infection by Chagas serology. Two out of three serological tests
           must be positive (conventional ELISA, recombinant ELISA, or HAI)

        -  Written informed consent form

      Exclusion criteria:

        -  Women in reproductive age who have a positive pregnancy test at screening, or who are
           breastfeeding Note: Women in reproductive age must accept to use a contraceptive method
           during the entire treatment phase of the trial

        -  Current presentation of serious health condition such as: active pulmonary tuberculosis
           and clinical signs of liver or renal failure.

        -  Chagas cardiomyopathy stage II, III and IV (according to the NYHA classification)

        -  Subjects requiring pacemaker implantation or other serious cardiac conduction defects

        -  History of CD treatment with benznidazole or nifurtimox at any time in the past

        -  Inability to comply with follow-up and/or not having a permanent address

        -  History of alcohol abuse or any other drug addiction Note: all patients participating in
           this study will be treated with Benznidazole, 5mg/Kg/day PO BID for 60 days, as per
           routine care provided by MSF in rural communities in Aiquile. This treatment is in
           accordance with the local recommendations from the Ministerio de Salud y Deportes de
           Bolivia. The participation of the patient in this study is voluntary and his refusal or
           withdrawal of consent at any time during the study will not affect his/her right to
           receive treatment for Chagas disease.
    

Intervention name(s): Benznidazole
Intervention type(s): Drug
Intervention description(s): All patients participating in this study will be treated with Benznidazole, 5mg/Kg/day PO BID for 60 days with a maximum daily dose of 300mg, as per routine care provided by MSF in rural communities in Aiquile. For patients > 60 kg, the total dose should be calculated (5mg/Kg x Weight x 60 days) and treatment duration should be adjusted/prolonged accordingly. This treatment is in accordance with the local recommendations from the Ministerio de Salud y Deportes de Bolivia.
Other intervention name(s): LAFEPE Benznidazol
Intervention MeSH terms: Benzonidazole
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Diagnostic
Keywords: Chagas Disease; PCR; diagnosis