Assessment of chemiluminescence and PCR effectiveness in relation to conventional serological tests for the diagnosis of Chagas' disease

Abstract

While testing 414 sera for the diagnosis of Chagas' disease, the conventional reactions of indirect hemagglutination, indirect immunofluorescence and the immunosorbent assay showed a sensitivity of 95.7%, 100% and 98.2% and a specificity of 98%, 98% and 96.4%, respectively, and an excellent association using Fisher's exact test. Chemiluminescence presented 100% sensitivity and 89.6% specificity, while PCR showed 100% specificity and 1.2% sensitivity. It is believed that the three conventional serological reactions are still adequate for diagnosing Chagas' disease. Key-words: Chagas' disease. Diagnosis. Serology. Chemiluminescence. PCR. Chagas' disease or American trypanosomiasis is an endemic infection of gradual evolution caused by the intracellular protozoa Trypanosoma cruzi. Diagnosis of chagasic patients has been made through parasitological and/ or serological methods like indirect hemagglutination (IH), indirect immunofluorescence (IFA) and indirect enzymelinked immunosorbent assay (ELISA). Other reactions such as chemiluminescence 1 , agglutination in gel 12 , lysis mediated by complement 8 and trans-sialidase inhibition 3 10 can be used. Chemiluminescence has not, however, been used for the diagnosis of Chagas' disease as it is still being standardized. RESUMOCurrent legislation 11 recommends screening tests for Chagas' disease in blood banks, but not in laboratories, using at least two methods with different methodological principles due to the false-positive and false-negative reactions found in different methodologies. IH, IFA and ELISA are considered typical reactions and are currently used. Technical scientific advances have made new tests and methods available. The suggestion to evaluate chemiluminescence and PCR as complementary tests for introduction in laboratory routines for the diagnosis of Chagas' disease, as well as their comparison with conventional methodologies is relevant, because of the need to find out precisely what their specificity, sensitivity and efficiency are. These three aspects are of major importance as they reflect not only on the results, but also on the prospect of clarifying doubts that have been raised by 386Duarte AMV et al cross-reactions with antibodies from carriers of chronic diseases and also the confirmation of indeterminate results obtained in conventional serological reactions.A total of 414 volunteers, male and female, aged between 10 and 80 years old, residents of urban and rural areas, took part in this study, which was conducted between October 2000 and January 2002. These individuals came from the municipalities of Itabira (n = 82), ferros (n = 229) and carbonita (n = 103) in the state of Minas Gerais, Brazil. Ninety-nine individuals had characteristic symptoms of the infection, such as cardiological (n = 79), digestive (n = 15) and cardiodigestive alterations (n = 5), in addition to being seropositive. Sixty-three volunteers showed no symptoms, even though they were seropositive, and eighteen experienced no symptoms and their sera were classified a...

A Systematic Review of High Quality Diagnostic Tests for Chagas Disease

“…Although eight studies reported the manner in which they handled samples discordant by the reference standard, only four reported the number of samples which were discordant by the reference standard. In these four cases, the percentage of discordant samples out of the total was 7% (23/335) [17], 4% (40/1025) [18], 4% (17/398) [23], and 0.3% (3/999) [24]. In a study by Zicker and colleagues, results for IFA and HA were reported for all sera without specifying a clear reference standard.…”

American Trypanosomiasis in Dogs from an Urban and Rural Area of Yucatan, Mexico

“…Most of them exhibit similar solubility to DNA, and as a consequence, they are not completely removed during classical extraction protocols (Wilson 1997). The combined use of serological tests and PCR assays may diminish the number of false-negative samples as previously described (Duarte et al 2006). PCR is efficient to detect specific DNA genome of the parasite during early infections with a low possibility of being detected by serological assays.…”

“…Because of the intrinsic characteristics of each assay, the low concordance of IFA versus PCR was observed as previously reported (Jiménez-Cardoso et al 2000). For that reason, PCR is not appropriate as the sole diagnosis method, rather as a complement to serology, particularly in the case of indeterminate patients (Duarte et al 2006). In humans, the low efficiency of PCR for the specific detection of T. cruzi from blood of seropositive patients and patients with inconclusive result has been reported (Picka et al 2007); however, when PCR was used in a PCR-LIT hemoculture, seropositive cases were confirmed as well as from inconclusive cases (Picka et al 2007); the main inconvenience for the use of that methodology could be the long duration to obtain a final result.…”

Therapy, diagnosis and prognosis of chronic Chagas disease: insight gained in Argentina

“…Methods to detect the parasite's genomic fragments in tissues and body fluids using PCR have proved to be promising tools for the assessment of therapeutic effectiveness (Britto et al 1995, Solari et al 2001, Galvão et al 2003, Duarte et al 2006, Diez et al 2007). There is consensus that, even with limitation, it will be a useful tool to improve the assessment of treatment efficacy.…”