Quality assurance of the serologic diagnosis of Chagas' disease

Abstract

A quality assurance program of the Chagas' disease laboratory network of Argentina has been conducted by the National Reference Center since 1988, with the aim of assessing the reliability of serologic test results. Chagas' disease is endemic in Argentina, but the prevalence of seropositivity for Trypanosoma cruzi among 18- to 20-year-old men decreased from 5.8% in 1981 to 1.8% in 1994. About 600 laboratories form the Chagas' disease laboratory network, with main central laboratories in each of the 24 provinces in Argentina. The quality assurance program promotes regular use of good laboratory practice and internal and external quality control to improve performance of the participants; it also provides technical assistance and guidelines. Eventual corrective measures are discussed in workshops. Results of the first external evaluation by proficiency testing of serum panels and confirmation of results for 58 of the main laboratories reveal that from 1988 to 1994 the rate of agreement has increased.

Chagas disease in bone marrow transplantation: an approach to preemptive therapy

“…Those methods were standardized in the Fatala Chabe´n Institute, and sensitivity and specificity were frequently reported. 12,13 According to the WHO criteria, at least two of three specific serological tests must be reactive to consider a patient infected with T. cruzi. Additionally, all CD patients under immunosuppression for underlying diseases and therefore at risk of reactivation were screened through the direct Strout method (SM) before BMT.…”

Congenital Trypanosoma cruzi Infection. Efficacy of Its Monitoring in an Urban Reference Health Center in a Non-Endemic Area of Argentina

“…Inclusion criteria for pregnant women in the congenital CHD protocol was serological reactivity for CHD in at least two serological tests, such as indirect immunofluorescence assay (IFA), enzyme-linked immunosorbent assay (ELISA), and indirect hemagglutination (IHA) standardized in our institute. [12][13][14][15] Babies born to CHD mothers met the inclusion criterion in the protocol. Children were excluded when they had received blood transfusions, or were born or had been in transit in endemic areas.…”

“…When two or three tests were performed simultaneously, the sensitivity ranges from 99.7% to 100% and the specificity from 97.4% to 97.9%. [12][13][14][15] Titers equal or higher than 0.200 of optical density at 490 nm for ELISA, and 1/32 for IHA and IFA were considered reactive for T. cruzi infection.…”

Long-term effects of a nationwide control program on the seropositivity for Trypanosoma cruzi infection in young men from Argentina.

“…Quality control procedures were based on the agreement of serum panel results sub- mitted for confirmation to INDIECH by all participating laboratories from 1981 to 1986. 24 The quality control program included: 1) internal quality control tests, in which positive and negative control sera were monitored on a daily basis, and 2) external quality control, consisting of proficiency tests with unknown positive and negative control sera provided by the national reference center, and confirmation of serum results submitted to the national reference center by the participating laboratories. These proficiency and confirmation tests were carried out annually before the mass serologic screening; probable sources of error were identified and implementation of corrective measures were introduced when necessary.…”

“…These proficiency and confirmation tests were carried out annually before the mass serologic screening; probable sources of error were identified and implementation of corrective measures were introduced when necessary. 24 In cooperation with the neighboring countries, the national reference center has been coordinating an international reference serum panel for the control of Chagas' disease serology since 1993.…”