In a previous study, the Chagas Stat-Pak test showed 100% sensitivity when assayed with sera collected in Honduras (5
). To confirm and extend these results, a larger number of serum samples (n
= 2,084) was analyzed with Chagas Stat-Pak and ELISA in three reference laboratories in Honduras (n
= 1,684), Nicaragua (n
= 200), and El Salvador (n
= 200) (Table ). From this total, 1,077 and 1,007 serum samples, respectively, were positive and negative by ELISA, while 1,074 and 1,010 samples, respectively, were positive and negative by Chagas Stat-Pak. This means that three sera with anti-T. cruzi
antibodies were recognized by ELISA but were not detected by the Chagas Stat-Pak. These three sera with discrepant results were tested also by IIF and by indirect hemagglutination, with positive results that were in accord with the ones obtained by the Wiener ELISA. The agreement between the two tests was 100% with sera from Nicaragua and 99.9% and 97.1% with sera from Honduras and El Salvador, respectively.
The rapid and accurate diagnosis of Chagas' disease is imperative in order to provide patients at the National Thorax Institute of Honduras with appropriate treatment and supportive therapy. Sera from 339 patients who consulted for the first time at the National Thorax Institute and were diagnosed as having cardiopathy were assayed using Chagas Stat-Pak (Table ). Ninety-seven patients were positive. The same result was confirmed for all samples with ELISA, with 100% agreement.
Chagas Stat-Pak was tested as a possible tool for use in emergencies in regions where Chagas' disease is endemic, where a donor should be evaluated quickly before his/her blood is delivered into a severely disabled patient. This situation is common in remote cities, where few facilities are available and where there are limited blood reserves. In such situations, fast methods should be used, or the patient may die. Using only Chagas Stat-Pak, the Red Cross Laboratory in Tegucigalpa (Honduras) tested 175 blood bags in emergencies that required surgical procedures during weekends or at night. Results were negative in 99.4% of the sera (n = 174); hence, blood was immediately transfused to the recipients. When Chagas Stat-Pak showed a positive result, the blood was refused, and blood from another negative donor was used instead. After recipients were transfused in emergencies with blood tested with Chagas Stat-Pak, the sera were tested with routine ELISA, which yielded the same results as the rapid test; i.e., 174 sera tested negative, and the single positive case detected by Chagas Stat-Pak was confirmed positive by ELISA (Table ).
The specificity of Chagas Stat-Pak was estimated in blood donor populations with both a high and low prevalence of Chagas' disease and compared with that of an ELISA using the same specimens (Table ). A total of 3,400 candidates for blood donation were screened by both tests in seven Honduran blood banks, with 156 positive (4.6%) by Chagas Stat-Pak. All of them were confirmed by ELISA, which is used routinely, with 100% agreement. There were no differences in the results among the seven blood banks that took part in this study for either test.