RESUMO
We evaluated a commercially available immunochromatographic dipstick test to detect Trypanosoma cruzi infection in 366 human serum samples with known serological results from Argentina, Ecuador, Mexico, and Venezuela. One hundred forty-nine of 366 (40.7%) and 171/366 (46.7%) samples tested positive by dipstick and serology, respectively. Dipstick sensitivity was calculated to be 84.8% (range between countries, 77.5 to 95%), and specificity was 97.9% (95.9 to 100%).
Assuntos
Doença de Chagas/diagnóstico , Parasitologia/métodos , Soro/parasitologia , Trypanosoma cruzi/isolamento & purificação , Argentina , Doença de Chagas/parasitologia , Equador , Humanos , Imunoensaio/métodos , México , Sensibilidade e Especificidade , Fatores de Tempo , Trypanosoma cruzi/imunologia , VenezuelaRESUMO
BACKGROUND: The Ecuadorian National Blood System collects approximately 100 000 units of blood per year. Screening for infectious agents is conducted by 23 autonomous blood services using different methodologies and reagents. OBJECTIVES: To evaluate the performance of serology testing by laboratories of the Ecuadorian National Blood Bank System. STUDY DESIGN: Four proficiency panels were distributed between April 2003 and December 2004 containing samples that were characterized as either reactive or non-reactive for hepatitis B surface antigen (HBsAg), antibodies against hepatitis C virus (HCV), and antibodies against human immunodeficiency virus (HIV). Laboratories were classified according to the volume of blood units processed per year, as small (<5000), medium (5000-12000) and large (>12000). RESULTS: Large and medium blood services consistently obtained better results than small ones. All of the 37 anti-HIV antibody false negative results and all of the 20 HBsAg false negative results were reported by small laboratories. False negative results were associated with the use of rapid tests. Laboratories using rapid tests and certain lots of an enzyme-linked immunosorbent assay (ELISA) failed to detect HCV reactive sera in December 2004. CONCLUSION: The high number of incorrect results in most small blood services indicates serious weaknesses in blood screening that require urgent corrective action. The National Blood System has implemented on-site audits, training, technical assistance, and increased oversight. The long-term proposal is to centralize blood testing in two large blood centers. The results presented here underline the importance of strengthening the regulatory framework and oversight in Ecuador and highlight the role of external performance evaluation programs for blood safety improvement.