ABSTRACT Background: The screening of Trypanosoma cruzi-infected blood donors using two serological techniques frequently leads to conflicting results. This fact prompted us to evaluate the diagnostic performance of four “in-house” immunodiagnostic tests and two commercially available enzyme-linked immunosorbent assays (ELISAs). Material and Methods: One hundred and seventy-nine blood donors, whose screening for Chagas disease was doubtful, underwent three in-house ELISAs, one in-house immunoblotting test (TESA-blot), and two commercial ELISAs (bioMérieux and Wiener) in an attempt to define the presence or absence of infection. Simultaneously, 29 donors with previous positive results from three conventional serological tests and 30 donors with constant negative results were evaluated. Results: The ELISA-Wiener showed the highest rate in sensitivity (98.92%) and the ELISA-bioMérieux, the highest specificity (99.45%), followed by the TESA-blot, which showed superior performance, with lower false-negative (2.18%) and false-positive (1.12%) rates. In series, the combination composed of the TESA-blot and ELISA-bioMérieux showed slightly superior performance, with trifunctional protein deficiency (TFP) = 0.01%. Conclusion: Our study confirms the high sensitivity and specificity of commercial kits. To confirm the presence or absence of T. cruzi infection, the combination of TESA-blot and ELISA-bioMérieux may be suggested as the best alternative. Individually, the TESA-blot performed the closest to the gold standard; however, it is not commercially available.

Complement receptor 1 (CR1) gene polymorphisms that are associated with Knops blood group antigens may influence the binding of Plasmodium parasites to erythrocytes, thereby affecting susceptibility to malaria. The aim of this study was to evaluate the genotype and allele and haplotype frequencies of single-nucleotide polymorphisms (SNPs) of Knops blood group antigens and examine their association with susceptibility to malaria in an endemic area of Brazil. One hundred and twenty-six individuals from the Brazilian Amazon were studied. The CR1-genomic fragment was amplified by PCR and six SNPs and haplotypes were identified after DNA sequence analysis. Allele and haplotype frequencies revealed that the Kn b allele and H8 haplotype were possibly associated with susceptibility to Plasmodium falciparum. The odds ratios were reasonably high, suggesting a potentially important association between two Knops blood antigens (Kn b and KAM+) that confer susceptibility to P. falciparum in individuals from the Brazilian Amazon.

INTRODUÇÃO: A doação de sangue causa redução substancial na quantidade de ferro do organismo (cada unidade de sangue retirada [425 a 475 ml] contém 200 a 250 mg de ferro) com conseqüente mobilização do ferro de depósito. Recentes estudos têm demonstrado que as reservas de ferro do organismo são pequenas, e sua deficiência é mais freqüente nos doadores de sangue que nos indivíduos não-doadores de sangue. OBJETIVO: Avaliar a freqüência da deficiência de ferro em doadores de sangue do Hemocentro da Santa Casa de São Paulo segundo o sexo, o tipo de doador e a freqüência de doações realizadas nos últimos 12 meses. LOCAL: Hemocentro da Santa Casa de São Paulo. PARTICIPANTES: No período de 20 de setembro a 5 de outubro de 1999 foram estudados 300 doadores de sangue. TESTES DIAGNÓSTICOS: Utilizamos a determinação das dosagens do ferro sérico, da capacidade total de ligação do ferro, do índice de saturação da transferrina, da ferritina sérica e dos índices eritrocitários. RESULTADOS: A freqüência de doadores de sangue que apresentavam deficiência de ferro observada foi de 11, 0 % (33/300), sendo 5, 5% (13/237)nos doadores do sexo masculino e de 31, 7% (20/63) nos doadores do sexo feminino. Para as mulheres, 18, 5% delas já apresentavam deficiência de ferro à primeira doação de sangue, e para as doadoras freqüentes foi 41, 5%. Entre os homens, nenhum doador apresentava deficiência de ferro à primeira doação de sangue e, para os doadores freqüentes, a deficiência de ferro foi de 7, 6%. A freqüência observada foi maior para os doadores com três ou mais doações nos últimos 12 meses (P < 0,05) e para as doadoras com duas ou mais doações nos últimos 12 meses (P < 0,05). CONCLUSÕES: A doação de sangue constitui-se numa causa importante de deficiência de ferro em doadores de sangue, particularmente nos doadores freqüentes do sexo feminino. A elevada freqüência de doadores de sangue com deficiência de ferro observada nesse estudo sugere a necessidade de uma triagem laboratorial mais acurada, uma vez que a determinação isolada da hemoglobina ou do hematócrito não é suficiente para detectar e excluir os doadores com deficiência de ferro ainda sem anemia.

CONTEXT: Blood donation results in a substantial loss of iron (200 to 250 mg) at each bleeding procedure (425 to 475 ml) and subsequent mobilization of iron from body stores. Recent reports have shown that body iron reserves generally are small and iron depletion is more frequent in blood donors than in non-donors. OBJECTIVE: The aim of this study was to evaluate the frequency of iron deficiency in blood donors and to establish the frequency of iron deficiency in blood donors according to sex, whether they were first-time or multi-time donors, and the frequency of donations per year. DESIGN: From September 20 to October 5, 1999, three hundred blood donors from Santa Casa Hemocenter of São Paulo were studied. DIAGNOSTIC TESTS: Using a combination of biochemical measurements of iron status: serum iron, total iron-binding capacity, transferrin saturation index, serum ferritin and the erythrocyte indices. RESULTS: The frequency of iron deficiency in blood donors was 11.0%, of whom 5.5% (13/237) were male and 31.7% (20/63) female donors. The frequency of iron deficiency was higher in multi-time blood donors than in first-time blood donors, for male blood donors (7.6% versus 0.0%, P < 0.05) and female ones (41.5% versus 18.5%, P < 0.05). The frequency of iron deficiency found was higher among the male blood donors with three or more donations per year (P < 0.05) and among the female blood donors with two or more donations per year (P < 0.05). CONCLUSIONS: We conclude that blood donation is a very important factor for iron deficiency in blood donors, particularly in multi-time donors and especially in female donors. The high frequency of blood donors with iron deficiency found in this study suggests a need for a more accurate laboratory trial, as hemoglobin or hematocrit measurement alone is not sufficient for detecting and excluding blood donors with iron deficiency without anemia.