The application of latent class analysis for diagnostic test validation of chronic Trypanosoma cruzi infection in blood donors

The main strategy to prevent transfusion-associated Chagas' disease is the identification of T. Cruzi-infected blood donors by serological screening tests, however there is no perfect serological gold standard. We evaluated an enzyme immunoassay (EIA), an indirect hemaglutination (IHA), and an indirect immunofluorescence (IIF) test for detecting T. Cruzi antibodies in Brazilian blood donors. The results were submitted to latent class analysis, and a radioimmunopreciptation (RIPA) test was performed on repeatedly positive samples. Among 1951 donors, 11 (0.56%) were positive by EIA, 6 (0.31%) by IHA and 16 (0.82%) by IIF. Six samples were positive with all tests, while 4 reacted with EIA and IIF. The RIPA was positive in 6 (75.0%), 7 (66.6%), and 4 (54.0%) samples reacting by the EIA, IHA and IIF tests, respectively. The latent class model detected a high sensitivity rate (100%) for the EIA and IIF, and a specificity rate of 99.95% and 99.69% for the EIA and IIF tests, respectively. The probability of being case according to the model was 99.92% when both EIA and IIF were positive, and 100% for the association of EIA, IIF, and IHA

Avaliação laboratorial da deficiência de ferro em doadoras de sangue Laboratory analysis of iron deficiency in female blood donors

O objetivo deste estudo foi avaliar a freqüência da deficiência de ferro em doadoras de sangue do Hemocentro da Santa Casa de São Paulo segundo o tipo de doador, o número total de doações anteriores e a freqüência de doações realizadas nos últimos 12 meses. No período de 05 a 20 de outubro de 2004 foram estudadas 100 doadoras de sangue utilizando-se a determinação da ferritina sérica e dos índices eritrocitários. A freqüência de doadoras de sangue que apresentavam deficiência de ferro foi de 16,0 %. Para as doadoras de primeira vez, 10,5% delas já apresentavam deficiência de ferro à primeira doação de sangue e, para aquelas que não eram de primeira vez, essa freqüência foi de 17,7% (pThe aim of this study was to evaluate the frequency of iron deficiency in blood donors at the Santa Casa Blood Bank and to establish the frequency of iron deficient blood donors according to first-time and multiple donors, the total number of lifetime donations and the frequency of donations per year. Between 5th and 20th October 2004, one hundred blood donors were studied using the biochemical measurement of serum ferritin and red blood cell indices. The frequency of iron deficiency in blood donors was 16.0%. The frequency of iron deficiency was higher in non-first-time than in first-time female blood donors (10.5% versus 17.7%; p<0.05). The frequency of iron deficiency was higher in the multiple blood donors and this difference was statistically significative in female blood donors after more than four donations (p<0.05) and among female blood donors with two or more donations per year (p<0.05). We conclude that blood donation is a very important factor of iron deficiency in female blood donors, particularly in multiple donors. The high frequency of blood donors with iron deficiency found in this study suggests the necessity for more accurate laboratory screening, as the hemoglobin or hematocrit measurements alone are insufficient to detect and exclude blood donors with iron deficiency without anemia