| Autor: |
Harith AE; School of Pharmacy, Ahfad University for Women, Omdurman, Sudan., Awad Y; School of Pharmacy, Ahfad University for Women, Omdurman, Sudan., Mahamoud A; School of Pharmacy, Ahfad University for Women, Omdurman, Sudan., Abass E; Department of Clinical Laboratory Science, College of Applied Medical Sciences, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia., Mansour D; School of Health Sciences, Ahfad University for Women, Omdurman, Sudan., Moura de Melo C; Program in Health and Environment, University of Tiradentes, Aracaju, Brazil., Madi RR; Program in Health and Environment, University of Tiradentes, Aracaju, Brazil., Semiao-Santos SJ; Department of Medicine and Nursing, University of Tiradentes, Aracaju, Brazil., Osman HA; School of Pharmacy, Ahfad University for Women, Omdurman, Sudan. |
| Abstrakt: |
Currently, a significantly lower temperature (35°C) than initially established (56°C) is indicated as the maximum temperature storage for the commercial reference visceral leishmaniasis (VL) freeze-dried direct agglutination test (FD-DAT). Despite an approximately 50% loss in the number of promastigotes in an FD-DAT batch that expired 7 years earlier, the promastigotes maintained a similar morphology to the equivalent valid batch implying most likely that auto-agglutination, rather than aging, is the main reason for expiry. The substitution of normal saline which was initially recommended for reconstitution, by citrate-saline/formaldehyde (CSF) as an anti-clumping/preservative agent resulted in restoration of validity comparable with that of the freeze-dried original or the liquid direct agglutination test (LQ-DAT) version (Friedman ANOVA test = 1.0588; P = 0.5890). Following a similar reconstitution procedure as for the 7-year expired antigen, using significantly lower promastigote concentration (1.4 × 10 7 /mL) than in the non-expired (9.0 × 10 7 /mL), good reliability for VL detection and stability at 4°C (> 12 months) were achieved. In comparison with the original version using normal saline ($32.0/vial), the cost-effectiveness of the FD-DAT was appreciably improved by the CSF incorporation and lowering of promastigote concentration per unit suspension medium ($12.8/vial). With diagnostic reliability comparable with the full-out titration used, FD-DAT procedure based on single sample dilution at the VL cutoff (1:3,200) permitted the use of significantly smaller antigen volumes (0.1 mL vs. > 1.5 mL), therefore contributing to a further reduction in the application cost. The successful replacement of β-mercaptoethanol (β-ME) by urea ( T = 21.00; P = 0.0868) provided the required safety for the test procedure similar to the widely applied LQ-DAT. |
