Hematological malignancies as disorders negatively impacting specificities of the direct agglutination and rapid rK39 strip tests as reference diagnostics for visceral leishmanisis

Abstract

Introduction: During several years of work in Sudan, we occasionally had been confronted with patients who presented clinical features highly suggestive of visceral leishmaniasis (VL) however direct agglutination test (DAT) readings that were either at the high negative or low positive titre range. Inquiries on the fate of those particular patients revealed mortality, undetermined diagnosis or that in some of them leukemia was finally diagnosed.Gap statement: Investigate as to what extent hematological malignancies (HMs) interfere with VL diagnosis.Aim: Evaluate specificity of DAT version newly developed in this study wherein sodium dodecyle sulphate (SDS) was incorporated as a test sample denaturant in comparison with a standard reference wherein β-mercaptoethanol (β-ME) was used in test execution.Methodology: Seventy plasma samples from patients with HMs were collected and tested in a primary DAT version (P-DAT). The results obtained were compared with those of the rK39 strip test as VL reference diagnostic. HM samples revealing titres higher than the start dilution (1:100) in P-DAT were further tested in a β-ME- and urea- modified DAT versions. The specificity of the newly developed SDS-DAT was assessed against that of β-ME-DAT and rK39 strip tests as current reference diagnostics for VL.Results: Seven out of 70 patients with HMs scored positive outcomes (titre >1:3200) in P-DAT and 4 in the reference rK39 strip test. Of the 7 that tested positive in P-DAT or 4 in the reference rK39, none reacted at titre > 1:100 in the SDS-DAT. Significant reduction in non-specific agglutination reactions was achieved as a result in respect to the HM plasma samples (P. value < 0.05).Conclusion: To establish desired specificity for VL diagnosis in respect to HMs and subsequently minimize or avoid serious side effects due to unjustified anti-leishmanials prescription the combined application of the SDS-DAT here described and an improved version of the rK39 for confirmation is recommended. Key words: Visceral leishmaniasis; diagnosis; hematological malignancies; DAT; rK39; anti-leishmanials; SDS.

Validation of an improved reference freeze-dried direct agglutination test for the detection of leishmaniasis in the canine reservoir

“…However because of the associated health hazards and inconvenience in use, reducing agents with minimal or no toxicity such as urea was introduced with success. In this study we also have considered the possibility of introducing a third reducing agent namely the SDS emerging from the highly encouraging results recently observed with human plasma from patients diagnosed with hematological malignancies (13). As shown in Table 1, all three reducing agents performed satisfactorily in lowering of non-speci c agglutination reactions in the CVL negatives while showing increase or maintaining levels in those of the speci c noticeably enhancing therefore speci city of all four DAT versions.…”

“…or urea (0.3% wt/vol) were used as reducing agents in the FCS or gelatin/saline diluent as described in details earlier (7). Based on recent observations, supplementation of sodium dodecyle sulphate (SDS) (0.045 mM) in a gelatin diluent containing NaCL (0.15 M), CaCl2 (0.02 M ), KCl (0.05 M) and NaHCO3(0.05M) proved to be highly e cient for the elimination of non-speci c agglutination and therefore included in this study as a third reducing agent (13).…”