Diagnostic accuracy of direct agglutination test, rK39 ELISA and six rapid diagnostic tests among visceral leishmaniasis patients with and without HIV coinfection in Ethiopia.

Diagnosis of a first-time visceral leishmaniasis (VL) infection in Ethiopia is established by use of a rapid diagnostic test (RDT) detecting antibodies against rK39, direct agglutination test (DAT) and microscopy according to the national algorithm. The performance of individual tests and algorithm is variable and depends on several factors, one being HIV status. Limited data are available on the performance of tests in VL-HIV coinfected patients. Assessment of the performance of DAT (ITM-A), rK39 ELISA (Serion) and six RDT (Onsite Leishmania Ab CTK, Antigen ICT Xinjier, IT Leish Biorad, Kalazar Detect Inbios, rK39 IgG1 Coris, rk28 IgG1 Coris) for the diagnosis of VL was done on a panel of 91 stored serum and plasma samples of 'first-episode' suspected VL patients, with HIV coinfection (n = 51) and without (n = 40). A combined reference standard was used: either positive microscopy on tissue aspirates, or in case of negative microscopy, positive PCR results on the aspirate slide. Additionally, endemic healthy controls (n = 20), non-endemic controls (n = 10) and patients with confirmed malaria infection (n = 10) were tested for specificity evaluation. Sensitivities ranged from 69.2% for DAT (applied cut-off ≥ 1/3200) to 92.2% for the Onsite RDT, whereas specificities ranged from 20.0% for Kalazar Antigen ICT to 100% for IT Leish and rK39 IgG1. Sensitivities from all assays decreased upon stratification according to HIV status but was only significantly different for rK39 Serion ELISA (p-value 0.0084) and the Onsite RDT (p-value 0.0159). In conclusion, performance of commercially available assays for VL on samples from Northern-Ethiopian patients varied widely with a substantial decrease in sensitivity in the VL-HIV coinfected group. Clear guidelines on minimal performance criteria of individual tests and algorithms are needed, as well as which reference standard should be used to determine the performance.

Detection of Immunoglobulin G1 Against rK39 Improves Monitoring of Treatment Outcomes in Visceral Leishmaniasis.

BACKGROUND: Visceral leishmaniasis (VL), caused by the Leishmania donovani complex, is a fatal, neglected tropical disease that is targeted for elimination in India, Nepal, and Bangladesh. Improved diagnostic tests are required for early case detection and for monitoring the outcomes of treatments. Previous investigations using Leishmania lysate antigen demonstrated that the immunoglobulin (Ig) G1 response is a potential indicator of a patient's clinical status after chemotherapy. METHODS: IgG1 or IgG enzyme-linked immunosorbent assays (ELISAs) with rK39 or lysate antigens and novel IgG1 rK39 rapid diagnostic tests (RDTs) were assessed with Indian VL serum samples from the following clinical groups: paired pre- and postchemotherapy (deemed cured); relapsed; other infectious diseases; and endemic, healthy controls. RESULTS: With paired pre- and post-treatment samples (n = 37 pairs), ELISAs with rK39- and IgG1-specific conjugates gave a far more discriminative decrease in post-treatment antibody responses when compared to IgG (P < .0001). Novel IgG1 rK39 RDTs provided strong evidence for decreased IgG1 responses in patients who had successful treatment (P < .0001). Furthermore, both IgG1 rK39 RDTs (n = 38) and ELISAs showed a highly significant difference in test outcomes between cured patients and those who relapsed (n = 23; P < .0001). RDTs were more sensitive than corresponding ELISAs. CONCLUSIONS: We present strong evidence for the use of IgG1 in monitoring treatment outcomes in VL, and the first use of an IgG1-based RDT using the rK39 antigen for the discrimination of post-treatment cure versus relapse in VL. Such an RDT may have a significant role in monitoring patients and in targeted control and elimination of this devastating disease.

Severity of Chagasic Cardiomyopathy Is Associated With Response to a Novel Rapid Diagnostic Test for Trypanosoma cruzi TcII/V/VI.

Background: Trypanosoma cruzi causes Chagas disease in the Americas. The outcome of infection ranges from lifelong asymptomatic status to severe disease. Relationship between T. cruzi lineage (TcI-TcVI) infection history and prognosis is not understood. We previously described peptide-based lineage-specific enzyme-linked immunosorbent assay (ELISA) with trypomastigote small surface antigen (TSSA). Methods: A novel rapid diagnostic test (RDT; Chagas Sero K-SeT) that incorporates a peptide that corresponds to the TSSA II/V/VI common epitope was developed and validated by comparison with ELISA. Patients from Bolivia and Peru, including individuals with varying cardiac pathology, and matched mothers and neonates, were then tested using Chagas Sero K-SeT. Results: Chagas Sero K-SeT and ELISA results, with a Bolivian subset of cardiac patients, mothers, and neonates, were in accord. In adult chronic infections (n = 121), comparison of severity class A (no evidence of Chagas cardiomyopathy) with class B (electrocardiogram suggestive of Chagas cardiomyopathy) and class C/D (decreased left ventricular ejection fraction; moderate/severe Chagas cardiomyopathy) revealed a statistically significant increase in Chagas Sero K-SeT reactivity with increasing severity (χ2 for trend, 7.39; P = .007). In Peru, Chagas Sero K-SeT detected the sporadic TcII/V/VI infections. Conclusions: We developed a low cost RDT that can replace ELISA for identification of TSSA II/V/VI immunoglobulin G. Most importantly, we show that response to this RDT is associated with severity of Chagas cardiomyopathy and thus may have prognostic value. Repeated challenge with T. cruzi infection may both exacerbate disease progression and boost the immune response to the TSSApep-II/V/VI epitope.