Comparison of the Diagnostic Performances of Five Different Tests in Diagnosing Visceral Leishmaniasis in an Endemic Region of Ethiopia.

The lack of accurate and feasible diagnostic tests poses a significant challenge to visceral leishmaniasis (VL) healthcare services in endemic areas. To date, various VL diagnostic tests have been or are being developed, and their diagnostic performances need to be assessed. In the present study, the diagnostic performances of rk39 RDT, the direct agglutination test (DAT), microscopy, loop-mediated isothermal amplification (LAMP), and miniature direct-on-blood polymerase chain reaction-nucleic acid lateral flow immunoassay (mini-dbPCR-NALFIA) were assessed using quantitative polymerase chain reaction (qPCR) as the reference test in an endemic region of Ethiopia. In this study, 235 suspected VL cases and 104 non-endemic healthy controls (NEHCs) were recruited. Among the suspected VL cases, 144 (61.28%) tested positive with qPCR. The sensitivities for rk39 RDT, DAT, microscopy, LAMP assay, and mini-dbPCR-NALFIA were 88.11%, 96.50%, 76.58%, 94.33%, and 95.80%, respectively. The specificities were 83.33%, 97.96%, 100%, 97.38%, and 98.92% for rk39 RDT, DAT, microscopy, LAMP assay, and mini-dbPCR-NALFIA, respectively. In conclusion, rk39 RDT and microscopy exhibited lower sensitivities, while DAT demonstrated excellent performance. LAMP and mini-dbPCR-NALFIA showed excellent performances with feasibility for implementation in remote endemic areas, although the latter requires further evaluation in such regions.

Longitudinal profile of antibody response to SARS-CoV-2 in patients with COVID-19 in a setting from Sub-Saharan Africa: A prospective longitudinal study.

BACKGROUND: Serological testing for SARS-CoV-2 plays an important role for epidemiological studies, in aiding the diagnosis of COVID-19, and assess vaccine responses. Little is known on dynamics of SARS-CoV-2 serology in African settings. Here, we aimed to characterize the longitudinal antibody response profile to SARS-CoV-2 in Ethiopia. METHODS: In this prospective study, a total of 102 PCR-confirmed COVID-19 patients were enrolled. We obtained 802 plasma samples collected serially. SARS-CoV-2 antibodies were determined using four lateral flow immune-assays (LFIAs), and an electrochemiluminescent immunoassay. We determined longitudinal antibody response to SARS-CoV-2 as well as seroconversion dynamics. RESULTS: Serological positivity rate ranged between 12%-91%, depending on timing after symptom onset. There was no difference in positivity rate between severe and non-severe COVID-19 cases. The specificity ranged between 90%-97%. Agreement between different assays ranged between 84%-92%. The estimated positive predictive value (PPV) for IgM or IgG in a scenario with seroprevalence at 5% varies from 33% to 58%. Nonetheless, when the population seroprevalence increases to 25% and 50%, there is a corresponding increases in the estimated PPVs. The estimated negative-predictive value (NPV) in a low seroprevalence scenario (5%) is high (>99%). However, the estimated NPV in a high seroprevalence scenario (50%) for IgM or IgG is reduced significantly to 80% to 85%. Overall, 28/102 (27.5%) seroconverted by one or more assays tested, within a median time of 11 (IQR: 9-15) days post symptom onset. The median seroconversion time among symptomatic cases tended to be shorter when compared to asymptomatic patients [9 (IQR: 6-11) vs. 15 (IQR: 13-21) days; p = 0.002]. Overall, seroconversion reached 100% 5.5 weeks after the onset of symptoms. Notably, of the remaining 74 COVID-19 patients included in the cohort, 64 (62.8%) were positive for antibody at the time of enrollment, and 10 (9.8%) patients failed to mount a detectable antibody response by any of the assays tested during follow-up. CONCLUSIONS: Longitudinal assessment of antibody response in African COVID-19 patients revealed heterogeneous responses. This underscores the need for a comprehensive evaluation of seroassays before implementation. Factors associated with failure to seroconvert needs further research.

Effect of co-infection with intestinal parasites on COVID-19 severity: A prospective observational cohort study.

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection results in a spectrum of clinical presentations. Evidence from Africa indicates that significantly less COVID-19 patients suffer from serious symptoms than in the industrialized world. We and others previously postulated a partial explanation for this phenomenon, being a different, more activated immune system due to parasite infections. Here, we aimed to test this hypothesis by investigating a potential correlation of co-infection with parasites with COVID-19 severity in an endemic area in Africa. Methods: Ethiopian COVID-19 patients were enrolled and screened for intestinal parasites, between July 2020 and March 2021. The primary outcome was the proportion of patients with severe COVID-19. Ordinal logistic regression models were used to estimate the association between parasite infection, and COVID-19 severity. Models were adjusted for sex, age, residence, education level, occupation, body mass index, and comorbidities. Findings: 751 SARS-CoV-2 infected patients were enrolled, of whom 284 (37.8%) had intestinal parasitic infection. Only 27/255 (10.6%) severe COVID-19 patients were co-infected with intestinal parasites, while 257/496 (51.8%) non-severe COVID-19 patients were parasite positive (p<0.0001). Patients co-infected with parasites had lower odds of developing severe COVID-19, with an adjusted odds ratio (aOR) of 0.23 (95% CI 0.17-0.30; p<0.0001) for all parasites, aOR 0.37 ([95% CI 0.26-0.51]; p<0.0001) for protozoa, and aOR 0.26 ([95% CI 0.19-0.35]; p<0.0001) for helminths. When stratified by species, co-infection with Entamoeba spp., Hymenolepis nana, Schistosoma mansoni, and Trichuris trichiura implied lower probability of developing severe COVID-19. There were 11 deaths (1.5%), and all were among patients without parasites (p = 0.009). Interpretation: Parasite co-infection is associated with a reduced risk of severe COVID-19 in African patients. Parasite-driven immunomodulatory responses may mute hyper-inflammation associated with severe COVID-19. Funding: European and Developing Countries Clinical Trials Partnership (EDCTP) - European Union, and Joep Lange Institute (JLI), The Netherlands. Trial registration: Clinicaltrials.gov: NCT04473365.

Utility of the Loop-Mediated Isothermal Amplification Assay for the Diagnosis of Visceral Leishmaniasis from Blood Samples in Ethiopia.

Rapid and accurate diagnosis of visceral leishmaniasis (VL) is needed to initiate prompt treatment to reduce morbidity and mortality. Here, we evaluated the performance of loop-mediated isothermal amplification (LAMP) assay for the diagnosis of VL from blood in an endemic area in Ethiopia. LAMP was positive in 117/122 confirmed VL cases and negative in 149/152 controls, resulting in a sensitivity of 95.9% (95% CI: 90.69-98.66) and a specificity of 98.0% (95% CI: 94.34-99.59), respectively. The sensitivity of the LAMP assay was 95.0% (95% CI: 88.61-98.34) in HIV-negatives and 100% (95% CI: 85.18-100.0) in HIV-positives. Compared with microscopy, LAMP detected 82/87 (94.3%, 95% CI: 87.10-98.11) of the microscopy+ cases and was negative in 11/27 (40.7%, 95% CI: 22.39-61.20) of the microscopy- cases. Compared with the rK39 serology, LAMP detected 113/120 (94.2%, 95% CI: 88.35-97.62) of the rK39+ cases and was negative in 149/154 (96.8%, 95% CI: 92.59-98.94) of the rK39- cases. However, when compared with microscopy only, rK39 detected 83/87 (95.4%, 95% CI: 88.64-98.73) of the microscopy+ cases and negative in only 12/27 (44.4%, 95% CI: 25.48-64.67) of the microscopy- cases. There was an excellent agreement between rK39 and LAMP (Kappa = 0.91, 95% CI: 0.86-0.96). Furthermore, an algorithm using rK39 followed by LAMP would yield a sensitivity of 99.2% (95%CI: 95.52-99.89) and a specificity of 98.0% (95% CI: 94.34-99.59). The findings demonstrate that LAMP assay is an accurate and rapid molecular assay for VL diagnosis, including in HIV-1 coinfected patients, in an endemic setting.

The role of rk39 serologic test in the diagnosis of visceral leishmaniasis in a Tertiary Hospital, Northern Ethiopia.

BACKGROUND: The study is done in Ayder Referral Hospital in Northern Ethiopia. Ethiopia is one of the countries where visceral leishmaniasis (VL) is endemic. Diagnosis of VL in Ethiopia is primarily based on rK39 immunochromatographic (rk39-ICT) strip. This test has been shown to have variable sensitivity and specificity in different countries. Hence the objective of the study is to determine the sensitivity and specificity of rk39-ICT in the diagnosis of VL in our set up. The study participants were VL suspected patients admitted to the hospital. A cross sectional study design was used. The study was conducted from January 14, 2013 to June 26, 2015. The rK39-ICT strip used was the InBios brand. Ethical clearance was obtained from the IRB of the college and written consent was obtained from the individual patients. RESULTS: A total of 62 VL suspects were involved in the study. The mean age was 26.3 years (SD = 6.94 years) with a median age of 25.5 years. Sixty-one (98.4%) of the patients was males. The rK39-ICT was positive in 50 (80.6%) of the patients. Splenic aspiration was positive in 44 (71%) of the patients. In 37 (59.7%) of the patients both rK39 and splenic aspiration were positive. Thirteen (21%) of the patients had positive rK39 but negative splenic aspiration. Five (8.1%) of the patients had both negative rK39 and splenic aspiration however seven (11.3%) of the patients had rk39 negative but splenic aspiration positive. The sensitivity, specificity, positive predictive value and the negative predictive value of rK39-ICT, taking splenic aspiration as a gold standard test, is 84.1% (95% CI 69.9-93.4%), 27.8% (95% CI 9.7-53.5%), 74.0% (95% CI 60-85.4%) and 41.7% (95% CI 15.2-72.3%) respectively. CONCLUSION: Sensitivity of rK39-ICT is low and its specificity is poor in our set up. Significant number of patients with confirmed VL did not have travel history to endemic areas. We recommend that the rK39-ICT needs improvement for clinical use in our set up and case definition for visceral leishmaniasis in Ethiopia needs to be revisited.