Low quality of routine microscopy for malaria at different levels of the health system in Dar es Salaam

ABSTRACT: BACKGROUND: Laboratory capacity to confirm malaria cases in Tanzania is low and presumptive treatment of malaria is being practiced widely. In malaria endemic areas WHO now recommends systematic laboratory testing when suspecting malaria. Currently, the use of Rapid Diagnostic Tests (RDTs) is recommended for the diagnosis of malaria in lower level peripheral facilities, but not in health centres and hospitals. In this study, the following parameters were evaluated: (1) the quality of routine microscopy, and (2) the effects of RDT implementation on the positivity rate of malaria test results at three levels of the health system in Dar es Salaam, Tanzania. METHODS: During a baseline cross-sectional survey, routine blood slides were randomly picked from 12 urban public health facilities in Dar es Salaam, Tanzania. Sensitivity and specificity of routine slides were assessed against expert microscopy. In March 2007, following training of health workers, RDTs were introduced in nine public health facilities (three hospitals, three health centres and three dispensaries) in a near-to-programmatic way, while three control health facilities continued using microscopy. The monthly malaria positivity rates (PR) recorded in health statistics registers were collected before (routine microscopy) and after (routine RDTs) the intervention in all facilities. RESULTS: At baseline, 53% of blood slides were reported as positive by the routine laboratories, whereas only 2% were positive by expert microscopy. Sensitivity of routine microscopy was 71.4% and specificity was 47.3%. Positive and negative predictive values were 2.8% and 98.7%, respectively. Median parasitaemia was only three parasites per 200 white blood cells (WBC) by routine microscopy compared to 1226 parasites per 200 WBC by expert microscopy. Before RDT implementation, the mean test positivity rates using routine microscopy were 43% in hospitals, 62% in health centres and 58% in dispensaries. After RDT implementation, mean positivity rates using routine RDTs were 6%, 7% and 8%, respectively. The sensitivity and specificity of RDTs using expert microscopy as reference were 97.0% and 96.8%. The positivity rate of routine microscopy remained the same in the three control facilities: 71% before versus 72% after. Two cross-sectional health facility surveys confirmed that the parasite rate in febrile patients was low in Dar es Salaam during both the rainy season (13.6%) and the dry season (3.3%). CONCLUSIONS: The quality of routine microscopy was poor in all health facilities, regardless of their level. Over-diagnosis was massive, with many false positive results reported as very low parasitaemia (1 to 5 parasites per 200 WBC). RDTs should replace microscopy as first-line diagnostic tool for malaria in all settings, especially in hospitals where the potential for saving lives is greates

Cost Savings with Rapid Diagnostic Tests for Malaria in Low-Transmission Areas: Evidence from Dar es Salaam, Tanzania

Rapid diagnostic tests (RDTs) for malaria may help rationalize antimalarial drug use. However, the economic effects of these tests may vary. Data on costs were collected from 259 patients in 6 health facilities by using exit and in-charge interviews and record reviews during a trial of RDT rollout in Dar es Salaam, Tanzania. The RDTs decreased patient expenditure on drugs (savings = U.S. $0.36; P = 0.002) and provider drug costs (savings = U.S.$0.43; P = 0.034) compared with control facilities. However, RDT introduction did not significantly reduce patients' overall expenditures (U.S. $1.02, 95$0.76–$1.36 versus U.S.$1.33 95% CI = $0.99–$1.77) and may increase total provider costs (U.S. $3.63, 95$3.40–$3.89 versus U.S.$2.32, 95% CI = $1.99–$2.69) compared with control facilities. Clinician's compliance with test results was higher with RDTs than with routine microscopy (95% versus 82%; P = 0.002). The RDTs reduced drug costs in this setting but did not offset the cost of the tests, although they also resulted in non-monetary benefits, including improved management of patients and increased compliance with test results

Erratum for Williams et al., "Investigation of the Plasma Virome from Cases of Unexplained Febrile Illness in Tanzania from 2013 to 2014: a Comparative Analysis between Unbiased and VirCapSeq-VERT High-Throughput Sequencing Approaches"

High-throughput sequencing can provide insights into epidemiology and medicine through comprehensive surveys of viral genetic sequences in environmental and clinical samples. Here, we characterize the plasma virome of Tanzanian patients with unexplained febrile illness by using two high-throughput sequencing methods: unbiased sequencing and VirCapSeq-VERT (a positive selection system). Sequences from dengue virus 2, West Nile virus, human immunodeficiency virus type 1, human pegivirus, and Epstein-Barr virus were identified in plasma. Both sequencing strategies recovered nearly complete genomes in samples containing multiple viruses. Whereas VirCapSeq-VERT had better sensitivity, unbiased sequencing provided better coverage of genome termini. Together, these data demonstrate the utility of high-throughput sequencing strategies in outbreak investigations. <b>IMPORTANCE</b> Characterization of the viruses found in the blood of febrile patients provides information pertinent to public health and diagnostic medicine. PCR and culture have historically played an important role in clinical microbiology; however, these methods require a targeted approach and may lack the capacity to identify novel or mixed viral infections. High-throughput sequencing can overcome these constraints. As the cost of running multiple samples continues to decrease, the implementation of high-throughput sequencing for diagnostic purposes is becoming more feasible. Here we present a comparative analysis of findings from an investigation of unexplained febrile illness using two strategies: unbiased high-throughput sequencing and VirCapSeq-VERT, a positive selection high-throughput sequencing system

Changes in SARS-CoV-2 Spike versus Nucleoprotein Antibody Responses Impact the Estimates of Infections in Population-Based Seroprevalence Studies

SARS-CoV-2-specific antibody responses to the Spike (S) protein monomer, S protein native trimeric form or the nucleocapsid (N) proteins were evaluated in cohorts of individuals with acute infection (n=93) and in individuals enrolled in a post-infection seroprevalence population study (n=578) in Switzerland. Commercial assays specific for the S1 monomer, for the N protein and a newly developed Luminex assay using the S protein trimer were found to be equally sensitive in antibody detection in the acute infection phase samples. Interestingly, as compared to anti-S antibody responses, those against the N protein appear to wane in the post-infection cohort. Seroprevalence in a 'positive patient contacts' group (n=177) was underestimated by N protein assays by 10.9 to 32.2% and the 'random selected' general population group (n=311) was reduced up to 45% reduction relative to S protein assays. The overall reduction in seroprevalence targeting only anti-N antibodies for the total cohort ranged from 9.4 to 31%. Of note, the use of the S protein in its native trimer form was significantly more sensitive as compared to monomeric S proteins. These results indicate that the assessment of anti-S IgG antibody responses against the native trimeric S protein should be implemented to estimate SARS-CoV-2 infections in population-based seroprevalence studies.IMPORTANCE In the present study, we have determined SARS-CoV-2-specific antibody responses in sera of acute and post-infection phase subjects. Our results indicate that antibody responses against viral S and N proteins were equally sensitive in the acute phase of infection but that responses against N appear to wane in the post-infection phase while those against S protein persist over time. The most sensitive serological assay in both acute and post-infection phases used the native S protein trimer as binding antigen that has significantly greater conformational epitopes for antibody binding compared to the S1 monomer protein used in other assays. We believe that these results are extremely important in order to generate correct estimates of SARS-CoV-2 infections in the general population. Furthermore, the assessment of antibody responses against the trimeric S protein will be critical to evaluate the durability of the antibody response and for the characterization of a vaccine-induced antibody response

Migrants from Sub-Saharan Africa in the Swiss HIV Cohort Study: access to antiretroviral therapy, disease progression and survival

OBJECTIVE: To examine the proportion of migrants from Sub-Saharan Africa entering the Swiss HIV Cohort Study (SHCS) and to compare these participants with participants from Northwestern Europe for access to antiretroviral therapy, progression to AIDS and survival. DESIGN: Prospective national cohort study of HIV-1-infected adults from seven HIV centres in Switzerland. METHODS: Trends in the proportion of participants from Sub-Saharan Africa were followed in 11 872 HIV-infected adults entering the SHCS from 1984 to 2001. Survival methods were used to compare uptake of antiretroviral therapy, survival and progression to AIDS in the 2684 participants from Sub-Saharan Africa and Northwest Europe enrolled from 1997-2001. RESULTS: There was a steady increase in the proportion of Sub-Saharan African participants over time, reaching 11.9% in 1997-2001. These participants were more likely to be younger, female, to have been infected by heterosexual intercourse and had lower CD4 cell counts at presentation. There were no differences between Sub-Saharan Africans and Northwest Europeans in uptake of triple antiretroviral therapy, progression to AIDS or survival up to 48 months after starting treatment. Tuberculosis was the most frequent AIDS-defining event in Sub-Saharan African patients. CONCLUSIONS: There is no evidence that access to potent antiretroviral therapy is influenced by geographic origin of participants. The prognosis of Sub-Saharan African patients on triple therapy is equivalent to that of Northwest European patients. Future research should address wider issues about access to specialist health services for HIV-infected people from Sub-Saharan Africa

A high-throughput cell- and virus-free assay shows reduced neutralization of SARS-CoV-2 variants by COVID-19 convalescent plasma

The detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific antibodies in the serum of an individual indicates previous infection or vaccination. However, it provides limited insight into the protective nature of this immune response. Neutralizing antibodies recognizing the viral spike protein are more revealing, yet their measurement traditionally requires virus- and cell-based systems that are costly, time-consuming, inflexible, and potentially biohazardous. Here, we present a cell-free quantitative neutralization assay based on the competitive inhibition of trimeric SARS-CoV-2 spike protein binding to the angiotensin-converting enzyme 2 (ACE2) receptor. This high-throughput method matches the performance of the gold standard live virus infection assay, as verified with a panel of 206 seropositive donors with varying degrees of infection severity and virus-specific immunoglobulin G titers, achieving 96.7% sensitivity and 100% specificity. Furthermore, it allows for the parallel assessment of neutralizing activities against multiple SARS-CoV-2 spike protein variants of concern. We used our assay to profile serum samples from 59 patients hospitalized with coronavirus disease 2019 (COVID-19). We found that although most sera had high activity against the 2019-nCoV parental spike protein and, to a lesser extent, the α (B.1.1.7) variant, only 58% of serum samples could efficiently neutralize a spike protein derivative containing mutations present in the β (B.1.351) variant. Thus, we have developed an assay that can evaluate effective neutralizing antibody responses to SARS-CoV-2 spike protein variants of concern after natural infection and that can be applied to characterize vaccine-induced antibody responses or to assess the potency of monoclonal antibodies

Target Product Profile for a Diagnostic Assay to Differentiate between Bacterial and Non-Bacterial Infections and Reduce Antimicrobial Overuse in Resource-Limited Settings: An Expert Consensus.

Acute fever is one of the most common presenting symptoms globally. In order to reduce the empiric use of antimicrobial drugs and improve outcomes, it is essential to improve diagnostic capabilities. In the absence of microbiology facilities in low-income settings, an assay to distinguish bacterial from non-bacterial causes would be a critical first step. To ensure that patient and market needs are met, the requirements of such a test should be specified in a target product profile (TPP). To identify minimal/optimal characteristics for a bacterial vs. non-bacterial fever test, experts from academia and international organizations with expertise in infectious diseases, diagnostic test development, laboratory medicine, global health, and health economics were convened. Proposed TPPs were reviewed by this working group, and consensus characteristics were defined. The working group defined non-severely ill, non-malaria infected children as the target population for the desired assay. To provide access to the most patients, the test should be deployable to community health centers and informal health settings, and staff should require 90% and >80% for sensitivity and specificity, respectively. Other key characteristics, to account for the challenging environment at which the test is targeted, included: i) time-to-result <10 min (but maximally <2 hrs); ii) storage conditions at 0-40°C, ≤90% non-condensing humidity with a minimal shelf life of 12 months; iii) operational conditions of 5-40°C, ≤90% non-condensing humidity; and iv) minimal sample collection needs (50-100μL, capillary blood). This expert approach to define assay requirements for a bacterial vs. non-bacterial assay should guide product development, and enable targeted and timely efforts by industry partners and academic institutions