Dried blood spots for Streptococcus pneumoniae and Haemophilus influenzae detection and serotyping among children < 5 years old in rural Mozambique

Evaluation of Dried Blood and Cerebrospinal Fluid Filter Paper Spots for Storing and Transporting Clinical Material for the Molecular Diagnosis of Invasive Meningococcal Disease

To improve the storage and transport of clinical specimens for the diagnosis of Neisseria meningitidis (Nm) infections in resource-limited settings, we have evaluated the performance of dried blood spot (DBS) and dried cerebrospinal fluid spot (DCS) assays. DBS and DCS were prepared on filter paper from liquid specimens previously tested for Nm in the United Kingdom. Nm was detected and genogrouped by real-time PCR performed on crude genomic DNA extracted from the DBS (n = 226) and DCS (n = 226) specimens. Targeted whole-genome sequencing was performed on a subset of specimens, DBS (n = 4) and DCS (n = 6). The overall agreement between the analysis of liquid and dried specimens was (94.2%; 95% CI 90.8−96.7) for blood and (96.4%; 95% CI 93.5−98.0) for cerebrospinal fluid. Relative to liquid specimens as the reference, the DBS and DCS assays had sensitivities of (89.1%; 95% CI 82.7−93.8) and (94.2%; 95% CI 88.9−97.5), respectively, and both assays had specificities above 98%. A genogroup was identified by dried specimen analysis for 81.9% of the confirmed meningococcal infections. Near full-length Nm genome sequences (>86%) were obtained for all ten specimens tested which allowed determination of the sequence type, clonal complex, presence of antimicrobial resistance and other meningococcal genotyping. Dried blood and CSF filter spot assays offer a practical alternative to liquid specimens for the molecular and genomic characterisation of invasive meningococcal diseases in low-resource settings.

Systematic review and meta-analysis on the etiology of bacterial pneumonia in children in sub-Saharan Africa

Introduction

Before the introduction of vaccination to protect children from pneumonia, Streptococcus pneumoniae and Haemophilus influenzae type B (HiB) were the most frequent aetiological agents causing bacterial pneumonia in children under five years old. However, the etiology of childhood pneumonia appears to be changing and nonvaccine- type S. pneumoniae, non-typeable H. influenzae, and Staphylococcus aureus are becoming more relevant.

Objective

We conducted a systematic review aimed at identifying the common causes of bacterial pneumonia in children in sub-Saharan Africa.

Methods

We searched PubMed, Web of Science and African Index Medicus and included primary studies conducted since January 2010 that reported on the bacterial causes of pneumonia in children under five from sub-Saharan Africa. We extracted data items (about the study setting, pneumonia diagnosis, sampling, microbiological methods, and etiological agents) as well as study quality indicators.

Results

Streptococcus pneumoniae was the most common bacteria in blood cultures from children with pneumonia (8%, 95% CI: 4-14%), and H. influenzae was second (3%, 95% CI: 1-17%). Children’s nasopharynx commonly contained S. pneumoniae (66%), Moraxella catarrhalis (62%), and H. influenzae (44%).

Conclusion

S. pneumoniae and H. influenzae cause bacterial pneumonia in sub-Saharan African children. Our review also highlights the prevalence of potentially pathogenic bacteria in the nasopharynx of children under five and calls for more research into how nasopharyngeal colonization causes pneumonia.

Childhood Pneumonia Diagnostics in Sub-Saharan Africa: A Systematic Review

BACKGROUND

The prompt and accurate aetiological diagnosis of childhood pneumonia remains a challenge, especially in sub-Saharan Africa (SSA) because of limited resources for disease management.

OBJECTIVE

To review existing diagnostics for childhood pneumonia and potential modalities available to differentiate between bacterial and viral aetiologies in SSA.

METHODS

Online databases were searched for relevant articles published between January 2010 and December 2020 regarding childhood pneumonia diagnosis, conducted in SSA in children less than 18 years of age. The 2020 PRISMA checklist was utilized in appraising the selected studies and the QUADAS-2 tool was employed to assess the risk of bias in each of the studies selected.

RESULTS

A total of 1542 study titles and abstracts were screened following which 45 studies (39 on childhood pneumonia diagnostics and 6 on discriminating between bacterial and viral childhood pneumonia) were selected for review. Microbiological investigations (79.7%) constituted the most utilized index tests with blood-related specimen (32.8%) being the most utilized specimen. The most performed index diagnostic modality was polymerase chain reaction (PCR) (53.1%). The commonest reference gold standard technique was based on clinical diagnosis of the disease (46.2%). Only six studies in SSA attempted at using serum biomarkers, either singly or in combination to distinguish between aetiologies with use of combined biomarkers showing promise.

CONCLUSION

Microbiological investigations are the most employed diagnostic methods for childhood pneumonia in SSA. More studies are required to evaluate the potential use of serum biomarkers; either singly or in combination with the goal of discriminating bacterial and viral childhood pneumonia.

Diagnostic accuracy of dried blood spots for serology of vaccine-preventable diseases: a systematic review

INTRODUCTION

Venous serum and plasma are optimal specimens for serological testing but may be logistically infeasible. Dried blood spots (DBS) are a feasible alternative, provided results are adequately sensitive and specific. We aimed to assess the diagnostic accuracy of DBS to measure IgG and IgM antibodies for vaccine-preventable diseases and compare test validity of DBS with venous blood.

AREAS COVERED

In October 2020, we searched seven databases for peer-reviewed studies assessing the diagnostic accuracy of DBS specimens compared with serum in detecting antibodies to VPDs in humans. We extracted data and assessed risk of bias in all included studies. We calculated sensitivity and specificity with 95% confidence intervals for each index-reference test comparison. We narratively synthesized the identified evidence on diagnostic accuracy and blood collection and processing methods for DBS. Studies on measles and rubella IgG and IgM were the most frequently identified and reported generally high sensitivity and specificity.

EXPERT OPINION

Lack of standardization in collection, storage, and testing methods limited systematic comparison across studies. Our findings indicate a need for additional validation studies on the diagnostic accuracy of DBS to expand their use in serological surveillance. We recommend practical considerations to improve standardized reporting for DBS validation studies.