Comparison of Binax NOW urine antigen test and pneumococcal DNA assay using qPCR before and after nasopharyngeal swabbing in healthy Malawian children

E.A Lees,N French,L.A Mankhambo,Ed Carrol,M Guiver,D.K.K Ho

doi:10.1016/j.nmni.2015.08.001

Abstract

Diagnosis of invasive pneumococcal disease is challenging. We compared Binax NOW pneumococcal urinary antigen test with blood pneumococcal PCR in healthy Malawian children with and without pneumococcal carriage, and we found a high false-positive rate with Binax NOW. Blood pneumococcal PCR positivity was 66/88 (75%) compared to 5/27 (18%) when nasopharyngeal swabbing was performed first compared to after blood sampling for pneumococcal blood PCR. We speculate that nasopharyngeal swabbing may be causing a breach of mucosal integrity, leading to invasion into the bloodstream. These findings need to be confirmed with autolysin-based PCR assays.

Highlights

Invasive pneumococcal disease (IPD) is a major contributor to mortality in the developing world, especially in the context of HIV [1]
The Binax (Binax, Portland, ME, USA) Streptococcus pneumoniae antigen test is a rapid assay for the qualitative detection of S. pneumoniae antigen in the urine of patients with pneumonia and detects C-polysaccharide antigen
We aimed to compare the performance of Binax urine antigen test and a real-time blood PCR assay in healthy Malawian children with pneumococcal nasopharyngeal carriage before and after nasopharyngeal swabbing (NPS)

Summary

Introduction

Invasive pneumococcal disease (IPD) is a major contributor to mortality in the developing world, especially in the context of HIV [1]. The diagnosis of IPD is problematic, for pneumococcal pneumonia, because of a low rate of culturepositive patients, suggesting that the true disease burden is likely to be underestimated. Binax has been shown to have a sensitivity and specificity of 87% and 63%, respectively, for diagnosis of pneumococcal pneumonia, but pneumococcal antigen was detected in 43% of urine samples from healthy nasopharyngeal S. pneumoniae carriers [3]. Binax has been associated with false-positive findings, especially in children with high rates of nasopharyngeal pneumococcal colonization [4,5,6]

Objectives

Methods

Results