A prospective study of urinary pneumococcal antigen detection in healthy Karen mothers with high rates of pneumococcal nasopharyngeal carriage

We nested an evaluation of the BinaxNOW S. pneumoniae test within a longitudinal mother-infant pneumococcal carriage study in Karen refugees on the Thailand-Myanmar border. Paired urine and nasopharyngeal swab specimens were collected from 98 asymptomatic women at a routine study follow-up visit. The urine specimens were analyzed with the BinaxNOW test and the nasopharyngeal swabs were semi-quantitatively cultured to identify pneumococcal colonization.24/98 (25%) women were colonized by S. pneumoniae but only three (3%) had a positive BinaxNOW urine test. The sensitivity of the BinaxNOW test for detection of pneumococcal colonization was 4.2% (95% CI: 0.1 - 21.1%) with a specificity of 97.3% (95% CI: 90.6 - 99.7%). Pneumococcal colonization was not associated with having a positive BinaxNOW test (odds ratio 1.6; 95% CI: 0.0 - 12.7; p = 0.7).Significant numbers of false positive results are unlikely to be encountered when using the BinaxNOW test to diagnose pneumococcal infection in adults from countries with moderate to high rates of pneumococcal colonization.Streptococcus pneumoniae is a leading bacterial cause of pneumonia globally [1]. Identifying pneumococcus as the etiological agent in pneumonia cases is difficult since unequivocal confirmation requires isolation of the organism from a sterile site. However, only ~10% of pneumonias are bacteremic and few sites are equipped to obtain lung tissue from pneumonia patients [2,3]. Detection of C-polysaccharide in urine (the BinaxNOW S. pneumoniae test (Inverness Medical, USA [now marketed by Alere Inc, USA])) has been demonstrated to be a useful rapid confirmatory test for pneumococcal infection in adults, with sensitivity of 74% and specificity of 94% in a recent systematic review [4]. Unfortunately the test has poor specificity in children due to detection of pneumococcal nasopharyngeal colonization: 22 - 67% of healthy children colonized with S. pneumoniae, from various countries, have been found to have a positiv