Evaluation of a rapid test for the diagnosis of pneumococcal pneumonia

We evaluated the usefulness of a rapid immunochromatographic pneumococcal urinary antigen test (UAT) for the diagnosis of pneumonia over a period of five years. The UAT was positive in 32 (2.3%) urine samples obtained from 1414 patients. In 46 of these 1414 patients results of UAT and/or sputum/pleural fluid culture and/or blood culture and/or procalcitonin levels were available and therefore the study was concentrated on these patients. A concordance between UAT positivity and the presence of Streptococcus pneumoniae in the sputum was observed in only 4 of 46 (8.7%) patients for which both urine and sputum samples were analyzed. A discordant result (UAT positive and absence of S. pneumoniae in sputum samples) was recorded in 8 of 46 (17.4 %) patients. UAT negative results with sputum culture positive for S. pneumoniae were recorded in 28.3% of patients. In 20 patients, UAT tested positive but sputum culture was not performed. A concordance between UAT positivity and the isolation of S. pneumoniae from blood was seen in 2 of 46 patients whereas a discordant result (UAT positive and blood culture negative) was seen in 12 (26.1%) patients. A concordance between the UAT and high levels (≥ 2 ng/ml) of procalcitonin was observed in 4 out of 46 patients, whereas a positive UAT result and a procalcitonin negative result were observed in 2 patients. In our experience the UAT allows the detection of the etiological agent of pneumonia, and also when sputum and/or blood cultures are negative for S. pneumoniae, when the clinical picture is suggestive of alveolar pneumonia.