[Performance Evaluation of "BinaxNOW™ Streptococcus pneumoniae" Using Alere™ Reader].

Abstract

Streptococcus pneumoniae is one of the major bacterial pathogens of community-acquired pneumonia. Immunochromatographic assay tests are used to detect pneumococcal capsular antigen. In many cases, They can be read visually. The Alere™ reader (Reader), which was developed in October 2018 by Alere Medical Co., Ltd. (currently, Abbott Diagnostics Medical Co., Ltd.) for interpreting BinaxNOW™ Streptococcus pneumoniae test (BinaxNOW™), quickly displays the results of the immunochromatographic tests, objectively and accurately, as it was launched for the purpose of streamlining laboratory workflow. The performance of the reader was evaluated by using urine samples from 100 patients, who were ordered pneumococcal urine antigen test from September 2018 to February 2019 at our hospital. Of the 100 samples, 14 were visually positive and 19 were reader positive. All visually positive samples generated reader positive result. Because 1 of the 5 cases which indicated a negative visual determination and positive reader determination was a sample with strong viscosity and turbidity, it was retested after centrifugation at 3,000×g for 10 min, resulting in negative reader determination. In 2 cases, S. pneumoniae were detected in sputum gram stains and culture tests. 5 discrepant samples were all visually and reader positive after concentration by centrifugal ultrafiltration. A questionnaire about visual interpretation was conducted among 31 individuals, by using urine from day 0 to day 4 collected from the patients whose test result was visually negative, reader positive and sputum culture positive at day 0. As a result, the number of operators who determined visually positive was 0 on day 0 (0%), 16 on day 1 (51.6%), 13 on day 2 (41.9%), 2 on day 3 (6.5%), and 0 on day 4 (0%). There were individual differences in ability to interpret low level positive result visually. On the other hand, reader can remove individual differences among operators from the interpretation of BinaxNOW™ and interpret positive result earlier than visual interpretation. Therefore reader was considered to be useful tool in clinical settings.