Group A Streptococcus Molecular Point-of-Care Testing: Performance and Assessment of Culture Requirements for Negative Results

• Published in: American journal of clinical pathology 2018-09, Vol.150 (suppl_1), p.S124-S125
• Main Authors: Demkowicz, Ryan, Reineks, Edmunds, Kreller, Robert
• Format: Article
• Language: English
• Subjects: Electronic medical records; Pediatrics; Point of care testing; Streptococcus; Streptococcus infections
• ISSN: 0002-9173; 1943-7722
• DOI: 10.1093/ajcp/aqy101.298

Abstract Introduction Point-of-care testing (POCT) for the diagnosis of group A Streptococcus (GAS) is an established practice. The standard method has been the rapid antigen detection test. Due to a variable sensitivity, manufacturers have stated that negative results should be confirmed with culture; however, as techniques have improved, current clinical guidelines state that this culture may not be necessary in most adults. Molecular techniques are now available with higher sensitivity and specificity. We performed a 1-year review of our point-of-care molecular GAS testing to assess performance characteristics that will help inform our decision on the need for confirmatory cultures. Methods Resulted point-of-care GAS cases using the Alere i platform (Abbott Laboratories, Chicago, IL) were reviewed using the electronic medical record and test logs from January 1, 2017, to December 31, 2017. Corresponding data on bacterial cultures were also gathered. The sensitivity and the negative predictive value were calculated using culture as the gold standard and accepting molecular positive tests as true positives. Results A total of 718 cases were reviewed; 434 (60%) adults and 284 (40%) pediatric patients were included in the study, 153 (21%) were positive on molecular POCT, and 565 (79%) tested negative, 342 of whom were sent for confirmatory culture. Only one of the 342 negative cases was positive by culture. Sensitivity is calculated as 99.3% with a negative predictive value of 99.7%. Conclusions Our results show that molecular POCT is an excellent screening method for GAS in a population of both adults and children. There was only one false negative in the cases with confirmatory cultures, suggesting that these cultures may not be required. Larger studies may be needed to determine whether the high sensitivity and negative predictive values are stable with a solely pediatric population.