No abstract

Pharyngitis in most cases is due to viral microorganisms however drug therapy without the detection of etiological agent leads to unnecessary use of antibiotics. On the other hand, when the etiologic agent is group A beta-hemolytic streptococci (GAS) it is important to identify the etiologic agent rapidly which will guide the treatment with appropriate antibiotics. The use of highly sensitive rapid tests will contribute significantly to early diagnosis and appropriate therapy. The aim of this study is to evaluate the efficacy of Mascia Brunelli rapid antigen test for the detection of GAS in throat swab samples. A total of 833 throat swab samples submitted to our laboratory with pre-diagnosis of pharyngitis were assessed between June 2016 and August 2016. The samples were simultaneously cultured and tested by rapid Mascia Brunelli Strep-A Card (Mascia Brunelli S.p.a, Italy). For identification, bacitracin sensitivity, PYR test and latex agglutination test in addition to Bruker MALDI-TOF MS (Daltonics, Germany) system were used. The density of GAS growth in the culture was noted. The samples that were false negative with Mascia Brunelli test were re-tested with QuickVue + Strep A Test (Quidel Corporation, San Diego, USA) rapid antigen test. A total of 833 patients, 376 (45.2%) female and 457 (54.8%) male were included in the study. The age range was between 0-94 years with a mean value of 7.86 ± 6.72. 125 (15%) and 94 (11.28%) of the samples were positive with culture and rapid antigen test, respectively. Mascia Brunelli antigen test gave negative results for 31 culture positive samples. Of these 31 samples, 28 were found positive by QuickVue + Strep A antigen test. As a result, the sensitivity of the test was found to be independent of the inoculum effect. The culture positivity rate in patients between 5-15 years was 18.4%. The sensitivity, specificity, positive predictive value, negative predictive value and the accuracy of Mascia Brunelli antigen test, with respect to culture, were 75.2%, 100%, 100%, 95.81% and 96.28%, respectively. In conclusion, the selection of rapid antigen tests with high sensitivity in the diagnosis of GAS pharyngitis will contribute to the prevention of resistance development by appropriate use of antibiotics as well as early diagnosis and appropriate treatment. However, confirmation of negative rapid antigen test results by culture is very important in terms of false diagnosis and prevention of incomplete treatment.

Background/aim: We aimed to evaluate the efficacy of a rapid antigen test in detecting group A beta-hemolytic streptococci (GAS) in throat samples in comparison with the culture method and to compare the efficiency of matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) and traditional methods in identifying GAS in cultures. Materials and methods:A total of 3668 throat samples from patients with a prediagnosis of tonsillopharyngitis were assessed by the QuickVue+Strep A antigen test and culture. For GAS identification from cultures, bacitracin sensitivity, PYR, and latex agglutination tests and MALDI-TOF MS were used.Results: A total of 567 (15.5%) and 536 (14.6%) of the samples were positive for GAS culture and rapid antigen testing, respectively. The sensitivity and specificity of the rapid antigen test compared to culture was 89.07% and 99%, respectively, while positive and negative predictive values were 94.22% and 98.02%. Traditional methods were in full concordance with MALDI-TOF-MS for all 567 isolates. In all densities of growth in culture, the time to diagnosis with MALDI-TOF MS was significantly lower than with traditional identification tests. Conclusion:This study shows that both the rapid antigen testing of samples and bacterial identification with MALDI-TOF MS contribute much to the rapid diagnosis of GAS tonsillopharyngitis.